Commit bb24153a authored Jul 25, 2018 by Mikulas Patocka Committed by Bartlomiej Zolnierkiewicz Jul 25, 2018

udlfb: set optimal write delay



The default delay 5 jiffies is too much when the kernel is compiled with
HZ=100 - it results in jumpy cursor in Xwindow.

In order to find out the optimal delay, I benchmarked the driver on
1280x720x30fps video. I found out that with HZ=1000, 10ms is acceptable,
but with HZ=250 or HZ=300, we need 4ms, so that the video is played
without any frame skips.

This patch changes the delay to this value.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

parent 2c29cfc3

include/video/udlfb.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -88,7 +88,7 @@ struct dlfb_data {
		#define MIN_RAW_PIX_BYTES 2
		#define MIN_RAW_CMD_BYTES (RAW_HEADER_BYTES + MIN_RAW_PIX_BYTES)

		#define DL_DEFIO_WRITE_DELAY 5 /* fb_deferred_io.delay in jiffies */
		#define DL_DEFIO_WRITE_DELAY msecs_to_jiffies(HZ <= 300 ? 4 : 10) /* optimal value for 720p video */
		#define DL_DEFIO_WRITE_DISABLE (HZ60) / "disable" with long delay */

		/* remove these once align.h patch is taken into kernel */

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