On 09/05/2025 06:08, Jun Nie wrote:
Dmitry Baryshkov <dmitry.barysh...@oss.qualcomm.com> 于2025年5月8日周四 18:47写道：
On Tue, May 06, 2025 at 11:47:31PM +0800, Jun Nie wrote:
Some display controller support flexible CRTC and DMA, such as the display
controllers in snapdragon SoCs. CRTC can be implemented with several mixers
in parallel, and plane fetching can be implemented with several DMA under
umberala of a virtual drm plane.
The mixer number is decided per panel resolution and clock rate constrain
first, which happens in CRTC side. Then plane is split per mixer number
and configure DMA accordingly.
Here you are describing a behaviour of one particular driver as a reason
to change the framework.
Yeah, the specific driver requires a change in framework. Maybe the
comment is not
proper?
Yes. Explain how does that benefit the framework / other drivers.
Otherwise the answer would be as simple as 'replace
drm_atomic_helper_check_planes() in your driver'.
To support such forthcoming usage case, CRTC checking shall happen before
checking plane. Add the checking in the drm_atomic_helper_check_modeset().
So, now drivers will get two calls to atomic_check(), one coming in
circumstances which were not expected by the drivers before. Are you
sure that this won't break anything?
Yes, it is a concern. Is there any way to limit the change in
framework to specific
driver with a flag, such as DRM_FLAG_CHECK_CRTC_BEFORE_PLANE?
Definitely not with a flag. You can try adding a new helper callback,
but I don't know how DRM core maintainers would react to it.
Signed-off-by: Jun Nie <jun....@linaro.org>
---
drivers/gpu/drm/drm_atomic_helper.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/drivers/gpu/drm/drm_atomic_helper.c
b/drivers/gpu/drm/drm_atomic_helper.c
index
5302ab3248985d3e0a47e40fd3deb7ad0d9f775b..5bca4c9683838c38574c8cb7c0bc9d57960314fe
100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -816,6 +816,25 @@ drm_atomic_helper_check_modeset(struct drm_device *dev,
return ret;
}
+ for_each_new_crtc_in_state(state, crtc, new_crtc_state, i) {
+ const struct drm_crtc_helper_funcs *funcs;
+
+ funcs = crtc->helper_private;
+
+ if (!funcs || !funcs->atomic_check)
+ continue;
+
+ ret = funcs->atomic_check(crtc, state);
+ if (ret) {
+ drm_dbg_atomic(crtc->dev,
+ "[CRTC:%d:%s] atomic driver check
failed\n",
+ crtc->base.id, crtc->name);
+ return ret;
+ }
+ }
+
+
+
Too many empty lines. But the main quesiton is: why are you calling it
before mode_valid()? According to your description a better place would
be in drm_atomic_helper_check_planes().
Agree, that's the proper function. Will remove the empty line in next version.
ret = mode_valid(state);
if (ret)
return ret;
--
2.34.1
--
With best wishes
Dmitry
--
With best wishes
Dmitry
