On Thu, Oct 9, 2014 at 7:08 PM, Thierry Reding treding@nvidia.com wrote:
On Thu, Oct 09, 2014 at 02:43:02PM +0900, Alexandre Courbot wrote:
On 10/02/2014 08:52 PM, Andrzej Hajda wrote:
Hi,
+CC possible victims
On 10/02/2014 12:52 PM, Inki Dae wrote:
On 2014년 10월 02일 17:58, Joonyoung Shim wrote:
Hi Andrzej,
On 10/01/2014 05:14 PM, Andrzej Hajda wrote:
The patch disables vblanks during dpms off only if pagefilp has not been finished. It also replaces drm_vblank_off with drm_crtc_vblank_put. It fixes issue with page_flip ioctl not being able to acquire vblank counter.
This problem isn't related with pageflip, it just causes from 7ffd7a68511c710b84db3548a1997fd2625f580a commit (drm: Always reject drm_vblank_get() after drm_vblank_off()).
We need to use drm_vblank_on() as a counterpart to drm_vblank_off() after the commit .
This patch should break also other drivers, it seems at least following drms could be affected: armada, sti, tegra.
Indeed we (tegra) have just been hit by this. The problem seems to come from the fact that we have been using drm_vblank_pre_modeset, drm_vblank_post_modeset and drm_vblank_off conjointly. All these functions depend on the value of vblank->inmodeset, and 7ffd7a68511 increases the vblank reference counter only in drm_vblank_off, which can result in the acquired reference never being released.
The following seems to fix this for Tegra, by stopping using drm_vblank_pre/post_modeset and relying on drm_vblank_off/on instead:
diff --git a/drivers/gpu/drm/tegra/dc.c b/drivers/gpu/drm/tegra/dc.c index b08df07cad47..3955d81236d0 100644 --- a/drivers/gpu/drm/tegra/dc.c +++ b/drivers/gpu/drm/tegra/dc.c @@ -739,7 +739,6 @@ static const struct drm_crtc_funcs tegra_crtc_funcs = {
static void tegra_crtc_disable(struct drm_crtc *crtc) {
struct tegra_dc *dc = to_tegra_dc(crtc); struct drm_device *drm = crtc->dev; struct drm_plane *plane;@@ -755,7 +754,7 @@ static void tegra_crtc_disable(struct drm_crtc *crtc) } }
drm_vblank_off(drm, dc->pipe);
drm_crtc_vblank_off(crtc);}
static bool tegra_crtc_mode_fixup(struct drm_crtc *crtc, @@ -844,7 +843,7 @@ static int tegra_crtc_mode_set(struct drm_crtc *crtc, u32 value; int err;
drm_vblank_pre_modeset(crtc->dev, dc->pipe);
drm_crtc_vblank_off(crtc); err = tegra_crtc_setup_clk(crtc, mode); if (err) {@@ -946,7 +945,7 @@ static void tegra_crtc_commit(struct drm_crtc *crtc) value = GENERAL_ACT_REQ | WIN_A_ACT_REQ; tegra_dc_writel(dc, value, DC_CMD_STATE_CONTROL);
drm_vblank_post_modeset(crtc->dev, dc->pipe);
drm_crtc_vblank_on(crtc);}
static void tegra_crtc_load_lut(struct drm_crtc *crtc)
Thierry, does this look ok to you?
Yes, that looks like almost the same patch that I sent out yesterday. The difference is that I didn't replace the drm_vblank_pre_modeset() call with drm_vblank_off() like you did, but rather just dropped the former.
I /think/ your version is more correct in that regard.
Feel free to take that extra line in your patch then. ;)
Thierry
But there might be another issue, which is that calls to drm_vblank_get() will return -EINVAL if invoked between drm_blank_off and drm_blank_on. Is this really the desired behavior? Can it at least happen? If so, how are drivers supposed to react to this situation?
It shouldn't happen. If drm_vblank_off() and drm_vblank_on() are called around a modeset they should never conflict with drm_vblank_get(), at least on Tegra, because the modeset and page-flip IOCTLs will be serialized.
Ok, that's good. I was just wondering whether this case has been thought of.
Actually, and seeing how drm_vblank_pre/post_modeset() have become useless (if not harmful), maybe it would be a good idea to come with a fixup patch that gets rid of them altogether and make their callers invoke drm_vblank_off/on() instead?