Re: [PATCHv2 42/45] drm: omapdrm: add omap_atomic_wait_for_gos()

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Tomi,

Thank you for the patch.

On Thursday 04 June 2015 12:02:59 Tomi Valkeinen wrote:
> omap_atomic_complete() uses drm_atomic_helper_wait_for_vblanks() to wait
> for all operations to finish. That works, but can easily cause waits for
> vblanks when no wait is actually necessary.

It actually doesn't work properly, as a full mode set without any change to 
framebuffers will need to reenable planes after enabling the CRTC and thus 
sets the go bit, but the drm_atomic_helper_wait_for_vblanks() function called 
during atomic commit waits for vblank only on CRTCs that have seen a page 
flip. This leads to missing waits, resulting in a go busy warning if the next 
.atomic_flush() call occurs too soon.

Your patch fixes that issue, so I'm fine with the code, but I think the commit 
message should be fixed. Then,

Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> This patch adds omap_atomic_wait_for_gos() and uses it instead.
> omap_atomic_wait_for_gos() waits for the GO bit to get unset for all
> relevant crtcs.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> ---
>  drivers/gpu/drm/omapdrm/omap_crtc.c |  7 +++++++
>  drivers/gpu/drm/omapdrm/omap_drv.c  | 31 ++++++++++++++++++++++++++++++-
>  drivers/gpu/drm/omapdrm/omap_drv.h  |  1 +
>  3 files changed, 38 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_crtc.c
> b/drivers/gpu/drm/omapdrm/omap_crtc.c index 2c0d91a67418..8f905d2c8074
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_crtc.c
> +++ b/drivers/gpu/drm/omapdrm/omap_crtc.c
> @@ -80,6 +80,13 @@ enum omap_channel omap_crtc_channel(struct drm_crtc
> *crtc) return omap_crtc->channel;
>  }
> 
> +bool omap_crtc_needs_wait(struct drm_crtc *crtc)
> +{
> +	struct omap_crtc *omap_crtc = to_omap_crtc(crtc);
> +
> +	return dispc_mgr_go_busy(omap_crtc->channel);
> +}
> +
>  /*
> ---------------------------------------------------------------------------
> -- * DSS Manager Functions
>   */
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.c
> b/drivers/gpu/drm/omapdrm/omap_drv.c index 50f555530e55..c03405593f9f
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.c
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.c
> @@ -66,6 +66,35 @@ struct omap_atomic_state_commit {
>  	u32 crtcs;
>  };
> 
> +static void omap_atomic_wait_for_gos(struct drm_device *dev,
> +					 struct drm_atomic_state *old_state)
> +{
> +	struct drm_crtc *crtc;
> +	struct drm_crtc_state *old_crtc_state;
> +	int i, ret;
> +
> +	for_each_crtc_in_state(old_state, crtc, old_crtc_state, i) {
> +		if (!crtc->state->enable)
> +			continue;
> +
> +		if (!omap_crtc_needs_wait(crtc))
> +			continue;
> +
> +		ret = drm_crtc_vblank_get(crtc);
> +		if (ret != 0)
> +			continue;
> +
> +		ret = wait_event_timeout(dev->vblank[i].queue,
> +					 !omap_crtc_needs_wait(crtc),
> +					 msecs_to_jiffies(50));
> +		if (!ret)
> +			dev_warn(dev->dev,
> +				 "atomic flush timeout (pipe %u)!\n", i);
> +
> +		drm_crtc_vblank_put(crtc);
> +	}
> +}
> +
>  static void omap_atomic_complete(struct omap_atomic_state_commit *commit)
>  {
>  	struct drm_device *dev = commit->dev;
> @@ -79,7 +108,7 @@ static void omap_atomic_complete(struct
> omap_atomic_state_commit *commit) drm_atomic_helper_commit_planes(dev,
> old_state);
>  	drm_atomic_helper_commit_modeset_enables(dev, old_state);
> 
> -	drm_atomic_helper_wait_for_vblanks(dev, old_state);
> +	omap_atomic_wait_for_gos(dev, old_state);
> 
>  	drm_atomic_helper_cleanup_planes(dev, old_state);
> 
> diff --git a/drivers/gpu/drm/omapdrm/omap_drv.h
> b/drivers/gpu/drm/omapdrm/omap_drv.h index 0b7a055bf007..27bbf7c4d76e
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_drv.h
> +++ b/drivers/gpu/drm/omapdrm/omap_drv.h
> @@ -147,6 +147,7 @@ void omap_crtc_pre_init(void);
>  void omap_crtc_pre_uninit(void);
>  struct drm_crtc *omap_crtc_init(struct drm_device *dev,
>  		struct drm_plane *plane, enum omap_channel channel, int id);
> +bool omap_crtc_needs_wait(struct drm_crtc *crtc);
> 
>  struct drm_plane *omap_plane_init(struct drm_device *dev,
>  		int id, enum drm_plane_type type);

-- 
Regards,

Laurent Pinchart
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