Re: [PATCH] drm/i915/glk: Use cached RCOMP value when re-enabling DPIO Phy

[Rodrigo Vivi <rodrigo.vivi@intel.com>]

On Thu, Nov 15, 2018 at 11:48:06AM -0800, clinton.a.taylor@intel.com wrote:
> From: Clint Taylor <clinton.a.taylor@intel.com>
> 
> The calibration RCOMP value in PORT_TX_DW6 in stored in dev_priv during
> driver init. Use this value instead of reading the register again as the
> power well for PORTA RCOMP register may not be enabled and will return
> 0xFFFFFFFF instead of the computed value.

I have the feeling this is not the right fix for the issue.

The function where this is stored is the same function this patch is
changing. just a little bit earlier. So if power well is not enabled
now it was probably not enabled a few cycles earlier.

Also if it is just a matter of power well it is just to make sure
that we make sure to grab the right power domain and relase when
this is not needed.

Thanks,
Rodrigo.

> 
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Signed-off-by: Clint Taylor <clinton.a.taylor@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dpio_phy.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dpio_phy.c b/drivers/gpu/drm/i915/intel_dpio_phy.c
> index 3c7f10d..7cee57f 100644
> --- a/drivers/gpu/drm/i915/intel_dpio_phy.c
> +++ b/drivers/gpu/drm/i915/intel_dpio_phy.c
> @@ -422,8 +422,12 @@ static void _bxt_ddi_phy_init(struct drm_i915_private *dev_priv,
>  		 * the corresponding calibrated value from PHY1, and disable
>  		 * the automatic calibration on PHY0.
>  		 */
> -		val = dev_priv->bxt_phy_grc = bxt_get_grc(dev_priv,
> -							  phy_info->rcomp_phy);
> +		if (!dev_priv->bxt_phy_grc)
> +			val = dev_priv->bxt_phy_grc = bxt_get_grc(dev_priv,
> +								  phy_info->rcomp_phy);
> +		else
> +			val = dev_priv->bxt_phy_grc;
> +
>  		grc_code = val << GRC_CODE_FAST_SHIFT |
>  			   val << GRC_CODE_SLOW_SHIFT |
>  			   val;
> -- 
> 1.9.1
> 
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