[Intel-gfx] [PATCH] drm/crc: Only open CRC on atomic drivers when the CRTC is active.

[Daniel Vetter]

On Thu, Jul 06, 2017 at 03:03:15PM +0200, Maarten Lankhorst wrote:
> Op 06-07-17 om 13:09 schreef Tomeu Vizoso:
> > Looks good to me:
> >
> > Reviewed-by: Tomeu Vizoso <tomeu.vizoso at collabora.com>
> >
> > I guess you have tested this with IGT? In any case, I think it would
> > be good to mention how a patch has been tested in the changelog. That
> > can be very useful to others if things go wrong at some point.
> Testcase: debugfs_test.read_all_entries
> 
> But I hit it by doing a recursive grep, which I guess is the same thing here. :)
> 
> One further improvement I wanted to do was reject opening the CRC with -EIO
> when the crtc is not active, that way the above test will not hang.
> Does the below patch also look good to you?
> 
> ----8<-----
> Commit e8fa5671183c ("drm: crc: Wait for a frame before returning
> from open()") adds a wait for CRC frame, but with the CRTC off
> this will never be generated. For atomic drivers we know if a CRTC
> is active through crtc_state->active, so when inactive reject the
> open with -EIO.
> 
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Fixes: e8fa5671183c ("drm: crc: Wait for a frame before returning from open()")
> Testcase: debugfs_test.read_all_entries

At least for the semantics I think this makes sense. Opening the CRC file
when the crtc is off is undefined.

Reviewed-by: Daniel Vetter <daniel.vetter at ffwll.ch>

But pls get Tomeu's ack too.

Thanks, Daniel


> ---
> diff --git a/drivers/gpu/drm/drm_debugfs_crc.c b/drivers/gpu/drm/drm_debugfs_crc.c
> index d0ea4627a093..f9e26dda56d6 100644
> --- a/drivers/gpu/drm/drm_debugfs_crc.c
> +++ b/drivers/gpu/drm/drm_debugfs_crc.c
> @@ -154,6 +154,19 @@ static int crtc_crc_open(struct inode *inode, struct file *filep)
>  	size_t values_cnt;
>  	int ret = 0;
>  
> +	if (drm_drv_uses_atomic_modeset(crtc->dev)) {
> +		ret = drm_modeset_lock_interruptible(&crtc->mutex, NULL);
> +		if (ret)
> +			return ret;
> +
> +		if (!crtc->state->active)
> +			ret = -EIO;
> +		drm_modeset_unlock(&crtc->mutex);
> +
> +		if (ret)
> +			return ret;
> +	}
> +
>  	spin_lock_irq(&crc->lock);
>  	if (!crc->opened)
>  		crc->opened = true;
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch