Re: [PATCH 2/2] drm/i915: Allow PCH DPLL sharing regardles of DPLL_SDVO_HIGH_SPEED

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Nov 25, 2015 at 04:35:31PM +0200, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> DPLL_SDVO_HIGH_SPEED must be set for SDVO/HDMI/DP, but nowhere is it
> forbidden to set it for LVDS/CRT as well. So let's move it out of the
> ironlake_compute_dpll() and just do it on demand in the pll enable hook.
> This allows the PLL to be shared in more cases when dealing with
> different output types.
> 
> Note that we must now call the pll enable hook regarless of the current
> pll state, so that DPLL_SDVO_HIGH_SPEED gets updated appropriately.
> 
> FIXME: maybe better to add a separate hook for the "pll already enabled"
> case?
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 29 +++++++++++++++++++++--------
>  1 file changed, 21 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 26cafeea2845..ae58f1105458 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -1908,6 +1908,8 @@ static void intel_enable_shared_dpll(struct intel_crtc *crtc)
>  	if (pll->active++) {
>  		WARN_ON(!pll->on);
>  		assert_shared_dpll_enabled(dev_priv, pll);
> +		/* to update high speed IO clock state */
> +		pll->enable(dev_priv, pll);
>  		return;
>  	}
>  	WARN_ON(pll->on);
> @@ -8942,11 +8944,6 @@ static uint32_t ironlake_compute_dpll(struct intel_crtc *intel_crtc,
>  	dpll |= (crtc_state->pixel_multiplier - 1)
>  		<< PLL_REF_SDVO_HDMI_MULTIPLIER_SHIFT;
>  
> -	if (is_sdvo)
> -		dpll |= DPLL_SDVO_HIGH_SPEED;
> -	if (crtc_state->has_dp_encoder)
> -		dpll |= DPLL_SDVO_HIGH_SPEED;
> -
>  	/* compute bitmask from p1 value */
>  	dpll |= (1 << (crtc_state->dpll.p1 - 1)) << DPLL_FPA01_P1_POST_DIV_SHIFT;
>  	/* also FPA1 */
> @@ -13626,7 +13623,7 @@ static bool ibx_pch_dpll_get_hw_state(struct drm_i915_private *dev_priv,
>  		return false;
>  
>  	val = I915_READ(PCH_DPLL(pll->id));
> -	hw_state->dpll = val;
> +	hw_state->dpll = val & ~DPLL_SDVO_HIGH_SPEED;
>  	hw_state->fp0 = I915_READ(PCH_FP0(pll->id));
>  	hw_state->fp1 = I915_READ(PCH_FP1(pll->id));
>  
> @@ -13643,10 +13640,26 @@ static void ibx_pch_dpll_mode_set(struct drm_i915_private *dev_priv,
>  static void ibx_pch_dpll_enable(struct drm_i915_private *dev_priv,
>  				struct intel_shared_dpll *pll)
>  {
> +	struct drm_device *dev = dev_priv->dev;
> +	struct intel_crtc *crtc;
> +	u32 dpll = pll->config.hw_state.dpll;
> +
> +	/* Configure high speed IO clock as needed */
> +	for_each_intel_crtc(dev, crtc) {
> +		if (intel_crtc_to_shared_dpll(crtc) == pll &&
> +		    crtc->config->base.active &&
> +		    (crtc->config->has_dp_encoder ||
> +		     intel_pipe_has_type(crtc, INTEL_OUTPUT_SDVO) ||
> +		     intel_pipe_has_type(crtc, INTEL_OUTPUT_HDMI))) {
> +			dpll |= DPLL_SDVO_HIGH_SPEED;
> +			break;
> +		}
> +	}

This is a bit ugly. What about adding a needs_5x_clock to struct
intel_shared_dpll_config (i.e. outside of the hw pll state to avoid
unsharing and pipe checker warnings)? ilk_compute_dpll would set that, and
this function here obeys.

Clearing would only happen when we completely disable a pll after the last
user is gone.

I just find looping over anything in modeset code offensive ;-)

Also please add your extended bspec research to the commit message.
-Daniel

> +
>  	/* PCH refclock must be enabled first */
>  	ibx_assert_pch_refclk_enabled(dev_priv);
>  
> -	I915_WRITE(PCH_DPLL(pll->id), pll->config.hw_state.dpll);
> +	I915_WRITE(PCH_DPLL(pll->id), dpll);
>  
>  	/* Wait for the clocks to stabilize. */
>  	POSTING_READ(PCH_DPLL(pll->id));
> @@ -13657,7 +13670,7 @@ static void ibx_pch_dpll_enable(struct drm_i915_private *dev_priv,
>  	 *
>  	 * So write it again.
>  	 */
> -	I915_WRITE(PCH_DPLL(pll->id), pll->config.hw_state.dpll);
> +	I915_WRITE(PCH_DPLL(pll->id), dpll);
>  	POSTING_READ(PCH_DPLL(pll->id));
>  	udelay(200);
>  }
> -- 
> 2.4.10
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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