On Wed, Dec 5, 2012 at 5:33 PM, Eunchul Kim chulspro.kim@samsung.comwrote:
Dear Prathyush
Thank's your clarification.
I have one opinion about your [PATCH 1/3] How about to add atomic_read() condition in each irq_handler ? like this.
e.g)
Hi Eunchul,
Yes, I think this is better. I'll modify this in the next patch version and post tomorrow.
Thanks for reviewing.
Regards, Prathyush
if (atomic_read(&ctx->wait_vsync_**event)) {/* set wait vsync event to zero and wake up queue. */atomic_set(&ctx->wait_vsync_**event, 0);DRM_WAKEUP(&ctx->wait_vsync_**queue);}I lost your PATCH mail. so, I send my comment using this body mail.
Thank's BR
Eunchul Kim.
On 12/05/2012 04:27 PM, Inki Dae wrote:
2012/12/5 Inki Dae inki.dae@samsung.com
2012/12/5 Inki Dae inki.dae@samsung.com
2012/12/5 Prathyush K prathyush@chromium.org
On Wed, Dec 5, 2012 at 11:40 AM, Inki Dae inki.dae@samsung.com wrote:
2012/12/5 Inki Dae inki.dae@samsung.com
> > 2012/12/5 Prathyush K prathyush.k@samsung.com > > This patchset fixes a few issues with use of wait for vblank in >> exynos drm. >> >> Please apply these three patches without "drm/exynos: release fb >> pended by page flip" >> patch. >> >> Patch 1: modify wait for vsync functions to use wait queues >> This modifies the wait_for_vblank functions to use wait queues >> thus ensuring that the current task goes to sleep without taking >> up CPU while waiting. >> >> Patch 2: move wait_for_vblank to manager_ops >> Currently, we do not call wait for vblank if encoder is in DPMS_OFF >> state inside exynos_drm_encoder_complete_**scanout function. This >> is >> because wait for vblank is treated as an overlay op. >> > > This can be > >> modified to a manager_op thus removing the above check for DPMS_OFF. >> This fixes a crash while removing a fb. >> While removing the current fb (crtc->fb == fb) the encoder >> dpms off is called and then the framebuffer is removed. So in >> this case, the wait for vblank is not called thus leading to a crash >> (since fb might get removed before dma is finished) >> >> Patch 3: do not disable crtc if already off >> We should not disable the overlay if the crtc is in DPMS_OFF state. >> Also, the disable function should not call DPMS_OFF of the crtc. >> This is required to ensure we are able to wait for vblank >> before freeing any framebuffers after disabling the crtc. >> >> With these three patches and without "drm/exynos: release fb pended >> by page flip" >> I could not find any crash/page_fault in drm with fimd/hdmi during >> hotplug >> and page flips. >> >> >> It seems better than old one and also including some exception > codes, > Patch 3 we did't consider. Ok, we will test these patches and merge > them > instead of old one if no problem. > > > Tested and worked fine. But with this patch and without "drm/exynos: release fb pended by page flip", we would still have potential issue to page fault like below,
- dma is accessing no current fb
- the fb to be released is not current fb so the fb would be released
without disabling crtc when drm is released. 3. but the memory region to no current fb is being accessed by the dma so the page fault would be induced. This is a rare case but possible issue.
Hi Mr. Dae,
But we would not release the fb till we get a vblank (i.e. wait for vblank is called before removing every framebuffer).
Taking your example itself:
fb0 is current fb i.e. (crtc->fb = fb0).
But the dma is accessing from fb1.
We call remove fb1.
In this case, as you said, crtc will not be disabled as fb1 is not current fb.
But we wait for vblank before removing fb1. Thus we ensure that dma from fb1 is complete and dma from fb0 has started. So it is safe to remove fb1.
Please, see the below codes,
drm_release() drm_fb_release() drm_framebuffer_remove() /* assume that current fb is fb1 and dma is accessing fb0 but trying to release fb0 at here */ /* this situation could be reproduced with pageflip test. */ fb0 is not crtc->fb so the crtc isn't disabled ... drm_framebuffer_unreference(**fb0); <- fb0 will be released without wait_for_vblank().
The wait_for_vblank() is called by exynos_drm_encoder_complete_** scanout() when fb->func->destroy() is called so the wait_for_vblank() will be called after fb0 is released. Is there another place that wait_for_vblank() is called?
Ah, sorry~. exynos_drm_encoder_**completescanout() is called prior to
gem releasing. Right, no problem. :)
Thanks, Inki Dae
In addition,
I had added exynos_drm_encoder_complete_**scanout() function to resolve this issue. but it seems like that previous patch didn't perform wait_for_vblank correctly. Anyway this is just exynos specific code. so I hope maybe Daniel's fixup can resolve this issue in drm core.
Thanks, Inki Dae
Thanks,
Inki Dae
Hope I correctly understood the issue you mentioned.
Anyway I removed the patch, "drm/exynos: release fb pended by page
flip". And I hope this issue can be resolved by Daniel's fixup later.
And I think it's better to separate your patch set into 4 patches like below,
- the patch including only exynos drm framework part.
- the patch including only fimd driver part.
- the patch including only hdmi driver part.
- the patch including exception code.(previous Patch 3)
Please, re-send them.
Sure. I'll post them again as requested.
Regards, Prathyush
Thanks,
Inki Dae
Thanks,
> Inki Dae > > > Prathyush K (3) >> drm/exynos: modify wait for vsync functions to use wait queues >> drm/exynos: move wait_for_vblank to manager_ops >> drm/exynos: do not disable crtc if already off >> >> drivers/gpu/drm/exynos/exynos_**drm_crtc.c | 6 +++- >> drivers/gpu/drm/exynos/exynos_**drm_drv.h | 20 >> ++------------ >> drivers/gpu/drm/exynos/exynos_**drm_encoder.c | 15 +++-------- >> drivers/gpu/drm/exynos/exynos_**drm_fimd.c | 37 >> ++++++++++++++++++-------- >> drivers/gpu/drm/exynos/exynos_**drm_hdmi.c | 22 >> ++++++++-------- >> drivers/gpu/drm/exynos/exynos_**drm_hdmi.h | 2 +- >> drivers/gpu/drm/exynos/exynos_**mixer.c | 37 >> +++++++++++++++++--------- >> 7 files changed, 73 insertions(+), 66 deletions(-) >> >> ______________________________**_________________ >> dri-devel mailing list >> dri-devel@lists.freedesktop.**org dri-devel@lists.freedesktop.org >> http://lists.freedesktop.org/**mailman/listinfo/dri-develhttp://lists.freedesktop.org/mailman/listinfo/dri-devel >> >> > > ______________________________**_________________ dri-devel mailing list dri-devel@lists.freedesktop.**org dri-devel@lists.freedesktop.org http://lists.freedesktop.org/**mailman/listinfo/dri-develhttp://lists.freedesktop.org/mailman/listinfo/dri-devel
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