Re: [PATCH 2/2] drm/i915: Adjust sideband locking a bit for CHV/VLV

[Jani Nikula <jani.nikula@linux.intel.com>]

On Tue, 26 May 2015, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> chv_enable_pll() doesn't need to hold sb_lock for the entire duration of
> the function. Drop the lock as soon as possible.
>
> valleyview_set_cdclk() does a potential lock+unlock+lock+unlock cycle
> with sb_lock. Move Grab the lock a few lines earlier so we can make do

Move Grab?

Anyway, both patches are

Reviewed-by: Jani Nikula <jani.nikula@intel.com>


> with a single lock+unlock cycle always.
>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 72b6529..067b1de 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -1668,6 +1668,8 @@ static void chv_enable_pll(struct intel_crtc *crtc,
>  	tmp |= DPIO_DCLKP_EN;
>  	vlv_dpio_write(dev_priv, pipe, CHV_CMN_DW14(port), tmp);
>  
> +	mutex_unlock(&dev_priv->sb_lock);
> +
>  	/*
>  	 * Need to wait > 100ns between dclkp clock enable bit and PLL enable.
>  	 */
> @@ -1683,8 +1685,6 @@ static void chv_enable_pll(struct intel_crtc *crtc,
>  	/* not sure when this should be written */
>  	I915_WRITE(DPLL_MD(pipe), pipe_config->dpll_hw_state.dpll_md);
>  	POSTING_READ(DPLL_MD(pipe));
> -
> -	mutex_unlock(&dev_priv->sb_lock);
>  }
>  
>  static int intel_num_dvo_pipes(struct drm_device *dev)
> @@ -5780,12 +5780,13 @@ static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
>  	}
>  	mutex_unlock(&dev_priv->rps.hw_lock);
>  
> +	mutex_lock(&dev_priv->sb_lock);
> +
>  	if (cdclk == 400000) {
>  		u32 divider;
>  
>  		divider = DIV_ROUND_CLOSEST(dev_priv->hpll_freq << 1, cdclk) - 1;
>  
> -		mutex_lock(&dev_priv->sb_lock);
>  		/* adjust cdclk divider */
>  		val = vlv_cck_read(dev_priv, CCK_DISPLAY_CLOCK_CONTROL);
>  		val &= ~DISPLAY_FREQUENCY_VALUES;
> @@ -5796,10 +5797,8 @@ static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
>  			      DISPLAY_FREQUENCY_STATUS) == (divider << DISPLAY_FREQUENCY_STATUS_SHIFT),
>  			     50))
>  			DRM_ERROR("timed out waiting for CDclk change\n");
> -		mutex_unlock(&dev_priv->sb_lock);
>  	}
>  
> -	mutex_lock(&dev_priv->sb_lock);
>  	/* adjust self-refresh exit latency value */
>  	val = vlv_bunit_read(dev_priv, BUNIT_REG_BISOC);
>  	val &= ~0x7f;
> @@ -5813,6 +5812,7 @@ static void valleyview_set_cdclk(struct drm_device *dev, int cdclk)
>  	else
>  		val |= 3000 / 250; /* 3.0 usec */
>  	vlv_bunit_write(dev_priv, BUNIT_REG_BISOC, val);
> +
>  	mutex_unlock(&dev_priv->sb_lock);
>  
>  	vlv_update_cdclk(dev);
> -- 
> 2.3.6
>
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-- 
Jani Nikula, Intel Open Source Technology Center
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