Hi,
This work from me and Simon adds support for DRM_MODE_PAGE_FLIP_ASYNC through
the atomic API. This feature is already available via the legacy API. The use
case is to be able to present a new frame immediately (or as soon as
possible), even if after missing a vblank. This might result in tearing, but
it's useful when a high framerate is desired, such as for gaming.
Differently from earlier versions, this one refuses to flip if any prop changes
for async flips. The idea is that the fast path of immediate page flips doesn't
play well with modeset changes, so only the fb_id can be changed.
Tested with:
- Intel TigerLake-LP GT2
- AMD VanGogh
Thanks,
André
- User-space patch: https://github.com/Plagman/gamescope/pull/595
- IGT tests: https://lore.kernel.org/all/[email protected]/
Changes from v8:
- Dropped atomic_async_page_flip_not_supported, giving that current design works
with any driver that support atomic and async at the same time.
- Dropped the patch that disabled atomic_async_page_flip_not_supported for AMD.
- Reordered commits
v8: https://lore.kernel.org/all/[email protected]/
Changes from v7:
- Only accept flips to primary planes. If a driver support flips in different
planes, support will be added later.
v7: https://lore.kernel.org/dri-devel/[email protected]/
Changes from v6:
- Dropped the exception to allow MODE_ID changes (Simon)
- Clarify what happens when flipping with the same FB_ID (Pekka)
v6: https://lore.kernel.org/dri-devel/[email protected]/
Changes from v5:
- Add note in the docs that not every redundant attribute will result in no-op,
some might cause oversynchronization issues.
v5: https://lore.kernel.org/dri-devel/[email protected]/
Changes from v4:
- Documentation rewrote by Pekka Paalanen
v4: https://lore.kernel.org/dri-devel/[email protected]/
Changes from v3:
- Add new patch to reject prop changes
- Add a documentation clarifying the KMS atomic state set
v3: https://lore.kernel.org/dri-devel/[email protected]/
André Almeida (1):
drm: Refuse to async flip with atomic prop changes
Pekka Paalanen (1):
drm/doc: Define KMS atomic state set
Simon Ser (2):
drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
drm: introduce DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP
Documentation/gpu/drm-uapi.rst | 47 ++++++++++++++++++
drivers/gpu/drm/drm_atomic_uapi.c | 77 ++++++++++++++++++++++++++---
drivers/gpu/drm/drm_crtc_internal.h | 2 +-
drivers/gpu/drm/drm_ioctl.c | 4 ++
drivers/gpu/drm/drm_mode_object.c | 2 +-
include/uapi/drm/drm.h | 10 +++-
include/uapi/drm/drm_mode.h | 9 ++++
7 files changed, 142 insertions(+), 9 deletions(-)
--
2.42.1
Given that prop changes may lead to modesetting, which would defeat the
fast path of the async flip, refuse any atomic prop change for async
flips in atomic API. The only exception is the framebuffer ID to flip
to. Currently the only plane type supported is the primary one.
Signed-off-by: André Almeida <[email protected]>
Reviewed-by: Simon Ser <[email protected]>
---
v9: no changes
v8: add a check for plane type, we can only flip primary planes
v7: drop the mode_id exception for prop changes
---
drivers/gpu/drm/drm_atomic_uapi.c | 52 +++++++++++++++++++++++++++--
drivers/gpu/drm/drm_crtc_internal.h | 2 +-
drivers/gpu/drm/drm_mode_object.c | 2 +-
3 files changed, 51 insertions(+), 5 deletions(-)
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index 98d3b10c08ae..ed46133a2dd7 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1006,13 +1006,28 @@ int drm_atomic_connector_commit_dpms(struct drm_atomic_state *state,
return ret;
}
+static int drm_atomic_check_prop_changes(int ret, uint64_t old_val, uint64_t prop_value,
+ struct drm_property *prop)
+{
+ if (ret != 0 || old_val != prop_value) {
+ drm_dbg_atomic(prop->dev,
+ "[PROP:%d:%s] No prop can be changed during async flip\n",
+ prop->base.id, prop->name);
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
int drm_atomic_set_property(struct drm_atomic_state *state,
struct drm_file *file_priv,
struct drm_mode_object *obj,
struct drm_property *prop,
- uint64_t prop_value)
+ uint64_t prop_value,
+ bool async_flip)
{
struct drm_mode_object *ref;
+ uint64_t old_val;
int ret;
if (!drm_property_change_valid_get(prop, prop_value, &ref))
@@ -1029,6 +1044,13 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
break;
}
+ if (async_flip) {
+ ret = drm_atomic_connector_get_property(connector, connector_state,
+ prop, &old_val);
+ ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
+ break;
+ }
+
ret = drm_atomic_connector_set_property(connector,
connector_state, file_priv,
prop, prop_value);
@@ -1044,6 +1066,13 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
break;
}
+ if (async_flip) {
+ ret = drm_atomic_crtc_get_property(crtc, crtc_state,
+ prop, &old_val);
+ ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
+ break;
+ }
+
ret = drm_atomic_crtc_set_property(crtc,
crtc_state, prop, prop_value);
break;
@@ -1051,6 +1080,7 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
case DRM_MODE_OBJECT_PLANE: {
struct drm_plane *plane = obj_to_plane(obj);
struct drm_plane_state *plane_state;
+ struct drm_mode_config *config = &plane->dev->mode_config;
plane_state = drm_atomic_get_plane_state(state, plane);
if (IS_ERR(plane_state)) {
@@ -1058,6 +1088,21 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
break;
}
+ if (async_flip && prop != config->prop_fb_id) {
+ ret = drm_atomic_plane_get_property(plane, plane_state,
+ prop, &old_val);
+ ret = drm_atomic_check_prop_changes(ret, old_val, prop_value, prop);
+ break;
+ }
+
+ if (async_flip && plane_state->plane->type != DRM_PLANE_TYPE_PRIMARY) {
+ drm_dbg_atomic(prop->dev,
+ "[OBJECT:%d] Only primary planes can be changed during async flip\n",
+ obj->id);
+ ret = -EINVAL;
+ break;
+ }
+
ret = drm_atomic_plane_set_property(plane,
plane_state, file_priv,
prop, prop_value);
@@ -1337,6 +1382,7 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
struct drm_out_fence_state *fence_state;
int ret = 0;
unsigned int i, j, num_fences;
+ bool async_flip = false;
/* disallow for drivers not supporting atomic: */
if (!drm_core_check_feature(dev, DRIVER_ATOMIC))
@@ -1450,8 +1496,8 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
goto out;
}
- ret = drm_atomic_set_property(state, file_priv,
- obj, prop, prop_value);
+ ret = drm_atomic_set_property(state, file_priv, obj,
+ prop, prop_value, async_flip);
if (ret) {
drm_mode_object_put(obj);
goto out;
diff --git a/drivers/gpu/drm/drm_crtc_internal.h b/drivers/gpu/drm/drm_crtc_internal.h
index 6b646e0783be..c05c9ee9c859 100644
--- a/drivers/gpu/drm/drm_crtc_internal.h
+++ b/drivers/gpu/drm/drm_crtc_internal.h
@@ -253,7 +253,7 @@ int drm_atomic_set_property(struct drm_atomic_state *state,
struct drm_file *file_priv,
struct drm_mode_object *obj,
struct drm_property *prop,
- uint64_t prop_value);
+ uint64_t prop_value, bool async_flip);
int drm_atomic_get_property(struct drm_mode_object *obj,
struct drm_property *property, uint64_t *val);
diff --git a/drivers/gpu/drm/drm_mode_object.c b/drivers/gpu/drm/drm_mode_object.c
index ac0d2ce3f870..0e8355063eee 100644
--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -538,7 +538,7 @@ static int set_property_atomic(struct drm_mode_object *obj,
obj_to_connector(obj),
prop_value);
} else {
- ret = drm_atomic_set_property(state, file_priv, obj, prop, prop_value);
+ ret = drm_atomic_set_property(state, file_priv, obj, prop, prop_value, false);
if (ret)
goto out;
ret = drm_atomic_commit(state);
--
2.42.1
From: Simon Ser <[email protected]>
If the driver supports it, allow user-space to supply the
DRM_MODE_PAGE_FLIP_ASYNC flag to request an async page-flip.
Set drm_crtc_state.async_flip accordingly.
Document that drivers will reject atomic commits if an async
flip isn't possible. This allows user-space to fall back to
something else. For instance, Xorg falls back to a blit.
Another option is to wait as close to the next vblank as
possible before performing the page-flip to reduce latency.
Signed-off-by: Simon Ser <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Co-developed-by: André Almeida <[email protected]>
Signed-off-by: André Almeida <[email protected]>
---
v9: dropped atomic_async_page_flip_not_supported
---
drivers/gpu/drm/drm_atomic_uapi.c | 25 ++++++++++++++++++++++---
include/uapi/drm/drm_mode.h | 9 +++++++++
2 files changed, 31 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c
index ed46133a2dd7..de4265423ddc 100644
--- a/drivers/gpu/drm/drm_atomic_uapi.c
+++ b/drivers/gpu/drm/drm_atomic_uapi.c
@@ -1368,6 +1368,18 @@ static void complete_signaling(struct drm_device *dev,
kfree(fence_state);
}
+static void
+set_async_flip(struct drm_atomic_state *state)
+{
+ struct drm_crtc *crtc;
+ struct drm_crtc_state *crtc_state;
+ int i;
+
+ for_each_new_crtc_in_state(state, crtc, crtc_state, i) {
+ crtc_state->async_flip = true;
+ }
+}
+
int drm_mode_atomic_ioctl(struct drm_device *dev,
void *data, struct drm_file *file_priv)
{
@@ -1409,9 +1421,13 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
}
if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC) {
- drm_dbg_atomic(dev,
- "commit failed: invalid flag DRM_MODE_PAGE_FLIP_ASYNC\n");
- return -EINVAL;
+ if (!dev->mode_config.async_page_flip) {
+ drm_dbg_atomic(dev,
+ "commit failed: DRM_MODE_PAGE_FLIP_ASYNC not supported\n");
+ return -EINVAL;
+ }
+
+ async_flip = true;
}
/* can't test and expect an event at the same time. */
@@ -1514,6 +1530,9 @@ int drm_mode_atomic_ioctl(struct drm_device *dev,
if (ret)
goto out;
+ if (arg->flags & DRM_MODE_PAGE_FLIP_ASYNC)
+ set_async_flip(state);
+
if (arg->flags & DRM_MODE_ATOMIC_TEST_ONLY) {
ret = drm_atomic_check_only(state);
} else if (arg->flags & DRM_MODE_ATOMIC_NONBLOCK) {
diff --git a/include/uapi/drm/drm_mode.h b/include/uapi/drm/drm_mode.h
index 09e7a471ee30..95630f170110 100644
--- a/include/uapi/drm/drm_mode.h
+++ b/include/uapi/drm/drm_mode.h
@@ -957,6 +957,15 @@ struct hdr_output_metadata {
* Request that the page-flip is performed as soon as possible, ie. with no
* delay due to waiting for vblank. This may cause tearing to be visible on
* the screen.
+ *
+ * When used with atomic uAPI, the driver will return an error if the hardware
+ * doesn't support performing an asynchronous page-flip for this update.
+ * User-space should handle this, e.g. by falling back to a regular page-flip.
+ *
+ * Note, some hardware might need to perform one last synchronous page-flip
+ * before being able to switch to asynchronous page-flips. As an exception,
+ * the driver will return success even though that first page-flip is not
+ * asynchronous.
*/
#define DRM_MODE_PAGE_FLIP_ASYNC 0x02
#define DRM_MODE_PAGE_FLIP_TARGET_ABSOLUTE 0x4
--
2.42.1
From: Simon Ser <[email protected]>
This new kernel capability indicates whether async page-flips are
supported via the atomic uAPI. DRM clients can use it to check
for support before feeding DRM_MODE_PAGE_FLIP_ASYNC to the kernel.
Make it clear that DRM_CAP_ASYNC_PAGE_FLIP is for legacy uAPI only.
Signed-off-by: Simon Ser <[email protected]>
Reviewed-by: André Almeida <[email protected]>
Reviewed-by: Alex Deucher <[email protected]>
Signed-off-by: André Almeida <[email protected]>
---
v9: no changes
---
---
drivers/gpu/drm/drm_ioctl.c | 4 ++++
include/uapi/drm/drm.h | 10 +++++++++-
2 files changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_ioctl.c b/drivers/gpu/drm/drm_ioctl.c
index 44fda68c28ae..f461ed862480 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -301,6 +301,10 @@ static int drm_getcap(struct drm_device *dev, void *data, struct drm_file *file_
case DRM_CAP_CRTC_IN_VBLANK_EVENT:
req->value = 1;
break;
+ case DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP:
+ req->value = drm_core_check_feature(dev, DRIVER_ATOMIC) &&
+ dev->mode_config.async_page_flip;
+ break;
default:
return -EINVAL;
}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 8662b5aeea0c..796de831f4a0 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -713,7 +713,8 @@ struct drm_gem_open {
/**
* DRM_CAP_ASYNC_PAGE_FLIP
*
- * If set to 1, the driver supports &DRM_MODE_PAGE_FLIP_ASYNC.
+ * If set to 1, the driver supports &DRM_MODE_PAGE_FLIP_ASYNC for legacy
+ * page-flips.
*/
#define DRM_CAP_ASYNC_PAGE_FLIP 0x7
/**
@@ -773,6 +774,13 @@ struct drm_gem_open {
* :ref:`drm_sync_objects`.
*/
#define DRM_CAP_SYNCOBJ_TIMELINE 0x14
+/**
+ * DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP
+ *
+ * If set to 1, the driver supports &DRM_MODE_PAGE_FLIP_ASYNC for atomic
+ * commits.
+ */
+#define DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP 0x15
/* DRM_IOCTL_GET_CAP ioctl argument type */
struct drm_get_cap {
--
2.42.1
From: Pekka Paalanen <[email protected]>
Specify how the atomic state is maintained between userspace and
kernel, plus the special case for async flips.
Signed-off-by: Pekka Paalanen <[email protected]>
Signed-off-by: André Almeida <[email protected]>
---
v9:
- no changes
v8:
- no changes
v7:
- add a note that drivers can make exceptions for ad-hoc prop changes
- add a note about flipping the same FB_ID as a no-op
---
---
Documentation/gpu/drm-uapi.rst | 47 ++++++++++++++++++++++++++++++++++
1 file changed, 47 insertions(+)
diff --git a/Documentation/gpu/drm-uapi.rst b/Documentation/gpu/drm-uapi.rst
index 370d820be248..d0693f902a5c 100644
--- a/Documentation/gpu/drm-uapi.rst
+++ b/Documentation/gpu/drm-uapi.rst
@@ -570,3 +570,50 @@ dma-buf interoperability
Please see Documentation/userspace-api/dma-buf-alloc-exchange.rst for
information on how dma-buf is integrated and exposed within DRM.
+
+KMS atomic state
+================
+
+An atomic commit can change multiple KMS properties in an atomic fashion,
+without ever applying intermediate or partial state changes. Either the whole
+commit succeeds or fails, and it will never be applied partially. This is the
+fundamental improvement of the atomic API over the older non-atomic API which is
+referred to as the "legacy API". Applying intermediate state could unexpectedly
+fail, cause visible glitches, or delay reaching the final state.
+
+An atomic commit can be flagged with DRM_MODE_ATOMIC_TEST_ONLY, which means the
+complete state change is validated but not applied. Userspace should use this
+flag to validate any state change before asking to apply it. If validation fails
+for any reason, userspace should attempt to fall back to another, perhaps
+simpler, final state. This allows userspace to probe for various configurations
+without causing visible glitches on screen and without the need to undo a
+probing change.
+
+The changes recorded in an atomic commit apply on top the current KMS state in
+the kernel. Hence, the complete new KMS state is the complete old KMS state with
+the committed property settings done on top. The kernel will try to avoid
+no-operation changes, so it is safe for userspace to send redundant property
+settings. However, not every situation allows for no-op changes, due to the
+need to acquire locks for some attributes. Userspace needs to be aware that some
+redundant information might result in oversynchronization issues. No-operation
+changes do not count towards actually needed changes, e.g. setting MODE_ID to a
+different blob with identical contents as the current KMS state shall not be a
+modeset on its own. As a special exception for VRR needs, explicitly setting
+FB_ID to its current value is not a no-op.
+
+A "modeset" is a change in KMS state that might enable, disable, or temporarily
+disrupt the emitted video signal, possibly causing visible glitches on screen. A
+modeset may also take considerably more time to complete than other kinds of
+changes, and the video sink might also need time to adapt to the new signal
+properties. Therefore a modeset must be explicitly allowed with the flag
+DRM_MODE_ATOMIC_ALLOW_MODESET. This in combination with
+DRM_MODE_ATOMIC_TEST_ONLY allows userspace to determine if a state change is
+likely to cause visible disruption on screen and avoid such changes when end
+users do not expect them.
+
+An atomic commit with the flag DRM_MODE_PAGE_FLIP_ASYNC is allowed to
+effectively change only the FB_ID property on any planes. No-operation changes
+are ignored as always. Changing any other property will cause the commit to be
+rejected. Each driver may relax this restriction if they have guarantees that
+such property change doesn't cause modesets. Userspace can use TEST_ONLY commits
+to query the driver about this.
--
2.42.1
Hi André,
On 11/22/23 11:19, André Almeida wrote:
> Hi,
>
> This work from me and Simon adds support for DRM_MODE_PAGE_FLIP_ASYNC through
> the atomic API. This feature is already available via the legacy API. The use
> case is to be able to present a new frame immediately (or as soon as
> possible), even if after missing a vblank. This might result in tearing, but
> it's useful when a high framerate is desired, such as for gaming.
>
> Differently from earlier versions, this one refuses to flip if any prop changes
> for async flips. The idea is that the fast path of immediate page flips doesn't
> play well with modeset changes, so only the fb_id can be changed.
>
> Tested with:
> - Intel TigerLake-LP GT2
> - AMD VanGogh
Have you had a chance to test this with VRR enabled? Since, I suspect
this series might break that feature.
>
> Thanks,
> André
>
> - User-space patch: https://github.com/Plagman/gamescope/pull/595
> - IGT tests: https://lore.kernel.org/all/[email protected]/
>
> Changes from v8:
> - Dropped atomic_async_page_flip_not_supported, giving that current design works
> with any driver that support atomic and async at the same time.
> - Dropped the patch that disabled atomic_async_page_flip_not_supported for AMD.
> - Reordered commits
> v8: https://lore.kernel.org/all/[email protected]/
>
> Changes from v7:
> - Only accept flips to primary planes. If a driver support flips in different
> planes, support will be added later.
> v7: https://lore.kernel.org/dri-devel/[email protected]/
>
> Changes from v6:
> - Dropped the exception to allow MODE_ID changes (Simon)
> - Clarify what happens when flipping with the same FB_ID (Pekka)
>
> v6: https://lore.kernel.org/dri-devel/[email protected]/
>
> Changes from v5:
> - Add note in the docs that not every redundant attribute will result in no-op,
> some might cause oversynchronization issues.
>
> v5: https://lore.kernel.org/dri-devel/[email protected]/
>
> Changes from v4:
> - Documentation rewrote by Pekka Paalanen
>
> v4: https://lore.kernel.org/dri-devel/[email protected]/
>
> Changes from v3:
> - Add new patch to reject prop changes
> - Add a documentation clarifying the KMS atomic state set
>
> v3: https://lore.kernel.org/dri-devel/[email protected]/
>
> André Almeida (1):
> drm: Refuse to async flip with atomic prop changes
>
> Pekka Paalanen (1):
> drm/doc: Define KMS atomic state set
>
> Simon Ser (2):
> drm: allow DRM_MODE_PAGE_FLIP_ASYNC for atomic commits
> drm: introduce DRM_CAP_ATOMIC_ASYNC_PAGE_FLIP
>
> Documentation/gpu/drm-uapi.rst | 47 ++++++++++++++++++
> drivers/gpu/drm/drm_atomic_uapi.c | 77 ++++++++++++++++++++++++++---
> drivers/gpu/drm/drm_crtc_internal.h | 2 +-
> drivers/gpu/drm/drm_ioctl.c | 4 ++
> drivers/gpu/drm/drm_mode_object.c | 2 +-
> include/uapi/drm/drm.h | 10 +++-
> include/uapi/drm/drm_mode.h | 9 ++++
> 7 files changed, 142 insertions(+), 9 deletions(-)
>
--
Hamza
Hi Hamza,
Em 22/11/2023 17:23, Hamza Mahfooz escreveu:
> Hi André,
> On 11/22/23 11:19, André Almeida wrote:
>> Hi,
>>
>> This work from me and Simon adds support for DRM_MODE_PAGE_FLIP_ASYNC
>> through
>> the atomic API. This feature is already available via the legacy API.
>> The use
>> case is to be able to present a new frame immediately (or as soon as
>> possible), even if after missing a vblank. This might result in
>> tearing, but
>> it's useful when a high framerate is desired, such as for gaming.
>>
>> Differently from earlier versions, this one refuses to flip if any
>> prop changes
>> for async flips. The idea is that the fast path of immediate page
>> flips doesn't
>> play well with modeset changes, so only the fb_id can be changed.
>>
>> Tested with:
>> - Intel TigerLake-LP GT2
>> - AMD VanGogh
>
> Have you had a chance to test this with VRR enabled? Since, I suspect
> this series might break that feature.
>
Someone asked this question in an earlier version of this patch, and the
result is that VRR still works as expected. You can follow the thread at
this link:
https://lore.kernel.org/lkml/[email protected]/
I should have included this note at my cover letter, my bad.
Thanks,
André
Thanks! This iteration of the first 3 patches LGTM, I've pushed them to
drm-misc-next. I've made two adjustments to make checkpatch.pl happy:
- s/uint64_t/u64/
- Fix indentation for a drm_dbg_atomic()
Em 23/11/2023 13:24, Simon Ser escreveu:
> Thanks! This iteration of the first 3 patches LGTM, I've pushed them to
> drm-misc-next. I've made two adjustments to make checkpatch.pl happy:
>
Thank you!
> - s/uint64_t/u64/
> - Fix indentation for a drm_dbg_atomic()
ops :)