drm/i915: Implement blocking read for pipe CRC files
seq_file is not quite the right interface for these ones. We have a
circular buffer with a new entry per vblank on one side and a process
wanting to dequeue the CRC with a read().
It's quite racy to wait for vblank in user land and then try to read a
pipe_crc file, sometimes the CRC interrupt hasn't been fired and we end
up with an EOF.
So, let's have the read on the pipe_crc file block until the interrupt
gives us a new entry. At that point we can wake the reading process.
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index b201a21..b2be057 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1221,6 +1221,8 @@
head = (head + 1) & (INTEL_PIPE_CRC_ENTRIES_NR - 1);
atomic_set(&pipe_crc->head, head);
+
+ wake_up_interruptible(&pipe_crc->wq);
}
#else
static void ivb_pipe_crc_update(struct drm_device *dev, int pipe) {}