Re: Questions about KMS flip

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Am 16.11.21 um 09:00 schrieb Lang Yu:
On Tue, Nov 16, 2021 at 08:14:08AM +0100, Christian KKKnig wrote:
Am 16.11.21 um 04:27 schrieb Lang Yu:
On Mon, Nov 15, 2021 at 01:04:15PM +0100, Michel DDDnzer wrote:
[SNIP]
Though a single call to dce_v*_0_crtc_do_set_base() will
only pin the BO, I found it will be unpinned in next call to
dce_v*_0_crtc_do_set_base().
Yeah, that's the normal case when the new BO is different from the old one.

To catch the case I described, try something like

diff --git a/drivers/gpu/drm/amd/amdgpu/dce_v11_0.c b/drivers/gpu/drm/amd/amdgpu/dce_v11_0.c

index 18a7b3bd633b..5726bd87a355 100644

--- a/drivers/gpu/drm/amd/amdgpu/dce_v11_0.c

+++ b/drivers/gpu/drm/amd/amdgpu/dce_v11_0.c

@@ -1926,6 +1926,7 @@ static int dce_v11_0_crtc_do_set_base(struct drm_crtc *crtc,

                  return r;



          if (!atomic) {

+               WARN_ON_ONCE(target_fb == fb);

                  r = amdgpu_bo_pin(abo, AMDGPU_GEM_DOMAIN_VRAM);

                  if (unlikely(r != 0)) {

                          amdgpu_bo_unreserve(abo);

I did some tests, the warning can be triggered.

pin/unpin operations in *_crtc_do_set_base() and
amdgpu_display_crtc_page_flip_target() are mixed.
Ok sounds like we narrowed down the root cause pretty well.

Question is now how can we fix this? Just not pin the BO when target_fb ==
fb?
That worked. I did a few simple tests and didn't observe ttm_bo_release warnings
any more.

The pin/unpin logic,

1, fist crtc_mode_set, dce_v*_0_crtc_do_set_base() pins crtc->primary->fb(new),
old_fb is NULL.

2, second crtc_mode_set, dce_v*_0_crtc_do_set_base() pins crtc->primary->fb(new),
unpins old fb.

3, amdgpu_display_crtc_page_flip_target() pin/unpin operations.

4, third crtc_mode_set, dce_v*_0_crtc_do_set_base() pins crtc->primary->fb(new),
unpins old fb (it is pinned in last call to amdgpu_display_crtc_page_flip_target)

5, amdgpu_display_crtc_page_flip_target() pin/unpin operations.

.....

x, reboot, amdgpu_display_suspend_helper() is called, the last pinned fb was unpinned.

And I didn't observe amdgpu_bo_unpin() in dce_v*_0_crtc_disable() is called.

If the logic is wrong, please correct me.

I can't fully judge because I'm not that deep with my head in the old display code, but from a ten mile high view it sounds sane to me. Michel what do you think?

BTW: Nicholas are there any plans to get rid of all that stuff? It would be a really nice cleanup of rather flaky code I think.

Thanks,
Christian.


Regards,
Lang

Thanks,
Christian.

Regards,
Lang





[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux