2020-04-24 19:09:37

by Lyude Paul

Subject: [PATCH] drm/dp_mst: Fix drm_dp_send_dpcd_write() return code

drm_dp_mst_wait_tx_reply() returns > 1 if time elapsed in
wait_event_timeout() before check_txmsg_state(mgr, txmsg) evaluated to
true. However, we make the mistake of returning this time from
drm_dp_send_dpcd_write() on success instead of returning the number of
bytes written - causing spontaneous failures during link probing:

[drm:drm_dp_send_link_address [drm_kms_helper]] *ERROR* GUID check on
10:01 failed: 3975

Yikes! So, fix this by returning the number of bytes written on success
instead.

Signed-off-by: Lyude Paul <[email protected]>
Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
Cc: Benjamin Gaignard <[email protected]>
Cc: Sean Paul <[email protected]>
---
drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
index 03a1496f6120..21dc78cb4ba6 100644
--- a/drivers/gpu/drm/drm_dp_mst_topology.c
+++ b/drivers/gpu/drm/drm_dp_mst_topology.c
@@ -3436,8 +3436,12 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
drm_dp_queue_down_tx(mgr, txmsg);

ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
- if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
- ret = -EIO;
+ if (ret > 0) {
+ if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
+ ret = -EIO;
+ else
+ ret = size;
+ }

kfree(txmsg);
fail_put:
--
2.25.3

2020-04-24 19:18:46

by Alex Deucher

Subject: Re: [PATCH] drm/dp_mst: Fix drm_dp_send_dpcd_write() return code

On Fri, Apr 24, 2020 at 3:07 PM Lyude Paul <[email protected]> wrote:
>
> drm_dp_mst_wait_tx_reply() returns > 1 if time elapsed in
> wait_event_timeout() before check_txmsg_state(mgr, txmsg) evaluated to
> true. However, we make the mistake of returning this time from
> drm_dp_send_dpcd_write() on success instead of returning the number of
> bytes written - causing spontaneous failures during link probing:
>
> [drm:drm_dp_send_link_address [drm_kms_helper]] *ERROR* GUID check on
> 10:01 failed: 3975
>
> Yikes! So, fix this by returning the number of bytes written on success
> instead.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
> Cc: Benjamin Gaignard <[email protected]>
> Cc: Sean Paul <[email protected]>

Acked-by: Alex Deucher <[email protected]>

> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 03a1496f6120..21dc78cb4ba6 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3436,8 +3436,12 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
> drm_dp_queue_down_tx(mgr, txmsg);
>
> ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
> - if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
> - ret = -EIO;
> + if (ret > 0) {
> + if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
> + ret = -EIO;
> + else
> + ret = size;
> + }
>
> kfree(txmsg);
> fail_put:
> --
> 2.25.3
>
> _______________________________________________
> dri-devel mailing list
> [email protected]
> https://lists.freedesktop.org/mailman/listinfo/dri-devel

2020-04-27 14:00:40

by Sean Paul

Subject: Re: [PATCH] drm/dp_mst: Fix drm_dp_send_dpcd_write() return code

On Fri, Apr 24, 2020 at 3:07 PM Lyude Paul <[email protected]> wrote:
>
> drm_dp_mst_wait_tx_reply() returns > 1 if time elapsed in
> wait_event_timeout() before check_txmsg_state(mgr, txmsg) evaluated to
> true. However, we make the mistake of returning this time from
> drm_dp_send_dpcd_write() on success instead of returning the number of
> bytes written - causing spontaneous failures during link probing:
>
> [drm:drm_dp_send_link_address [drm_kms_helper]] *ERROR* GUID check on
> 10:01 failed: 3975
>
> Yikes! So, fix this by returning the number of bytes written on success
> instead.
>
> Signed-off-by: Lyude Paul <[email protected]>
> Fixes: cb897542c6d2 ("drm/dp_mst: Fix W=1 warnings")
> Cc: Benjamin Gaignard <[email protected]>
> Cc: Sean Paul <[email protected]>

Reviewed-by: Sean Paul <[email protected]>

> ---
> drivers/gpu/drm/drm_dp_mst_topology.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 03a1496f6120..21dc78cb4ba6 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -3436,8 +3436,12 @@ static int drm_dp_send_dpcd_write(struct drm_dp_mst_topology_mgr *mgr,
> drm_dp_queue_down_tx(mgr, txmsg);
>
> ret = drm_dp_mst_wait_tx_reply(mstb, txmsg);
> - if (ret > 0 && txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
> - ret = -EIO;
> + if (ret > 0) {
> + if (txmsg->reply.reply_type == DP_SIDEBAND_REPLY_NAK)
> + ret = -EIO;
> + else
> + ret = size;
> + }
>
> kfree(txmsg);
> fail_put:
> --
> 2.25.3
>