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

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 06-07-17 om 13:09 schreef Tomeu Vizoso:
> Looks good to me:
>
> Reviewed-by: Tomeu Vizoso <tomeu.vizoso@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@linux.intel.com>
Fixes: e8fa5671183c ("drm: crc: Wait for a frame before returning from open()")
Testcase: debugfs_test.read_all_entries
---
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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