Re: [PATCH 7/7] drm/i915: Dont -ETIMEDOUT on identical new and previous (count, crc).

From: Rafael Antognolli <rafael.antognolli@intel.com>
To: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 7/7] drm/i915: Dont -ETIMEDOUT on identical new and previous (count, crc).
Date: Tue, 28 Jul 2015 13:25:39 -0700	[thread overview]
Message-ID: <20150728202539.GD5902@intel.com> (raw)
In-Reply-To: <1437694550-5667-6-git-send-email-rodrigo.vivi@intel.com>

On Thu, Jul 23, 2015 at 04:35:50PM -0700, Rodrigo Vivi wrote:
> By Vesa DP 1.2 spec TEST_CRC_COUNT is a "4 bit wrap counter which
> increments each time the TEST_CRC_x_x are updated."
> 
> However if we are trying to verify the screen hasn't changed we get
> same (count, crc) pair twice. Without this patch we would return
> -ETIMEOUT in this case.
> 
> So, if in 6 vblanks the pair (count, crc) hasn't changed we
> return it anyway instead of returning error and let test case decide
> if it was right or not.
> 
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

Looks good.

> ---
>  drivers/gpu/drm/i915/intel_dp.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index c7372a1..e99ec7a 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -4028,6 +4028,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>  	u8 buf;
>  	int count, ret;
>  	int attempts = 6;
> +	bool old_equal_new;
>  
>  	ret = intel_dp_sink_crc_start(intel_dp);
>  	if (ret)
> @@ -4042,6 +4043,7 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>  			goto stop;
>  		}
>  		count = buf & DP_TEST_COUNT_MASK;
> +
>  		/*
>  		 * Count might be reset during the loop. In this case
>  		 * last known count needs to be reset as well.
> @@ -4053,17 +4055,24 @@ int intel_dp_sink_crc(struct intel_dp *intel_dp, u8 *crc)
>  			ret = -EIO;
>  			goto stop;
>  		}
> -	} while (--attempts && (count == 0 || (count == intel_dp->sink_crc.last_count &&
> -					       !memcmp(intel_dp->sink_crc.last_crc, crc,
> -						       6 * sizeof(u8)))));
> +
> +		old_equal_new = (count == intel_dp->sink_crc.last_count &&
> +				 !memcmp(intel_dp->sink_crc.last_crc, crc,
> +					 6 * sizeof(u8)));
> +
> +	} while (--attempts && (count == 0 || old_equal_new));
>  
>  	intel_dp->sink_crc.last_count = buf & DP_TEST_COUNT_MASK;
>  	memcpy(intel_dp->sink_crc.last_crc, crc, 6 * sizeof(u8));
>  
>  	if (attempts == 0) {
> -		DRM_DEBUG_KMS("Panel is unable to calculate CRC after 6 vblanks\n");
> -		ret = -ETIMEDOUT;
> -		goto stop;
> +		if (old_equal_new) {
> +			DRM_DEBUG_KMS("Unreliable Sink CRC counter: Current returned CRC is identical to the previous one\n");

Isn't this line a little too long?

> +		} else {
> +			DRM_ERROR("Panel is unable to calculate any CRC after 6 vblanks\n");
> +			ret = -ETIMEDOUT;
> +			goto stop;
> +		}
>  	}
>  
>  stop:
> -- 
> 2.1.0
> 
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