Re: [PATCH 1/2] drm/rockchip: vop: Do check if an update is pending during disable
From: Mark yao
Date: Mon May 23 2016 - 02:36:27 EST
On 2016å05æ05æ 17:34, Tomeu Vizoso wrote:
On 20 April 2016 at 16:23, Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx> wrote:
On 11 April 2016 at 03:15, Mark yao <mark.yao@xxxxxxxxxxxxxx> wrote:
On 2016å04æ08æ 18:54, Tomeu Vizoso wrote:
On 8 April 2016 at 03:07, Mark yao <mark.yao@xxxxxxxxxxxxxx> wrote:
On 2016å04æ06æ 18:14, Tomeu Vizoso wrote:
When a plane is being disabled but it's still enabled, do check if the
previous update has been completed by reading yrgb_mst back.
Otherwise, pending pageflips would remain pending after a CRTC is
disabled.
Signed-off-by: Tomeu Vizoso <tomeu.vizoso@xxxxxxxxxxxxx>
---
drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
index a9b1e8b5ac85..f46b1fd1887b 100644
--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
@@ -1064,8 +1064,9 @@ static bool vop_win_pending_is_complete(struct
vop_win
*vop_win)
struct vop_plane_state *state = to_vop_plane_state(plane->state);
dma_addr_t yrgb_mst;
- if (!state->enable)
- return VOP_WIN_GET(vop_win->vop, vop_win->data, enable) == 0;
+ if (!state->enable &&
+ VOP_WIN_GET(vop_win->vop, vop_win->data, enable) == 0)
+ return true;
It is wrong, the patch would cause a bug.
when state->enable is 0, check yrgb_mst == state->yrgb_mst always be
true,
because state->yrgb_mst not update on plane disabled funtion, that would
cause iommu crash.
Sorry, but I don't understand where's the bug and what could cause
that crash. What the existing code was doing is saying that a pageflip
event is still pending if we have told the plane to disable but for
some reason it hasn't yet.
With this modification, if we read back that it's already disabled, we
return true as before. But if we read back that it isn't disabled yet,
then we still check the fb pointers and compare them.
The iommu mapping is removed when the _CRTC_ is disabled, and what
this series does is to wait for the pending pageflip to finish before
conitnuing with CRTC disablement.
the iommu mapping will unmap after plane disabled, we need sure that the
plane really disabled before unmap, if not, the unmap may call before plane
really disable, vop may access unmap address, then would get iommu page
fault.
Sorry, but I still don't see the error condition that you are
describing. AFAICS, the unmap will happen after the last pageflip has
completed.
About pending pageflips would remain pending, can you describe more info
about it? I think those pending pageflips should be ignore when CRTC is
disabled.
Well, right now in rockchip-drm pending pageflips won't be ignored
when a CRTC is disabled, but will be delivered when it's re-enabled.
If they would be to be ignored (understanding that as dropped), that
would require modifications to clients so they keep track of which fbs
were used in a particular crtc and destroy them when the crtc is
disabled, but that would be incorrect when using the i915 DRM driver
(I also assume others do the same). Given that the pageflip ioctl
isn't driver-specific, I think there cannot be such a difference in
behavior between drivers.
With the current behavior (pending pageflip events being delayed until
the CRTC is enabled again), compositors and other clients will be
holding on to the fb in the pending pageflip until an arbitrary point
in the future that may not ever come. To me that sounds like a serious
modification of the assumptions on fb lifecycle that might not be
warranted.
So in summary, even if I haven't found any explicit documentation on
this, I think the ABI is that any pending pageflips are to be
delivered when that CRTC is being disabled and not later.
on drivers/gpu/drm/rockchip/rockchip_drm_fb.c
drm_atomic_helper_commit_planes(dev, state, true);
rockchip_atomic_wait_for_complete(dev, state);
We set active_only = true, I think planes can only update when crtc is
active. and rockchip_atomic_wait_for_complete only wait when crtc is active.
That's fine, but if a pageflip is pending when the client requests the
CRTC to be disabled, we need to wait for the event to be emitted
before we actually disable the HW.
Hi Mark,
could you tell me if you agree that there's a bug that needs to be
solved, and if so, what do you think we should do about it?
Hi Tomeu
Sorry for reply late.
I don't agree the changes:
- if (!state->enable)
- return VOP_WIN_GET(vop_win->vop, vop_win->data, enable) == 0;
+ if (!state->enable &&
+ VOP_WIN_GET(vop_win->vop, vop_win->data, enable) == 0)
+ return true;
This changes actually would lead a bug.
when we disable a plane, the vop_win_pending_is_complete would always
return true, That is not allowed, would cause fb free too early.
Does this patch is needed for "[PATCH 2/2] drm/rockchip: vop: Wait for
pending events when disabling a CRTC"
Thanks.
Thanks,
Tomeu
Regards,
Tomeu
Thanks.
Thanks,
Tomeu
Thanks.
yrgb_mst = VOP_WIN_GET_YRGBADDR(vop_win->vop, vop_win->data);
--
ïark Yao
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
ïark Yao
_______________________________________________
dri-devel mailing list
dri-devel@xxxxxxxxxxxxxxxxxxxxx
https://lists.freedesktop.org/mailman/listinfo/dri-devel
--
ïark Yao