Re: [PATCH 5/7] drm/i915: disable CLKOUT_DP when it's not needed

[Ben Widawsky <ben@bwidawsk.net>]

On Fri, Jul 12, 2013 at 02:19:40PM -0300, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni@intel.com>
> 
> We currently don't support HDMI clock bending nor use SSC for DP or
> HDMI on Haswell, so the only case where we need CLKOUT_DP is for VGA.
> 
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 38 ++++++++++++++++++++++++++++++++----
>  1 file changed, 34 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 5f3b636..059c9a8 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5305,6 +5305,36 @@ static void lpt_enable_clkout_dp(struct drm_device *dev, bool with_spread,
>  	mutex_unlock(&dev_priv->dpio_lock);
>  }
>  
> +/* Sequence to disable CLKOUT_DP */
> +static void lpt_disable_clkout_dp(struct drm_device *dev)
> +{
> +	struct drm_i915_private *dev_priv = dev->dev_private;
> +	uint32_t tmp;
> +
> +	mutex_lock(&dev_priv->dpio_lock);
> +
> +	if (IS_ULT(dev_priv->dev)) {
> +		tmp = intel_sbi_read(dev_priv, SBI_GEN0, SBI_ICLK);
> +		tmp &= ~SBI_GEN0_ENABLE;
> +		intel_sbi_write(dev_priv, SBI_GEN0, tmp, SBI_ICLK);
> +	} else {
> +		tmp = intel_sbi_read(dev_priv, SBI_DBUFF0, SBI_ICLK);
> +		tmp &= ~SBI_DBUFF0_ENABLE;
> +		intel_sbi_write(dev_priv, SBI_DBUFF0, tmp, SBI_ICLK);
> +	}
> +
> +	tmp = intel_sbi_read(dev_priv, SBI_SSCCTL, SBI_ICLK);
> +	if (!(tmp & SBI_SSCCTL_PATHALT)) {
> +		tmp |= SBI_SSCCTL_PATHALT;
> +		intel_sbi_write(dev_priv, SBI_SSCCTL, tmp, SBI_ICLK);
> +		udelay(32);
> +	}

Apologies if this is stupid, I'm new to this part of the doc, shouldn't
it be:
if (tmp & ~SBI_SSCCTL_DISABLE == 0)

> +	tmp |= SBI_SSCCTL_DISABLE;
> +	intel_sbi_write(dev_priv, SBI_SSCCTL, tmp, SBI_ICLK);
> +
> +	mutex_unlock(&dev_priv->dpio_lock);
> +}
> +
>  static void lpt_init_pch_refclk(struct drm_device *dev)
>  {
>  	struct drm_mode_config *mode_config = &dev->mode_config;
> @@ -5319,10 +5349,10 @@ static void lpt_init_pch_refclk(struct drm_device *dev)
>  		}
>  	}
>  
> -	if (!has_vga)
> -		return;
> -
> -	lpt_enable_clkout_dp(dev, true, true);
> +	if (has_vga)
> +		lpt_enable_clkout_dp(dev, true, true);
> +	else
> +		lpt_disable_clkout_dp(dev);
>  }



-- 
Ben Widawsky, Intel Open Source Technology Center