Re: [PATCH v2] drm/i915/dp: Switch to using the DRM function for reading DP link status

["Zanoni, Paulo R" <paulo.r.zanoni@intel.com>]

Em Qua, 2016-08-17 às 12:02 -0700, Dhinakaran Pandiyan escreveu:
> Since a DRM function that reads link DP link status is available,
> let's
> use that instead of the i915 clone.

One could describe the i915 function as a convenient wrapper instead of
a clone, since it allows passing just intel_dp as an argument and
already does the length checking, allowing callers to stay under 80
columns :). So perhaps you could have given more arguments on why the
codebase will benefit from this change.

I'm not sure whether I think the code will be better or worse with this
change, but the patch does what it says, so:
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

> 

> 
> drm_dp_dpcd_read_link_status() returns a negative error code if the
> number
> of bytes read is not DP_LINK_STATUS_SIZE, drm_dp_dpcd_access() does
> the
> length check.
> 
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> 
> v2: Eliminated redundant DP_LINK_STATUS_SIZE length check.

On our driver we usually put version information above the signatures
and tags.

> ---
>  drivers/gpu/drm/i915/intel_dp.c               | 15 ++-------------
>  drivers/gpu/drm/i915/intel_dp_link_training.c |  8 ++++++--
>  drivers/gpu/drm/i915/intel_drv.h              |  2 --
>  3 files changed, 8 insertions(+), 17 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c
> b/drivers/gpu/drm/i915/intel_dp.c
> index 8fe2afa..8eff57e 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -2863,17 +2863,6 @@ static void chv_dp_post_pll_disable(struct
> intel_encoder *encoder)
>  	chv_phy_post_pll_disable(encoder);
>  }
>  
> -/*
> - * Fetch AUX CH registers 0x202 - 0x207 which contain
> - * link status information
> - */
> -bool
> -intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t
> link_status[DP_LINK_STATUS_SIZE])
> -{
> -	return drm_dp_dpcd_read(&intel_dp->aux, DP_LANE0_1_STATUS,
> link_status,
> -				DP_LINK_STATUS_SIZE) ==
> DP_LINK_STATUS_SIZE;
> -}
> -
>  /* These are source-specific values. */
>  uint8_t
>  intel_dp_voltage_max(struct intel_dp *intel_dp)
> @@ -3896,8 +3885,8 @@ intel_dp_check_link_status(struct intel_dp
> *intel_dp)
>  
>  	WARN_ON(!drm_modeset_is_locked(&dev-
> >mode_config.connection_mutex));
>  
> -	if (!intel_dp_get_link_status(intel_dp, link_status)) {
> -		DRM_ERROR("Failed to get link status\n");
> +	if (drm_dp_dpcd_read_link_status(&intel_dp->aux,
> link_status) <= 0) {
> +		DRM_ERROR("failed to get link status\n");


You just made me run "grep DRM_ERROR * | cut -d'"' -f2 | sort" in order
to check how consistent we are regarding error message capitalization
:).

 		return;
>  	}
>  
> diff --git a/drivers/gpu/drm/i915/intel_dp_link_training.c
> b/drivers/gpu/drm/i915/intel_dp_link_training.c
> index 60fb39c..8e60e7c 100644
> --- a/drivers/gpu/drm/i915/intel_dp_link_training.c
> +++ b/drivers/gpu/drm/i915/intel_dp_link_training.c
> @@ -150,7 +150,9 @@ intel_dp_link_training_clock_recovery(struct
> intel_dp *intel_dp)
>  		uint8_t link_status[DP_LINK_STATUS_SIZE];
>  
>  		drm_dp_link_train_clock_recovery_delay(intel_dp-
> >dpcd);
> -		if (!intel_dp_get_link_status(intel_dp,
> link_status)) {
> +
> +		if (drm_dp_dpcd_read_link_status(&intel_dp->aux,
> link_status)
> +						 <= 0) {
>  			DRM_ERROR("failed to get link status\n");
>  			break;
>  		}
> @@ -258,7 +260,9 @@
> intel_dp_link_training_channel_equalization(struct intel_dp
> *intel_dp)
>  		}
>  
>  		drm_dp_link_train_channel_eq_delay(intel_dp->dpcd);
> -		if (!intel_dp_get_link_status(intel_dp,
> link_status)) {
> +
> +		if (drm_dp_dpcd_read_link_status(&intel_dp->aux,
> link_status)
> +						 <= 0) {
>  			DRM_ERROR("failed to get link status\n");
>  			break;
>  		}
> diff --git a/drivers/gpu/drm/i915/intel_drv.h
> b/drivers/gpu/drm/i915/intel_drv.h
> index b1fc67e..a3a2cb9 100644
> --- a/drivers/gpu/drm/i915/intel_drv.h
> +++ b/drivers/gpu/drm/i915/intel_drv.h
> @@ -1394,8 +1394,6 @@ intel_dp_pre_emphasis_max(struct intel_dp
> *intel_dp, uint8_t voltage_swing);
>  void intel_dp_compute_rate(struct intel_dp *intel_dp, int
> port_clock,
>  			   uint8_t *link_bw, uint8_t *rate_select);
>  bool intel_dp_source_supports_hbr2(struct intel_dp *intel_dp);
> -bool
> -intel_dp_get_link_status(struct intel_dp *intel_dp, uint8_t
> link_status[DP_LINK_STATUS_SIZE]);
>  
>  static inline unsigned int intel_dp_unused_lane_mask(int lane_count)
>  {
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