2022-11-05 00:44:03

by Lyude Paul

[permalink] [raw]
Subject: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

It appears that amdgpu makes the mistake of completely ignoring the return
values from the DP MST helpers, and instead just returns a simple
true/false. In this case, it seems to have come back to bite us because as
a result of simply returning false from
compute_mst_dsc_configs_for_state(), amdgpu had no way of telling when a
deadlock happened from these helpers. This could definitely result in some
kernel splats.

Signed-off-by: Lyude Paul <[email protected]>
Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
Cc: Harry Wentland <[email protected]>
Cc: <[email protected]> # v5.6+
---
.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +--
.../display/amdgpu_dm/amdgpu_dm_mst_types.c | 107 ++++++++++--------
.../display/amdgpu_dm/amdgpu_dm_mst_types.h | 12 +-
3 files changed, 73 insertions(+), 64 deletions(-)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 0db2a88cd4d7b..6f76b2c84cdb5 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6462,7 +6462,7 @@ static int dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
struct drm_connector_state *new_con_state;
struct amdgpu_dm_connector *aconnector;
struct dm_connector_state *dm_conn_state;
- int i, j;
+ int i, j, ret;
int vcpi, pbn_div, pbn, slot_num = 0;

for_each_new_connector_in_state(state, connector, new_con_state, i) {
@@ -6509,8 +6509,11 @@ static int dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
dm_conn_state->pbn = pbn;
dm_conn_state->vcpi_slots = slot_num;

- drm_dp_mst_atomic_enable_dsc(state, aconnector->port, dm_conn_state->pbn,
- false);
+ ret = drm_dp_mst_atomic_enable_dsc(state, aconnector->port,
+ dm_conn_state->pbn, false);
+ if (ret != 0)
+ return ret;
+
continue;
}

@@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,

#if defined(CONFIG_DRM_AMD_DC_DCN)
if (dc_resource_is_dsc_encoding_supported(dc)) {
- if (!pre_validate_dsc(state, &dm_state, vars)) {
- ret = -EINVAL;
+ ret = pre_validate_dsc(state, &dm_state, vars);
+ if (ret != 0)
goto fail;
- }
}
#endif

@@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct drm_device *dev,
}

#if defined(CONFIG_DRM_AMD_DC_DCN)
- if (!compute_mst_dsc_configs_for_state(state, dm_state->context, vars)) {
+ ret = compute_mst_dsc_configs_for_state(state, dm_state->context, vars);
+ if (ret) {
DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state() failed\n");
- ret = -EINVAL;
goto fail;
}

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
index 6ff96b4bdda5c..30bc2e5058b70 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
@@ -864,25 +864,25 @@ static bool try_disable_dsc(struct drm_atomic_state *state,
return true;
}

-static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
- struct dc_state *dc_state,
- struct dc_link *dc_link,
- struct dsc_mst_fairness_vars *vars,
- struct drm_dp_mst_topology_mgr *mgr,
- int *link_vars_start_index)
+static int compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
+ struct dc_state *dc_state,
+ struct dc_link *dc_link,
+ struct dsc_mst_fairness_vars *vars,
+ struct drm_dp_mst_topology_mgr *mgr,
+ int *link_vars_start_index)
{
struct dc_stream_state *stream;
struct dsc_mst_fairness_params params[MAX_PIPES];
struct amdgpu_dm_connector *aconnector;
struct drm_dp_mst_topology_state *mst_state = drm_atomic_get_mst_topology_state(state, mgr);
int count = 0;
- int i, k;
+ int i, k, ret;
bool debugfs_overwrite = false;

memset(params, 0, sizeof(params));

if (IS_ERR(mst_state))
- return false;
+ return PTR_ERR(mst_state);

mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link);
#if defined(CONFIG_DRM_AMD_DC_DCN)
@@ -933,7 +933,7 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,

if (count == 0) {
ASSERT(0);
- return true;
+ return 0;
}

/* k is start index of vars for current phy link used by mst hub */
@@ -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
vars[i + k].bpp_x16 = 0;
if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr, params[i].port,
vars[i + k].pbn) < 0)
- return false;
+ return -EINVAL;
}
- if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
+ ret = drm_dp_mst_atomic_check(state);
+ if (ret == 0 && !debugfs_overwrite) {
set_dsc_configs_from_fairness_vars(params, vars, count, k);
- return true;
+ return 0;
+ } else if (ret == -EDEADLK) {
+ return ret;
}

/* Try max compression */
@@ -964,29 +967,30 @@ static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
vars[i + k].bpp_x16 = params[i].bw_range.min_target_bpp_x16;
if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
params[i].port, vars[i + k].pbn) < 0)
- return false;
+ return -EINVAL;
} else {
vars[i + k].pbn = kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
vars[i + k].dsc_enabled = false;
vars[i + k].bpp_x16 = 0;
if (drm_dp_atomic_find_time_slots(state, params[i].port->mgr,
params[i].port, vars[i + k].pbn) < 0)
- return false;
+ return -EINVAL;
}
}
- if (drm_dp_mst_atomic_check(state))
- return false;
+ ret = drm_dp_mst_atomic_check(state);
+ if (ret != 0)
+ return ret;

/* Optimize degree of compression */
if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count, k))
- return false;
+ return -ENOSPC;

if (!try_disable_dsc(state, dc_link, params, vars, count, k))
- return false;
+ return -ENOSPC;

set_dsc_configs_from_fairness_vars(params, vars, count, k);

- return true;
+ return 0;
}

static bool is_dsc_need_re_compute(
@@ -1087,15 +1091,16 @@ static bool is_dsc_need_re_compute(
return is_dsc_need_re_compute;
}

-bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
- struct dc_state *dc_state,
- struct dsc_mst_fairness_vars *vars)
+int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
+ struct dc_state *dc_state,
+ struct dsc_mst_fairness_vars *vars)
{
int i, j;
struct dc_stream_state *stream;
bool computed_streams[MAX_PIPES];
struct amdgpu_dm_connector *aconnector;
int link_vars_start_index = 0;
+ int ret = 0;

for (i = 0; i < dc_state->stream_count; i++)
computed_streams[i] = false;
@@ -1118,17 +1123,19 @@ bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
continue;

if (dcn20_remove_stream_from_ctx(stream->ctx->dc, dc_state, stream) != DC_OK)
- return false;
+ return -EINVAL;

if (!is_dsc_need_re_compute(state, dc_state, stream->link))
continue;

mutex_lock(&aconnector->mst_mgr.lock);
- if (!compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
- &aconnector->mst_mgr,
- &link_vars_start_index)) {
+
+ ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
+ &aconnector->mst_mgr,
+ &link_vars_start_index);
+ if (ret != 0) {
mutex_unlock(&aconnector->mst_mgr.lock);
- return false;
+ return ret;
}
mutex_unlock(&aconnector->mst_mgr.lock);

@@ -1143,22 +1150,22 @@ bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,

if (stream->timing.flags.DSC == 1)
if (dc_stream_add_dsc_to_resource(stream->ctx->dc, dc_state, stream) != DC_OK)
- return false;
+ return -EINVAL;
}

- return true;
+ return ret;
}

-static bool
- pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
- struct dc_state *dc_state,
- struct dsc_mst_fairness_vars *vars)
+static int pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
+ struct dc_state *dc_state,
+ struct dsc_mst_fairness_vars *vars)
{
int i, j;
struct dc_stream_state *stream;
bool computed_streams[MAX_PIPES];
struct amdgpu_dm_connector *aconnector;
int link_vars_start_index = 0;
+ int ret;

for (i = 0; i < dc_state->stream_count; i++)
computed_streams[i] = false;
@@ -1184,13 +1191,12 @@ static bool
continue;

mutex_lock(&aconnector->mst_mgr.lock);
- if (!compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
- &aconnector->mst_mgr,
- &link_vars_start_index)) {
- mutex_unlock(&aconnector->mst_mgr.lock);
- return false;
- }
+ ret = compute_mst_dsc_configs_for_link(state, dc_state, stream->link, vars,
+ &aconnector->mst_mgr,
+ &link_vars_start_index);
mutex_unlock(&aconnector->mst_mgr.lock);
+ if (ret != 0)
+ return ret;

for (j = 0; j < dc_state->stream_count; j++) {
if (dc_state->streams[j]->link == stream->link)
@@ -1198,7 +1204,7 @@ static bool
}
}

- return true;
+ return ret;
}

static int find_crtc_index_in_state_by_stream(struct drm_atomic_state *state,
@@ -1253,9 +1259,9 @@ static bool is_dsc_precompute_needed(struct drm_atomic_state *state)
return ret;
}

-bool pre_validate_dsc(struct drm_atomic_state *state,
- struct dm_atomic_state **dm_state_ptr,
- struct dsc_mst_fairness_vars *vars)
+int pre_validate_dsc(struct drm_atomic_state *state,
+ struct dm_atomic_state **dm_state_ptr,
+ struct dsc_mst_fairness_vars *vars)
{
int i;
struct dm_atomic_state *dm_state;
@@ -1264,11 +1270,12 @@ bool pre_validate_dsc(struct drm_atomic_state *state,

if (!is_dsc_precompute_needed(state)) {
DRM_INFO_ONCE("DSC precompute is not needed.\n");
- return true;
+ return 0;
}
- if (dm_atomic_get_state(state, dm_state_ptr)) {
+ ret = dm_atomic_get_state(state, dm_state_ptr);
+ if (ret != 0) {
DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
- return false;
+ return ret;
}
dm_state = *dm_state_ptr;

@@ -1280,7 +1287,7 @@ bool pre_validate_dsc(struct drm_atomic_state *state,

local_dc_state = kmemdup(dm_state->context, sizeof(struct dc_state), GFP_KERNEL);
if (!local_dc_state)
- return false;
+ return -ENOMEM;

for (i = 0; i < local_dc_state->stream_count; i++) {
struct dc_stream_state *stream = dm_state->context->streams[i];
@@ -1316,9 +1323,9 @@ bool pre_validate_dsc(struct drm_atomic_state *state,
if (ret != 0)
goto clean_exit;

- if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state, vars)) {
+ ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state, vars);
+ if (ret != 0) {
DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state() failed\n");
- ret = -EINVAL;
goto clean_exit;
}

@@ -1349,7 +1356,7 @@ bool pre_validate_dsc(struct drm_atomic_state *state,

kfree(local_dc_state);

- return (ret == 0);
+ return ret;
}

static unsigned int kbps_from_pbn(unsigned int pbn)
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
index b92a7c5671aa2..97fd70df531bf 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
@@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
struct amdgpu_dm_connector *aconnector;
};

-bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
- struct dc_state *dc_state,
- struct dsc_mst_fairness_vars *vars);
+int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
+ struct dc_state *dc_state,
+ struct dsc_mst_fairness_vars *vars);

bool needs_dsc_aux_workaround(struct dc_link *link);

-bool pre_validate_dsc(struct drm_atomic_state *state,
- struct dm_atomic_state **dm_state_ptr,
- struct dsc_mst_fairness_vars *vars);
+int pre_validate_dsc(struct drm_atomic_state *state,
+ struct dm_atomic_state **dm_state_ptr,
+ struct dsc_mst_fairness_vars *vars);

enum dc_status dm_dp_mst_is_port_support_mode(
struct amdgpu_dm_connector *aconnector,
--
2.37.3



2022-11-09 10:52:55

by Lin, Wayne

[permalink] [raw]
Subject: RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Public]

Thanks, Lyude!
Comments inline.

> -----Original Message-----
> From: Lyude Paul <[email protected]>
> Sent: Saturday, November 5, 2022 7:59 AM
> To: [email protected]
> Cc: Wentland, Harry <[email protected]>; [email protected];
> Li, Sun peng (Leo) <[email protected]>; Siqueira, Rodrigo
> <[email protected]>; Deucher, Alexander
> <[email protected]>; Koenig, Christian
> <[email protected]>; Pan, Xinhui <[email protected]>; David
> Airlie <[email protected]>; Daniel Vetter <[email protected]>; Kazlauskas,
> Nicholas <[email protected]>; Pillai, Aurabindo
> <[email protected]>; Li, Roman <[email protected]>; Zuo, Jerry
> <[email protected]>; Wu, Hersen <[email protected]>; Lin, Wayne
> <[email protected]>; Thomas Zimmermann <[email protected]>;
> Mahfooz, Hamza <[email protected]>; Hung, Alex
> <[email protected]>; Francis, David <[email protected]>; Mikita
> Lipski <[email protected]>; Liu, Wenjing <[email protected]>;
> open list:DRM DRIVERS <[email protected]>; open list <linux-
> [email protected]>
> Subject: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
>
> It appears that amdgpu makes the mistake of completely ignoring the return
> values from the DP MST helpers, and instead just returns a simple true/false.
> In this case, it seems to have come back to bite us because as a result of
> simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> had no way of telling when a deadlock happened from these helpers. This
> could definitely result in some kernel splats.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> Cc: Harry Wentland <[email protected]>
> Cc: <[email protected]> # v5.6+
> ---
> .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +--
> .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 107 ++++++++++------
> --
> .../display/amdgpu_dm/amdgpu_dm_mst_types.h | 12 +-
> 3 files changed, 73 insertions(+), 64 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 0db2a88cd4d7b..6f76b2c84cdb5 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -6462,7 +6462,7 @@ static int
> dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> struct drm_connector_state *new_con_state;
> struct amdgpu_dm_connector *aconnector;
> struct dm_connector_state *dm_conn_state;
> - int i, j;
> + int i, j, ret;
> int vcpi, pbn_div, pbn, slot_num = 0;
>
> for_each_new_connector_in_state(state, connector,
> new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> dm_conn_state->pbn = pbn;
> dm_conn_state->vcpi_slots = slot_num;
>
> - drm_dp_mst_atomic_enable_dsc(state, aconnector-
> >port, dm_conn_state->pbn,
> - false);
> + ret = drm_dp_mst_atomic_enable_dsc(state,
> aconnector->port,
> + dm_conn_state-
> >pbn, false);
> + if (ret != 0)
> + return ret;
> +
> continue;
> }
>
> @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> drm_device *dev,
>
> #if defined(CONFIG_DRM_AMD_DC_DCN)
> if (dc_resource_is_dsc_encoding_supported(dc)) {
> - if (!pre_validate_dsc(state, &dm_state, vars)) {
> - ret = -EINVAL;
> + ret = pre_validate_dsc(state, &dm_state, vars);
> + if (ret != 0)
> goto fail;
> - }
> }
> #endif
>
> @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> drm_device *dev,
> }
>
> #if defined(CONFIG_DRM_AMD_DC_DCN)
> - if (!compute_mst_dsc_configs_for_state(state, dm_state-
> >context, vars)) {
> + ret = compute_mst_dsc_configs_for_state(state, dm_state-
> >context, vars);
> + if (ret) {
>
> DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> failed\n");
> - ret = -EINVAL;
> goto fail;
> }
>
> diff --git
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> index 6ff96b4bdda5c..30bc2e5058b70 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> +++
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> @@ -864,25 +864,25 @@ static bool try_disable_dsc(struct
> drm_atomic_state *state,
> return true;
> }
>
> -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> *state,
> - struct dc_state *dc_state,
> - struct dc_link *dc_link,
> - struct dsc_mst_fairness_vars *vars,
> - struct drm_dp_mst_topology_mgr
> *mgr,
> - int *link_vars_start_index)
> +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> *state,
> + struct dc_state *dc_state,
> + struct dc_link *dc_link,
> + struct dsc_mst_fairness_vars *vars,
> + struct drm_dp_mst_topology_mgr
> *mgr,
> + int *link_vars_start_index)
> {
> struct dc_stream_state *stream;
> struct dsc_mst_fairness_params params[MAX_PIPES];
> struct amdgpu_dm_connector *aconnector;
> struct drm_dp_mst_topology_state *mst_state =
> drm_atomic_get_mst_topology_state(state, mgr);
> int count = 0;
> - int i, k;
> + int i, k, ret;
> bool debugfs_overwrite = false;
>
> memset(params, 0, sizeof(params));
>
> if (IS_ERR(mst_state))
> - return false;
> + return PTR_ERR(mst_state);
>
> mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link); #if
> defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +933,7 @@ static bool
> compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
>
> if (count == 0) {
> ASSERT(0);
> - return true;
> + return 0;
> }
>
> /* k is start index of vars for current phy link used by mst hub */ @@
> -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct
> drm_atomic_state *state,
> vars[i + k].bpp_x16 = 0;
> if (drm_dp_atomic_find_time_slots(state, params[i].port-
> >mgr, params[i].port,
> vars[i + k].pbn) < 0)
> - return false;
> + return -EINVAL;

Should we also return the error code get from drm_dp_atomic_find_time_slots() rather than
assigning a new one here?

> }
> - if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> + ret = drm_dp_mst_atomic_check(state);
> + if (ret == 0 && !debugfs_overwrite) {
> set_dsc_configs_from_fairness_vars(params, vars, count, k);
> - return true;
> + return 0;
> + } else if (ret == -EDEADLK) {
> + return ret;

I think we should return here whenever there is an error. Not just for EDEADLK case.

> }
>
> /* Try max compression */
> @@ -964,29 +967,30 @@ static bool
> compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> vars[i + k].bpp_x16 =
> params[i].bw_range.min_target_bpp_x16;
> if (drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> params[i].port, vars[i
> + k].pbn) < 0)
> - return false;
> + return -EINVAL;

Same as above.

> } else {
> vars[i + k].pbn =
> kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> vars[i + k].dsc_enabled = false;
> vars[i + k].bpp_x16 = 0;
> if (drm_dp_atomic_find_time_slots(state,
> params[i].port->mgr,
> params[i].port, vars[i
> + k].pbn) < 0)
> - return false;
> + return -EINVAL;

Same as above.

> }
> }
> - if (drm_dp_mst_atomic_check(state))
> - return false;
> + ret = drm_dp_mst_atomic_check(state);
> + if (ret != 0)
> + return ret;
>
> /* Optimize degree of compression */
> if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> k))
> - return false;
> + return -ENOSPC;
>
> if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> - return false;
> + return -ENOSPC;
>
> set_dsc_configs_from_fairness_vars(params, vars, count, k);
>
> - return true;
> + return 0;
> }
>
> static bool is_dsc_need_re_compute(
> @@ -1087,15 +1091,16 @@ static bool is_dsc_need_re_compute(
> return is_dsc_need_re_compute;
> }
>
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> - struct dc_state *dc_state,
> - struct dsc_mst_fairness_vars *vars)
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> + struct dc_state *dc_state,
> + struct dsc_mst_fairness_vars *vars)
> {
> int i, j;
> struct dc_stream_state *stream;
> bool computed_streams[MAX_PIPES];
> struct amdgpu_dm_connector *aconnector;
> int link_vars_start_index = 0;
> + int ret = 0;
>
> for (i = 0; i < dc_state->stream_count; i++)
> computed_streams[i] = false;
> @@ -1118,17 +1123,19 @@ bool compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
> continue;
>
> if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> dc_state, stream) != DC_OK)
> - return false;
> + return -EINVAL;
>
> if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> continue;
>
> mutex_lock(&aconnector->mst_mgr.lock);
> - if (!compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> - &aconnector->mst_mgr,
> - &link_vars_start_index)) {
> +
> + ret = compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> + &aconnector->mst_mgr,
> + &link_vars_start_index);
> + if (ret != 0) {
> mutex_unlock(&aconnector->mst_mgr.lock);
> - return false;
> + return ret;
> }
> mutex_unlock(&aconnector->mst_mgr.lock);
>
> @@ -1143,22 +1150,22 @@ bool compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
>
> if (stream->timing.flags.DSC == 1)
> if (dc_stream_add_dsc_to_resource(stream->ctx-
> >dc, dc_state, stream) != DC_OK)
> - return false;
> + return -EINVAL;
> }
>
> - return true;
> + return ret;
> }
>
> -static bool
> - pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> *state,
> - struct dc_state *dc_state,
> - struct dsc_mst_fairness_vars
> *vars)
> +static int pre_compute_mst_dsc_configs_for_state(struct
> drm_atomic_state *state,
> + struct dc_state *dc_state,
> + struct dsc_mst_fairness_vars
> *vars)
> {
> int i, j;
> struct dc_stream_state *stream;
> bool computed_streams[MAX_PIPES];
> struct amdgpu_dm_connector *aconnector;
> int link_vars_start_index = 0;
> + int ret;
>
> for (i = 0; i < dc_state->stream_count; i++)
> computed_streams[i] = false;
> @@ -1184,13 +1191,12 @@ static bool
> continue;
>
> mutex_lock(&aconnector->mst_mgr.lock);
> - if (!compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> - &aconnector->mst_mgr,
> - &link_vars_start_index)) {
> - mutex_unlock(&aconnector->mst_mgr.lock);
> - return false;
> - }
> + ret = compute_mst_dsc_configs_for_link(state, dc_state,
> stream->link, vars,
> + &aconnector->mst_mgr,
> + &link_vars_start_index);
> mutex_unlock(&aconnector->mst_mgr.lock);
> + if (ret != 0)
> + return ret;
>
> for (j = 0; j < dc_state->stream_count; j++) {
> if (dc_state->streams[j]->link == stream->link) @@ -
> 1198,7 +1204,7 @@ static bool
> }
> }
>
> - return true;
> + return ret;
> }
>
> static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> *state, @@ -1253,9 +1259,9 @@ static bool
> is_dsc_precompute_needed(struct drm_atomic_state *state)
> return ret;
> }
>
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> - struct dm_atomic_state **dm_state_ptr,
> - struct dsc_mst_fairness_vars *vars)
> +int pre_validate_dsc(struct drm_atomic_state *state,
> + struct dm_atomic_state **dm_state_ptr,
> + struct dsc_mst_fairness_vars *vars)
> {
> int i;
> struct dm_atomic_state *dm_state;
> @@ -1264,11 +1270,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
>
> if (!is_dsc_precompute_needed(state)) {
> DRM_INFO_ONCE("DSC precompute is not needed.\n");
> - return true;
> + return 0;
> }
> - if (dm_atomic_get_state(state, dm_state_ptr)) {
> + ret = dm_atomic_get_state(state, dm_state_ptr);
> + if (ret != 0) {
> DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> - return false;
> + return ret;
> }
> dm_state = *dm_state_ptr;
>
> @@ -1280,7 +1287,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
>
> local_dc_state = kmemdup(dm_state->context, sizeof(struct
> dc_state), GFP_KERNEL);
> if (!local_dc_state)
> - return false;
> + return -ENOMEM;
>
> for (i = 0; i < local_dc_state->stream_count; i++) {
> struct dc_stream_state *stream = dm_state->context-
> >streams[i]; @@ -1316,9 +1323,9 @@ bool pre_validate_dsc(struct
> drm_atomic_state *state,
> if (ret != 0)
> goto clean_exit;
>
> - if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> vars)) {
> + ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> vars);
> + if (ret != 0) {
>
> DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> failed\n");
> - ret = -EINVAL;
> goto clean_exit;
> }
>
> @@ -1349,7 +1356,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> *state,
>
> kfree(local_dc_state);
>
> - return (ret == 0);
> + return ret;
> }
>
> static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> index b92a7c5671aa2..97fd70df531bf 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> +++
> b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> struct amdgpu_dm_connector *aconnector; };
>
> -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> - struct dc_state *dc_state,
> - struct dsc_mst_fairness_vars *vars);
> +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> + struct dc_state *dc_state,
> + struct dsc_mst_fairness_vars *vars);
>
> bool needs_dsc_aux_workaround(struct dc_link *link);
>
> -bool pre_validate_dsc(struct drm_atomic_state *state,
> - struct dm_atomic_state **dm_state_ptr,
> - struct dsc_mst_fairness_vars *vars);
> +int pre_validate_dsc(struct drm_atomic_state *state,
> + struct dm_atomic_state **dm_state_ptr,
> + struct dsc_mst_fairness_vars *vars);
>
> enum dc_status dm_dp_mst_is_port_support_mode(
> struct amdgpu_dm_connector *aconnector,
> --
> 2.37.3
---
Regards,
Wayne Lin

2022-11-14 21:40:42

by Lyude Paul

[permalink] [raw]
Subject: Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> [Public]
>
> Thanks, Lyude!
> Comments inline.
>
> > -----Original Message-----
> > From: Lyude Paul <[email protected]>
> > Sent: Saturday, November 5, 2022 7:59 AM
> > To: [email protected]
> > Cc: Wentland, Harry <[email protected]>; [email protected];
> > Li, Sun peng (Leo) <[email protected]>; Siqueira, Rodrigo
> > <[email protected]>; Deucher, Alexander
> > <[email protected]>; Koenig, Christian
> > <[email protected]>; Pan, Xinhui <[email protected]>; David
> > Airlie <[email protected]>; Daniel Vetter <[email protected]>; Kazlauskas,
> > Nicholas <[email protected]>; Pillai, Aurabindo
> > <[email protected]>; Li, Roman <[email protected]>; Zuo, Jerry
> > <[email protected]>; Wu, Hersen <[email protected]>; Lin, Wayne
> > <[email protected]>; Thomas Zimmermann <[email protected]>;
> > Mahfooz, Hamza <[email protected]>; Hung, Alex
> > <[email protected]>; Francis, David <[email protected]>; Mikita
> > Lipski <[email protected]>; Liu, Wenjing <[email protected]>;
> > open list:DRM DRIVERS <[email protected]>; open list <linux-
> > [email protected]>
> > Subject: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> > deadlocking
> >
> > It appears that amdgpu makes the mistake of completely ignoring the return
> > values from the DP MST helpers, and instead just returns a simple true/false.
> > In this case, it seems to have come back to bite us because as a result of
> > simply returning false from compute_mst_dsc_configs_for_state(), amdgpu
> > had no way of telling when a deadlock happened from these helpers. This
> > could definitely result in some kernel splats.
> >
> > Signed-off-by: Lyude Paul <[email protected]>
> > Fixes: 8c20a1ed9b4f ("drm/amd/display: MST DSC compute fair share")
> > Cc: Harry Wentland <[email protected]>
> > Cc: <[email protected]> # v5.6+
> > ---
> > .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +--
> > .../display/amdgpu_dm/amdgpu_dm_mst_types.c | 107 ++++++++++------
> > --
> > .../display/amdgpu_dm/amdgpu_dm_mst_types.h | 12 +-
> > 3 files changed, 73 insertions(+), 64 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > index 0db2a88cd4d7b..6f76b2c84cdb5 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> > @@ -6462,7 +6462,7 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > struct drm_connector_state *new_con_state;
> > struct amdgpu_dm_connector *aconnector;
> > struct dm_connector_state *dm_conn_state;
> > - int i, j;
> > + int i, j, ret;
> > int vcpi, pbn_div, pbn, slot_num = 0;
> >
> > for_each_new_connector_in_state(state, connector,
> > new_con_state, i) { @@ -6509,8 +6509,11 @@ static int
> > dm_update_mst_vcpi_slots_for_dsc(struct drm_atomic_state *state,
> > dm_conn_state->pbn = pbn;
> > dm_conn_state->vcpi_slots = slot_num;
> >
> > - drm_dp_mst_atomic_enable_dsc(state, aconnector-
> > > port, dm_conn_state->pbn,
> > - false);
> > + ret = drm_dp_mst_atomic_enable_dsc(state,
> > aconnector->port,
> > + dm_conn_state-
> > > pbn, false);
> > + if (ret != 0)
> > + return ret;
> > +
> > continue;
> > }
> >
> > @@ -9523,10 +9526,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> >
> > #if defined(CONFIG_DRM_AMD_DC_DCN)
> > if (dc_resource_is_dsc_encoding_supported(dc)) {
> > - if (!pre_validate_dsc(state, &dm_state, vars)) {
> > - ret = -EINVAL;
> > + ret = pre_validate_dsc(state, &dm_state, vars);
> > + if (ret != 0)
> > goto fail;
> > - }
> > }
> > #endif
> >
> > @@ -9621,9 +9623,9 @@ static int amdgpu_dm_atomic_check(struct
> > drm_device *dev,
> > }
> >
> > #if defined(CONFIG_DRM_AMD_DC_DCN)
> > - if (!compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars)) {
> > + ret = compute_mst_dsc_configs_for_state(state, dm_state-
> > > context, vars);
> > + if (ret) {
> >
> > DRM_DEBUG_DRIVER("compute_mst_dsc_configs_for_state()
> > failed\n");
> > - ret = -EINVAL;
> > goto fail;
> > }
> >
> > diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > index 6ff96b4bdda5c..30bc2e5058b70 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.c
> > @@ -864,25 +864,25 @@ static bool try_disable_dsc(struct
> > drm_atomic_state *state,
> > return true;
> > }
> >
> > -static bool compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > - struct dc_state *dc_state,
> > - struct dc_link *dc_link,
> > - struct dsc_mst_fairness_vars *vars,
> > - struct drm_dp_mst_topology_mgr
> > *mgr,
> > - int *link_vars_start_index)
> > +static int compute_mst_dsc_configs_for_link(struct drm_atomic_state
> > *state,
> > + struct dc_state *dc_state,
> > + struct dc_link *dc_link,
> > + struct dsc_mst_fairness_vars *vars,
> > + struct drm_dp_mst_topology_mgr
> > *mgr,
> > + int *link_vars_start_index)
> > {
> > struct dc_stream_state *stream;
> > struct dsc_mst_fairness_params params[MAX_PIPES];
> > struct amdgpu_dm_connector *aconnector;
> > struct drm_dp_mst_topology_state *mst_state =
> > drm_atomic_get_mst_topology_state(state, mgr);
> > int count = 0;
> > - int i, k;
> > + int i, k, ret;
> > bool debugfs_overwrite = false;
> >
> > memset(params, 0, sizeof(params));
> >
> > if (IS_ERR(mst_state))
> > - return false;
> > + return PTR_ERR(mst_state);
> >
> > mst_state->pbn_div = dm_mst_get_pbn_divider(dc_link); #if
> > defined(CONFIG_DRM_AMD_DC_DCN) @@ -933,7 +933,7 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> >
> > if (count == 0) {
> > ASSERT(0);
> > - return true;
> > + return 0;
> > }
> >
> > /* k is start index of vars for current phy link used by mst hub */ @@
> > -949,11 +949,14 @@ static bool compute_mst_dsc_configs_for_link(struct
> > drm_atomic_state *state,
> > vars[i + k].bpp_x16 = 0;
> > if (drm_dp_atomic_find_time_slots(state, params[i].port-
> > > mgr, params[i].port,
> > vars[i + k].pbn) < 0)
> > - return false;
> > + return -EINVAL;
>
> Should we also return the error code get from drm_dp_atomic_find_time_slots() rather than
> assigning a new one here?

Yes we should, nice catch!

>
> > }
> > - if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > + ret = drm_dp_mst_atomic_check(state);
> > + if (ret == 0 && !debugfs_overwrite) {
> > set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > - return true;
> > + return 0;
> > + } else if (ret == -EDEADLK) {
> > + return ret;
>
> I think we should return here whenever there is an error. Not just for EDEADLK case.

sgtm


>
> > }
> >
> > /* Try max compression */
> > @@ -964,29 +967,30 @@ static bool
> > compute_mst_dsc_configs_for_link(struct drm_atomic_state *state,
> > vars[i + k].bpp_x16 =
> > params[i].bw_range.min_target_bpp_x16;
> > if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > params[i].port, vars[i
> > + k].pbn) < 0)
> > - return false;
> > + return -EINVAL;
>
> Same as above.
>
> > } else {
> > vars[i + k].pbn =
> > kbps_to_peak_pbn(params[i].bw_range.stream_kbps);
> > vars[i + k].dsc_enabled = false;
> > vars[i + k].bpp_x16 = 0;
> > if (drm_dp_atomic_find_time_slots(state,
> > params[i].port->mgr,
> > params[i].port, vars[i
> > + k].pbn) < 0)
> > - return false;
> > + return -EINVAL;
>
> Same as above.
>
> > }
> > }
> > - if (drm_dp_mst_atomic_check(state))
> > - return false;
> > + ret = drm_dp_mst_atomic_check(state);
> > + if (ret != 0)
> > + return ret;
> >
> > /* Optimize degree of compression */
> > if (!increase_dsc_bpp(state, mst_state, dc_link, params, vars, count,
> > k))
> > - return false;
> > + return -ENOSPC;
> >
> > if (!try_disable_dsc(state, dc_link, params, vars, count, k))
> > - return false;
> > + return -ENOSPC;
> >
> > set_dsc_configs_from_fairness_vars(params, vars, count, k);
> >
> > - return true;
> > + return 0;
> > }
> >
> > static bool is_dsc_need_re_compute(
> > @@ -1087,15 +1091,16 @@ static bool is_dsc_need_re_compute(
> > return is_dsc_need_re_compute;
> > }
> >
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > - struct dc_state *dc_state,
> > - struct dsc_mst_fairness_vars *vars)
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > + struct dc_state *dc_state,
> > + struct dsc_mst_fairness_vars *vars)
> > {
> > int i, j;
> > struct dc_stream_state *stream;
> > bool computed_streams[MAX_PIPES];
> > struct amdgpu_dm_connector *aconnector;
> > int link_vars_start_index = 0;
> > + int ret = 0;
> >
> > for (i = 0; i < dc_state->stream_count; i++)
> > computed_streams[i] = false;
> > @@ -1118,17 +1123,19 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > continue;
> >
> > if (dcn20_remove_stream_from_ctx(stream->ctx->dc,
> > dc_state, stream) != DC_OK)
> > - return false;
> > + return -EINVAL;
> >
> > if (!is_dsc_need_re_compute(state, dc_state, stream->link))
> > continue;
> >
> > mutex_lock(&aconnector->mst_mgr.lock);
> > - if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > - &aconnector->mst_mgr,
> > - &link_vars_start_index)) {
> > +
> > + ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > + &aconnector->mst_mgr,
> > + &link_vars_start_index);
> > + if (ret != 0) {
> > mutex_unlock(&aconnector->mst_mgr.lock);
> > - return false;
> > + return ret;
> > }
> > mutex_unlock(&aconnector->mst_mgr.lock);
> >
> > @@ -1143,22 +1150,22 @@ bool compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> >
> > if (stream->timing.flags.DSC == 1)
> > if (dc_stream_add_dsc_to_resource(stream->ctx-
> > > dc, dc_state, stream) != DC_OK)
> > - return false;
> > + return -EINVAL;
> > }
> >
> > - return true;
> > + return ret;
> > }
> >
> > -static bool
> > - pre_compute_mst_dsc_configs_for_state(struct drm_atomic_state
> > *state,
> > - struct dc_state *dc_state,
> > - struct dsc_mst_fairness_vars
> > *vars)
> > +static int pre_compute_mst_dsc_configs_for_state(struct
> > drm_atomic_state *state,
> > + struct dc_state *dc_state,
> > + struct dsc_mst_fairness_vars
> > *vars)
> > {
> > int i, j;
> > struct dc_stream_state *stream;
> > bool computed_streams[MAX_PIPES];
> > struct amdgpu_dm_connector *aconnector;
> > int link_vars_start_index = 0;
> > + int ret;
> >
> > for (i = 0; i < dc_state->stream_count; i++)
> > computed_streams[i] = false;
> > @@ -1184,13 +1191,12 @@ static bool
> > continue;
> >
> > mutex_lock(&aconnector->mst_mgr.lock);
> > - if (!compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > - &aconnector->mst_mgr,
> > - &link_vars_start_index)) {
> > - mutex_unlock(&aconnector->mst_mgr.lock);
> > - return false;
> > - }
> > + ret = compute_mst_dsc_configs_for_link(state, dc_state,
> > stream->link, vars,
> > + &aconnector->mst_mgr,
> > + &link_vars_start_index);
> > mutex_unlock(&aconnector->mst_mgr.lock);
> > + if (ret != 0)
> > + return ret;
> >
> > for (j = 0; j < dc_state->stream_count; j++) {
> > if (dc_state->streams[j]->link == stream->link) @@ -
> > 1198,7 +1204,7 @@ static bool
> > }
> > }
> >
> > - return true;
> > + return ret;
> > }
> >
> > static int find_crtc_index_in_state_by_stream(struct drm_atomic_state
> > *state, @@ -1253,9 +1259,9 @@ static bool
> > is_dsc_precompute_needed(struct drm_atomic_state *state)
> > return ret;
> > }
> >
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > - struct dm_atomic_state **dm_state_ptr,
> > - struct dsc_mst_fairness_vars *vars)
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > + struct dm_atomic_state **dm_state_ptr,
> > + struct dsc_mst_fairness_vars *vars)
> > {
> > int i;
> > struct dm_atomic_state *dm_state;
> > @@ -1264,11 +1270,12 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> >
> > if (!is_dsc_precompute_needed(state)) {
> > DRM_INFO_ONCE("DSC precompute is not needed.\n");
> > - return true;
> > + return 0;
> > }
> > - if (dm_atomic_get_state(state, dm_state_ptr)) {
> > + ret = dm_atomic_get_state(state, dm_state_ptr);
> > + if (ret != 0) {
> > DRM_INFO_ONCE("dm_atomic_get_state() failed\n");
> > - return false;
> > + return ret;
> > }
> > dm_state = *dm_state_ptr;
> >
> > @@ -1280,7 +1287,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> >
> > local_dc_state = kmemdup(dm_state->context, sizeof(struct
> > dc_state), GFP_KERNEL);
> > if (!local_dc_state)
> > - return false;
> > + return -ENOMEM;
> >
> > for (i = 0; i < local_dc_state->stream_count; i++) {
> > struct dc_stream_state *stream = dm_state->context-
> > > streams[i]; @@ -1316,9 +1323,9 @@ bool pre_validate_dsc(struct
> > drm_atomic_state *state,
> > if (ret != 0)
> > goto clean_exit;
> >
> > - if (!pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars)) {
> > + ret = pre_compute_mst_dsc_configs_for_state(state, local_dc_state,
> > vars);
> > + if (ret != 0) {
> >
> > DRM_INFO_ONCE("pre_compute_mst_dsc_configs_for_state()
> > failed\n");
> > - ret = -EINVAL;
> > goto clean_exit;
> > }
> >
> > @@ -1349,7 +1356,7 @@ bool pre_validate_dsc(struct drm_atomic_state
> > *state,
> >
> > kfree(local_dc_state);
> >
> > - return (ret == 0);
> > + return ret;
> > }
> >
> > static unsigned int kbps_from_pbn(unsigned int pbn) diff --git
> > a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > index b92a7c5671aa2..97fd70df531bf 100644
> > --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > +++
> > b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm_mst_types.h
> > @@ -53,15 +53,15 @@ struct dsc_mst_fairness_vars {
> > struct amdgpu_dm_connector *aconnector; };
> >
> > -bool compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > - struct dc_state *dc_state,
> > - struct dsc_mst_fairness_vars *vars);
> > +int compute_mst_dsc_configs_for_state(struct drm_atomic_state *state,
> > + struct dc_state *dc_state,
> > + struct dsc_mst_fairness_vars *vars);
> >
> > bool needs_dsc_aux_workaround(struct dc_link *link);
> >
> > -bool pre_validate_dsc(struct drm_atomic_state *state,
> > - struct dm_atomic_state **dm_state_ptr,
> > - struct dsc_mst_fairness_vars *vars);
> > +int pre_validate_dsc(struct drm_atomic_state *state,
> > + struct dm_atomic_state **dm_state_ptr,
> > + struct dsc_mst_fairness_vars *vars);
> >
> > enum dc_status dm_dp_mst_is_port_support_mode(
> > struct amdgpu_dm_connector *aconnector,
> > --
> > 2.37.3
> ---
> Regards,
> Wayne Lin
>

--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat


2022-11-14 22:17:44

by Lyude Paul

[permalink] [raw]
Subject: Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> >    }
> > - if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > + ret = drm_dp_mst_atomic_check(state);
> > + if (ret == 0 && !debugfs_overwrite) {
> >    set_dsc_configs_from_fairness_vars(params, vars, count,
> > k);
> > - return true;
> > + return 0;
> > + } else if (ret == -EDEADLK) {
> > + return ret;
>
> I think we should return here whenever there is an error. Not just for
> EDEADLK case.

Are we sure about this one? I think we may actually want to make this so it
returns on ret != -ENOSPC, since we want the function to continue if there's
no space in the atomic state available so it can try recomputing things with
compression enabled. On ret == 0 it should return early without doing
compression, and on ret == -ENOSPC it should just continue the function from
there

--
Cheers,
Lyude Paul (she/her)
Software Engineer at Red Hat


2022-11-16 05:06:55

by Lin, Wayne

[permalink] [raw]
Subject: RE: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and deadlocking

[Public]



> -----Original Message-----
> From: Lyude Paul <[email protected]>
> Sent: Tuesday, November 15, 2022 5:55 AM
> To: Lin, Wayne <[email protected]>; [email protected]
> Cc: Wentland, Harry <[email protected]>; [email protected];
> Li, Sun peng (Leo) <[email protected]>; Siqueira, Rodrigo
> <[email protected]>; Deucher, Alexander
> <[email protected]>; Koenig, Christian
> <[email protected]>; Pan, Xinhui <[email protected]>; David
> Airlie <[email protected]>; Daniel Vetter <[email protected]>; Kazlauskas,
> Nicholas <[email protected]>; Pillai, Aurabindo
> <[email protected]>; Li, Roman <[email protected]>; Zuo, Jerry
> <[email protected]>; Wu, Hersen <[email protected]>; Thomas
> Zimmermann <[email protected]>; Mahfooz, Hamza
> <[email protected]>; Hung, Alex <[email protected]>; Francis,
> David <[email protected]>; Mikita Lipski <[email protected]>; Liu,
> Wenjing <[email protected]>; open list:DRM DRIVERS <dri-
> [email protected]>; open list <[email protected]>
> Subject: Re: [PATCH 1/2] drm/amdgpu/mst: Stop ignoring error codes and
> deadlocking
>
> On Wed, 2022-11-09 at 09:48 +0000, Lin, Wayne wrote:
> > >    }
> > > - if (!drm_dp_mst_atomic_check(state) && !debugfs_overwrite) {
> > > + ret = drm_dp_mst_atomic_check(state);
> > > + if (ret == 0 && !debugfs_overwrite) {
> > >    set_dsc_configs_from_fairness_vars(params, vars, count, k);
> > > - return true;
> > > + return 0;
> > > + } else if (ret == -EDEADLK) {
> > > + return ret;
> >
> > I think we should return here whenever there is an error. Not just for
> > EDEADLK case.
>
> Are we sure about this one? I think we may actually want to make this so it
> returns on ret != -ENOSPC, since we want the function to continue if there's
> no space in the atomic state available so it can try recomputing things with
> compression enabled. On ret == 0 it should return early without doing
> compression, and on ret == -ENOSPC it should just continue the function
> from there
>
Oh, right.. Thanks for saving me from causing disaster : )

> --
> Cheers,
> Lyude Paul (she/her)
> Software Engineer at Red Hat
--
Regards,
Wayne