Re: [PATCH 07/21] drm/i915: Allow enable/disable of DPLL0 around cdclk changes on SKL

[Imre Deak <imre.deak@intel.com>]

On pe, 2016-05-13 at 23:41 +0300, ville.syrjala@linux.intel.com wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> 
> In case we originally guessed wrong which lcpll vco frequency to use,
> we will need to shut down the pll and restart it when reprogamming the
> cdclk.
> 
> This also allows us to track the actual vco frequency in dev_priv
> instead of just a guess.
> 
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_display.c | 54 +++++++++++++++++++-----------------
>  1 file changed, 29 insertions(+), 25 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 95997eed9dd6..cd2809179042 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -5626,6 +5626,8 @@ skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
>  
>  	if (wait_for(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK, 5))
>  		DRM_ERROR("DPLL0 not locked\n");
> +
> +	dev_priv->skl_vco_freq = vco;
>  }
>  
>  static void
> @@ -5634,6 +5636,8 @@ skl_dpll0_disable(struct drm_i915_private *dev_priv)
>  	I915_WRITE(LCPLL1_CTL, I915_READ(LCPLL1_CTL) & ~LCPLL_PLL_ENABLE);
>  	if (wait_for(!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_LOCK), 1))
>  		DRM_ERROR("Couldn't disable DPLL0\n");
> +
> +	dev_priv->skl_vco_freq = 0;
>  }
>  
>  static bool skl_cdclk_pcu_ready(struct drm_i915_private *dev_priv)
> @@ -5663,12 +5667,14 @@ static bool skl_cdclk_wait_for_pcu_ready(struct drm_i915_private *dev_priv)
>  	return false;
>  }
>  
> -static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
> +static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk, int vco)
>  {
>  	struct drm_device *dev = dev_priv->dev;
>  	u32 freq_select, pcu_ack;
>  
> -	DRM_DEBUG_DRIVER("Changing CDCLK to %dKHz\n", cdclk);
> +	WARN_ON((cdclk == 24000) != (vco == 0));
> +
> +	DRM_DEBUG_DRIVER("Changing CDCLK to %d kHz (VCO %d MHz)\n", cdclk, vco);
>  
>  	if (!skl_cdclk_wait_for_pcu_ready(dev_priv)) {
>  		DRM_ERROR("failed to inform PCU about cdclk change\n");
> @@ -5699,6 +5705,13 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv, int cdclk)
>  		break;
>  	}
>  
> +	if (dev_priv->skl_vco_freq != 0 &&
> +	    dev_priv->skl_vco_freq != vco)
> +		skl_dpll0_disable(dev_priv);
> +
> +	if (dev_priv->skl_vco_freq != vco)
> +		skl_dpll0_enable(dev_priv, vco);
> +
>  	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(cdclk));
>  	POSTING_READ(CDCLK_CTL);
>  
> @@ -5721,26 +5734,21 @@ void skl_uninit_cdclk(struct drm_i915_private *dev_priv)
>  	if (I915_READ(DBUF_CTL) & DBUF_POWER_STATE)
>  		DRM_ERROR("DBuf power disable timeout\n");
>  
> -	skl_dpll0_disable(dev_priv);
> +	skl_set_cdclk(dev_priv, 24000, 0);

The spec doesn't say how to program CDCLK for the bypass case and we'll
program the 'frequency decimal' field to something isn't listed as a
valid value (and not matching the CD frequency select value). But I
think CDCLK is don't-care in that case, so it's fine.

>  }
>  
>  void skl_init_cdclk(struct drm_i915_private *dev_priv)
>  {
> -	unsigned int cdclk;
> -
>  	/* DPLL0 not enabled (happens on early BIOS versions) */
> -	if (!(I915_READ(LCPLL1_CTL) & LCPLL_PLL_ENABLE)) {
> -		/* enable DPLL0 */
> -		if (dev_priv->skl_vco_freq != 8640)
> -			dev_priv->skl_vco_freq = 8100;
> -		skl_dpll0_enable(dev_priv, dev_priv->skl_vco_freq);
> -		cdclk = skl_calc_cdclk(0, dev_priv->skl_vco_freq);
> -	} else {
> -		cdclk = dev_priv->cdclk_freq;
> -	}
> +	if (dev_priv->skl_vco_freq == 0) {
> +		int cdclk, vco;
>  
> -	/* set CDCLK to the lowest frequency, Modeset follows */
> -	skl_set_cdclk(dev_priv, cdclk);
> +		/* set CDCLK to the lowest frequency, Modeset follows */
> +		vco = 8100;
> +		cdclk = skl_calc_cdclk(0, vco);
> +
> +		skl_set_cdclk(dev_priv, cdclk, vco);
> +	}
>  
>  	/* enable DBUF power */
>  	I915_WRITE(DBUF_CTL, I915_READ(DBUF_CTL) | DBUF_POWER_REQUEST);
> @@ -9777,16 +9785,12 @@ static int skl_modeset_calc_cdclk(struct drm_atomic_state *state)
>  
>  static void skl_modeset_commit_cdclk(struct drm_atomic_state *old_state)

Why is the above called old_state?

The patch looks ok:
Reviewed-by: Imre Deak <imre.deak@intel.com>

>  {
> -	struct drm_device *dev = old_state->dev;
> -	struct drm_i915_private *dev_priv = dev->dev_private;
> -	unsigned int req_cdclk = to_intel_atomic_state(old_state)->dev_cdclk;
> -
> -	/*
> -	 * FIXME disable/enable PLL should wrap set_cdclk()
> -	 */
> -	skl_set_cdclk(dev_priv, req_cdclk);
> +	struct drm_i915_private *dev_priv = to_i915(old_state->dev);
> +	struct intel_atomic_state *intel_state = to_intel_atomic_state(old_state);
> +	unsigned int req_cdclk = intel_state->dev_cdclk;
> +	unsigned int req_vco = intel_state->cdclk_pll_vco;
>  
> -	dev_priv->skl_vco_freq = to_intel_atomic_state(old_state)->cdclk_pll_vco;
> +	skl_set_cdclk(dev_priv, req_cdclk, req_vco);
>  }
>  
>  static int haswell_crtc_compute_clock(struct intel_crtc *crtc,
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