[Intel-gfx] [PATCH 1/8] drm/i915: Skip modifying PCH DREF if not changing clock sources

[Daniel Vetter]

On Wed, Feb 06, 2013 at 11:10:21AM +0000, Chris Wilson wrote:
> Modifying the clock sources (via the DREF control on the PCH) is a slow
> multi-stage process as we need to let the clocks stabilise between each
> stage. If we are not actually changing the clock sources, then we can
> return early.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

One idea I've been pondering for the refclock stuff is to simply shovel
this into the ->modeset_global_resources callback. That way no clever
tricks are required, and we'd avoid this for all cases where fastboot
works complety. Presumably ofc that the bios didn't set up a config which
does not work.

As a bonus, we could only set up the refclocks the new configuration
actually needs, i.e. filter for encoder->crtc != NULL ... A bit a risky
patch, but might uncover some subtle bugs if we do the refclock adjusting
more often.

Too insane?
-Daniel
> ---
>  drivers/gpu/drm/i915/intel_display.c |   83 +++++++++++++++++++++++++---------
>  1 file changed, 61 insertions(+), 22 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index d75c6a0..f1dbd01 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -4749,7 +4749,7 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	struct drm_mode_config *mode_config = &dev->mode_config;
>  	struct intel_encoder *encoder;
> -	u32 temp;
> +	u32 val, final;
>  	bool has_lvds = false;
>  	bool has_cpu_edp = false;
>  	bool has_pch_edp = false;
> @@ -4792,70 +4792,109 @@ static void ironlake_init_pch_refclk(struct drm_device *dev)
>  	 * PCH B stepping, previous chipset stepping should be
>  	 * ignoring this setting.
>  	 */
> -	temp = I915_READ(PCH_DREF_CONTROL);
> +	val = I915_READ(PCH_DREF_CONTROL);
> +
> +	/* As we must carefully and slowly disable/enable each source in turn,
> +	 * compute the final state we want first and check if we need to
> +	 * make any changes at all.
> +	 */
> +	final = val;
> +	final &= ~DREF_NONSPREAD_SOURCE_MASK;
> +	if (has_ck505)
> +		final |= DREF_NONSPREAD_CK505_ENABLE;
> +	else
> +		final |= DREF_NONSPREAD_SOURCE_ENABLE;
> +
> +	final &= ~DREF_SSC_SOURCE_MASK;
> +	final &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
> +	final &= ~DREF_SSC1_ENABLE;
> +
> +	if (has_panel) {
> +		final |= DREF_SSC_SOURCE_ENABLE;
> +
> +		if (intel_panel_use_ssc(dev_priv) && can_ssc)
> +			final |= DREF_SSC1_ENABLE;
> +
> +		if (has_cpu_edp) {
> +			if (intel_panel_use_ssc(dev_priv) && can_ssc)
> +				final |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
> +			else
> +				final |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
> +		} else
> +			final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
> +	} else {
> +		final |= DREF_SSC_SOURCE_DISABLE;
> +		final |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
> +	}
> +
> +	if (final == val)
> +		return;
> +
>  	/* Always enable nonspread source */
> -	temp &= ~DREF_NONSPREAD_SOURCE_MASK;
> +	val &= ~DREF_NONSPREAD_SOURCE_MASK;
>  
>  	if (has_ck505)
> -		temp |= DREF_NONSPREAD_CK505_ENABLE;
> +		val |= DREF_NONSPREAD_CK505_ENABLE;
>  	else
> -		temp |= DREF_NONSPREAD_SOURCE_ENABLE;
> +		val |= DREF_NONSPREAD_SOURCE_ENABLE;
>  
>  	if (has_panel) {
> -		temp &= ~DREF_SSC_SOURCE_MASK;
> -		temp |= DREF_SSC_SOURCE_ENABLE;
> +		val &= ~DREF_SSC_SOURCE_MASK;
> +		val |= DREF_SSC_SOURCE_ENABLE;
>  
>  		/* SSC must be turned on before enabling the CPU output  */
>  		if (intel_panel_use_ssc(dev_priv) && can_ssc) {
>  			DRM_DEBUG_KMS("Using SSC on panel\n");
> -			temp |= DREF_SSC1_ENABLE;
> +			val |= DREF_SSC1_ENABLE;
>  		} else
> -			temp &= ~DREF_SSC1_ENABLE;
> +			val &= ~DREF_SSC1_ENABLE;
>  
>  		/* Get SSC going before enabling the outputs */
> -		I915_WRITE(PCH_DREF_CONTROL, temp);
> +		I915_WRITE(PCH_DREF_CONTROL, val);
>  		POSTING_READ(PCH_DREF_CONTROL);
>  		udelay(200);
>  
> -		temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
> +		val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
>  
>  		/* Enable CPU source on CPU attached eDP */
>  		if (has_cpu_edp) {
>  			if (intel_panel_use_ssc(dev_priv) && can_ssc) {
>  				DRM_DEBUG_KMS("Using SSC on eDP\n");
> -				temp |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
> +				val |= DREF_CPU_SOURCE_OUTPUT_DOWNSPREAD;
>  			}
>  			else
> -				temp |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
> +				val |= DREF_CPU_SOURCE_OUTPUT_NONSPREAD;
>  		} else
> -			temp |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
> +			val |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
>  
> -		I915_WRITE(PCH_DREF_CONTROL, temp);
> +		I915_WRITE(PCH_DREF_CONTROL, val);
>  		POSTING_READ(PCH_DREF_CONTROL);
>  		udelay(200);
>  	} else {
>  		DRM_DEBUG_KMS("Disabling SSC entirely\n");
>  
> -		temp &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
> +		val &= ~DREF_CPU_SOURCE_OUTPUT_MASK;
>  
>  		/* Turn off CPU output */
> -		temp |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
> +		val |= DREF_CPU_SOURCE_OUTPUT_DISABLE;
>  
> -		I915_WRITE(PCH_DREF_CONTROL, temp);
> +		I915_WRITE(PCH_DREF_CONTROL, val);
>  		POSTING_READ(PCH_DREF_CONTROL);
>  		udelay(200);
>  
>  		/* Turn off the SSC source */
> -		temp &= ~DREF_SSC_SOURCE_MASK;
> -		temp |= DREF_SSC_SOURCE_DISABLE;
> +		val &= ~DREF_SSC_SOURCE_MASK;
> +		val |= DREF_SSC_SOURCE_DISABLE;
>  
>  		/* Turn off SSC1 */
> -		temp &= ~ DREF_SSC1_ENABLE;
> +		val &= ~ DREF_SSC1_ENABLE;
>  
> -		I915_WRITE(PCH_DREF_CONTROL, temp);
> +		I915_WRITE(PCH_DREF_CONTROL, val);
>  		POSTING_READ(PCH_DREF_CONTROL);
>  		udelay(200);
>  	}
> +
> +	BUG_ON(val != final);
>  }
>  
>  /* Sequence to enable CLKOUT_DP for FDI usage and configure PCH FDI I/O. */
> -- 
> 1.7.10.4
> 
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch