Re: [PATCH] drm/i915/dp: Fix the t11_t12 delay for non GEN 9 LP platforms at HW readout and HW write

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

On Wed, Jun 21, 2017 at 12:37:43PM -0700, Manasi Navare wrote:
> According to the eDP spec the minimum value for panel power cycle delay
> (t11_t12) is 500ms and as per the Bspec, PP_DIVISOR panel power cycle
> delay field should be programmed to "+1" value. Eg: To have a delay
> of 500ms this should be programmed to 6. This patch fixes the write
> by adding +1 to the pp_div value so it programs the correct min
> required panel power cycle delay.
> Since we program it to +1 value, when we perform HW readout, this
> value should subtract 1 before verifying pps state. This patch makes
> this correction as well to avoid "PPS state mismatch" error.
> This patch also adds a case where if the readout is 0 for the first readout,
> then read it as 0, dont subtract.
> 
> Signed-off-by: Manasi Navare <manasi.d.navare@intel.com>
> Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
> Cc: Clint Taylor <Clinton.A.Taylor@intel.com>
> ---
>  drivers/gpu/drm/i915/intel_dp.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_dp.c b/drivers/gpu/drm/i915/intel_dp.c
> index bca4ac1..089e373 100644
> --- a/drivers/gpu/drm/i915/intel_dp.c
> +++ b/drivers/gpu/drm/i915/intel_dp.c
> @@ -5149,6 +5149,7 @@ intel_pps_readout_hw_state(struct drm_i915_private *dev_priv,
>  			   struct intel_dp *intel_dp, struct edp_power_seq *seq)
>  {
>  	u32 pp_on, pp_off, pp_div = 0, pp_ctl = 0;
> +	u16 pp_cycle_delay = 0;
>  	struct pps_registers regs;
>  
>  	intel_pps_get_registers(dev_priv, intel_dp, &regs);
> @@ -5177,17 +5178,16 @@ intel_pps_readout_hw_state(struct drm_i915_private *dev_priv,
>  	seq->t10 = (pp_off & PANEL_POWER_DOWN_DELAY_MASK) >>
>  		   PANEL_POWER_DOWN_DELAY_SHIFT;
>  
> -	if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv)) {
> -		u16 tmp = (pp_ctl & BXT_POWER_CYCLE_DELAY_MASK) >>
> +	if (IS_GEN9_LP(dev_priv) || HAS_PCH_CNP(dev_priv))
> +		pp_cycle_delay =  (pp_ctl & BXT_POWER_CYCLE_DELAY_MASK) >>
>  			BXT_POWER_CYCLE_DELAY_SHIFT;
> -		if (tmp > 0)
> -			seq->t11_t12 = (tmp - 1) * 1000;
> -		else
> -			seq->t11_t12 = 0;
> -	} else {
> -		seq->t11_t12 = ((pp_div & PANEL_POWER_CYCLE_DELAY_MASK) >>
> -		       PANEL_POWER_CYCLE_DELAY_SHIFT) * 1000;
> -	}
> +	else
> +		pp_cycle_delay = (pp_div & PANEL_POWER_CYCLE_DELAY_MASK) >>
> +			PANEL_POWER_CYCLE_DELAY_SHIFT;
> +	if (pp_cycle_delay > 0)
> +		seq->t11_t12 = (pp_cycle_delay - 1) * 1000;
> +	else
> +		seq->t11_t12 = 0;

I think it's probably easier to go the other way and just add the +100
msec to the vbt delay, and nuke the BXT/CNP special casing in the code.

>  }
>  
>  static void
> @@ -5341,7 +5341,7 @@ intel_dp_init_panel_power_sequencer_registers(struct drm_device *dev,
>  				<< BXT_POWER_CYCLE_DELAY_SHIFT);
>  	} else {
>  		pp_div = ((100 * div)/2 - 1) << PP_REFERENCE_DIVIDER_SHIFT;
> -		pp_div |= (DIV_ROUND_UP(seq->t11_t12, 1000)
> +		pp_div |= (DIV_ROUND_UP(seq->t11_t12 + 1, 1000)
>  				<< PANEL_POWER_CYCLE_DELAY_SHIFT);
>  	}
>  
> -- 
> 2.1.4

-- 
Ville Syrjälä
Intel OTC
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