[Intel-gfx] [PATCH i-g-t 1/2] lib/igt_debugfs: Throw away the two first CRCs

[Daniel Vetter]

On Tue, Dec 09, 2014 at 05:25:16PM +0200, ville.syrjala at linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> 
> On CHV we sometimes see not just one but two bad CRCs. No real idea
> what would cause that, but let's just throw away the second CRC as
> well to gain some stability for the tests.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> ---
>  lib/igt_debugfs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/igt_debugfs.c b/lib/igt_debugfs.c
> index 0b098ee..b44333e 100644
> --- a/lib/igt_debugfs.c
> +++ b/lib/igt_debugfs.c
> @@ -425,8 +425,11 @@ void igt_pipe_crc_start(igt_pipe_crc_t *pipe_crc)
>  	/*
>  	 * For some no yet identified reason, the first CRC is bonkers. So
>  	 * let's just wait for the next vblank and read out the buggy result.
> +	 *
> +	 * On CHV sometimes the second CRC is bonkers as well, so don't trust
> +	 * that one either.
>  	 */
> -	igt_pipe_crc_get_crcs(pipe_crc, 1, &crcs);
> +	igt_pipe_crc_get_crcs(pipe_crc, 2, &crcs);

I wonder a bit whether we shouldn't push these vblank waits into the
kernel, maybe with some comments.

Wrt chv: Is this only on DP outputs? could be that the scrambler takes 2
vblanks (1 to set the bit, 1 to actually act on it) to go into the new
fancy mode.
-Daniel

>  	free(crcs);
>  }
>  
> -- 
> 2.0.4
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch