Re: [PATCH v4] drm/i915: Apply Display WA #1183 on skl, kbl, and cfl

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Dec 04, 2017 at 03:22:10PM -0800, Lucas De Marchi wrote:
> Display WA #1183 was recently added to workaround
> "Failures when enabling DPLL0 with eDP link rate 2.16
> or 4.32 GHz and CD clock frequency 308.57 or 617.14 MHz
> (CDCLK_CTL CD Frequency Select 10b or 11b) used in this
>  enabling or in previous enabling."
> 
> This workaround was designed to minimize the impact only
> to save the bad case with that link rates. But HW engineers
> indicated that it should be safe to apply broadly, although
> they were expecting the DPLL0 link rate to be unchanged on
> runtime.
> 
> We need to cover 2 cases: when we are in fact enabling DPLL0
> and when we are just changing the frequency with small
> differences.
> 
> This is based on previous patch by Rodrigo Vivi with suggestions
> from Ville Syrjälä.
> 
> Cc: Arthur J Runyan <arthur.j.runyan@intel.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Hmm. This is v4, but it was posted after v5?

You didn't include a changelog in the commit message so I have no idea
what is the difference between these versions. They appear similar on a
first glance.

The changes here *look* correct to me, so
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

But I'm not going to push this right now because I'm too confused about
the version of the patch. I'll be out for a few weeks so if the
confusion is lifted during that time and you want this in please poke
at someone else to push it.

> ---
>  drivers/gpu/drm/i915/i915_reg.h         |  2 ++
>  drivers/gpu/drm/i915/intel_cdclk.c      | 35 ++++++++++++++++++++++++---------
>  drivers/gpu/drm/i915/intel_runtime_pm.c | 10 ++++++++++
>  3 files changed, 38 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 09bf043c1c2e..73335e709ed6 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -7021,6 +7021,7 @@ enum {
>  #define  RESET_PCH_HANDSHAKE_ENABLE	(1<<4)
>  
>  #define GEN8_CHICKEN_DCPR_1		_MMIO(0x46430)
> +#define   SKL_SELECT_ALTERNATE_DC_EXIT	(1<<30)
>  #define   MASK_WAKEMEM			(1<<13)
>  
>  #define SKL_DFSM			_MMIO(0x51000)
> @@ -8575,6 +8576,7 @@ enum skl_power_gate {
>  #define  BXT_CDCLK_CD2X_DIV_SEL_2	(2<<22)
>  #define  BXT_CDCLK_CD2X_DIV_SEL_4	(3<<22)
>  #define  BXT_CDCLK_CD2X_PIPE(pipe)	((pipe)<<20)
> +#define  CDCLK_DIVMUX_CD_OVERRIDE	(1<<19)
>  #define  BXT_CDCLK_CD2X_PIPE_NONE	BXT_CDCLK_CD2X_PIPE(3)
>  #define  BXT_CDCLK_SSA_PRECHARGE_ENABLE	(1<<16)
>  #define  CDCLK_FREQ_DECIMAL_MASK	(0x7ff)
> diff --git a/drivers/gpu/drm/i915/intel_cdclk.c b/drivers/gpu/drm/i915/intel_cdclk.c
> index 9c5ceb98d48f..d77e2bec1e29 100644
> --- a/drivers/gpu/drm/i915/intel_cdclk.c
> +++ b/drivers/gpu/drm/i915/intel_cdclk.c
> @@ -931,16 +931,10 @@ static void skl_set_preferred_cdclk_vco(struct drm_i915_private *dev_priv,
>  
>  static void skl_dpll0_enable(struct drm_i915_private *dev_priv, int vco)
>  {
> -	int min_cdclk = skl_calc_cdclk(0, vco);
>  	u32 val;
>  
>  	WARN_ON(vco != 8100000 && vco != 8640000);
>  
> -	/* select the minimum CDCLK before enabling DPLL 0 */
> -	val = CDCLK_FREQ_337_308 | skl_cdclk_decimal(min_cdclk);
> -	I915_WRITE(CDCLK_CTL, val);
> -	POSTING_READ(CDCLK_CTL);
> -
>  	/*
>  	 * We always enable DPLL0 with the lowest link rate possible, but still
>  	 * taking into account the VCO required to operate the eDP panel at the
> @@ -994,7 +988,7 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv,
>  {
>  	int cdclk = cdclk_state->cdclk;
>  	int vco = cdclk_state->vco;
> -	u32 freq_select;
> +	u32 freq_select, cdclk_ctl;
>  	int ret;
>  
>  	mutex_lock(&dev_priv->pcu_lock);
> @@ -1009,7 +1003,7 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv,
>  		return;
>  	}
>  
> -	/* set CDCLK_CTL */
> +	/* Choose frequency for this cdclk */
>  	switch (cdclk) {
>  	default:
>  		WARN_ON(cdclk != dev_priv->cdclk.hw.ref);
> @@ -1036,10 +1030,33 @@ static void skl_set_cdclk(struct drm_i915_private *dev_priv,
>  	    dev_priv->cdclk.hw.vco != vco)
>  		skl_dpll0_disable(dev_priv);
>  
> +	cdclk_ctl = I915_READ(CDCLK_CTL);
> +
> +	if (dev_priv->cdclk.hw.vco != vco) {
> +		/* Wa Display #1183: skl,kbl,cfl */
> +		cdclk_ctl &= ~(CDCLK_FREQ_SEL_MASK | CDCLK_FREQ_DECIMAL_MASK);
> +		cdclk_ctl |= freq_select | skl_cdclk_decimal(cdclk);
> +		I915_WRITE(CDCLK_CTL, cdclk_ctl);
> +	}
> +
> +	/* Wa Display #1183: skl,kbl,cfl */
> +	cdclk_ctl |= CDCLK_DIVMUX_CD_OVERRIDE;
> +	I915_WRITE(CDCLK_CTL, cdclk_ctl);
> +	POSTING_READ(CDCLK_CTL);
> +
>  	if (dev_priv->cdclk.hw.vco != vco)
>  		skl_dpll0_enable(dev_priv, vco);
>  
> -	I915_WRITE(CDCLK_CTL, freq_select | skl_cdclk_decimal(cdclk));
> +	/* Wa Display #1183: skl,kbl,cfl */
> +	cdclk_ctl &= ~(CDCLK_FREQ_SEL_MASK | CDCLK_FREQ_DECIMAL_MASK);
> +	I915_WRITE(CDCLK_CTL, cdclk_ctl);
> +
> +	cdclk_ctl |= freq_select | skl_cdclk_decimal(cdclk);
> +	I915_WRITE(CDCLK_CTL, cdclk_ctl);
> +
> +	/* Wa Display #1183: skl,kbl,cfl */
> +	cdclk_ctl &= ~CDCLK_DIVMUX_CD_OVERRIDE;
> +	I915_WRITE(CDCLK_CTL, cdclk_ctl);
>  	POSTING_READ(CDCLK_CTL);
>  
>  	/* inform PCU of the change */
> diff --git a/drivers/gpu/drm/i915/intel_runtime_pm.c b/drivers/gpu/drm/i915/intel_runtime_pm.c
> index 8315499452dc..35796fa8e6b4 100644
> --- a/drivers/gpu/drm/i915/intel_runtime_pm.c
> +++ b/drivers/gpu/drm/i915/intel_runtime_pm.c
> @@ -598,6 +598,11 @@ void gen9_enable_dc5(struct drm_i915_private *dev_priv)
>  
>  	DRM_DEBUG_KMS("Enabling DC5\n");
>  
> +	/* Wa Display #1183: skl,kbl,cfl */
> +	if (IS_GEN9_BC(dev_priv))
> +		I915_WRITE(GEN8_CHICKEN_DCPR_1, I915_READ(GEN8_CHICKEN_DCPR_1) |
> +			   SKL_SELECT_ALTERNATE_DC_EXIT);
> +
>  	gen9_set_dc_state(dev_priv, DC_STATE_EN_UPTO_DC5);
>  }
>  
> @@ -625,6 +630,11 @@ void skl_disable_dc6(struct drm_i915_private *dev_priv)
>  {
>  	DRM_DEBUG_KMS("Disabling DC6\n");
>  
> +	/* Wa Display #1183: skl,kbl,cfl */
> +	if (IS_GEN9_BC(dev_priv))
> +		I915_WRITE(GEN8_CHICKEN_DCPR_1, I915_READ(GEN8_CHICKEN_DCPR_1) |
> +			   SKL_SELECT_ALTERNATE_DC_EXIT);
> +
>  	gen9_set_dc_state(dev_priv, DC_STATE_DISABLE);
>  }
>  
> -- 
> 2.14.3

-- 
Ville Syrjälä
Intel OTC