[Intel-gfx] [PATCH 1/2] drm/i915/cnp: Don't touch other PCH clock gating bits.

[Pandiyan, Dhinakaran]

On Fri, 2017-09-08 at 16:45 -0700, Rodrigo Vivi wrote:
> Don't touch other bits. My bad.
> 
> I haven't seen any case where those other bits appeard to be
> set before we touch it, but it is safe to avoid touching
> other bits we weren't told to touch.
> 

Well, I did notice the earlier patch cleared rest of the bits, but we do
the same in ibx_init_clock_gating() and cpt_init_clock_gating() too. So,
I assume it's okay either way and since these bits are for workarounds,
I thought we might as well start by clearing the bits other than those
we know are required. But, since you feel this version is a safer
option, 

Reviewed-by: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>


> Fixes: 0a46ddd57c9e ("drm/i915/cnp: Wa 1181: Fix Backlight issue")
> Cc: Dhinakaran Pandiyan <dhinakaran.pandiyan at intel.com>
> Signed-off-by: Rodrigo Vivi <rodrigo.vivi at intel.com>
> ---
>  drivers/gpu/drm/i915/intel_pm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> index fa9055a4f790..09ecc8e3b2d3 100644
> --- a/drivers/gpu/drm/i915/intel_pm.c
> +++ b/drivers/gpu/drm/i915/intel_pm.c
> @@ -8370,7 +8370,8 @@ static void cnp_init_clock_gating(struct drm_i915_private *dev_priv)
>  		return;
>  
>  	/* Wa #1181 */
> -	I915_WRITE(SOUTH_DSPCLK_GATE_D, CNP_PWM_CGE_GATING_DISABLE);
> +	I915_WRITE(SOUTH_DSPCLK_GATE_D, I915_READ(SOUTH_DSPCLK_GATE_D) |
> +		   CNP_PWM_CGE_GATING_DISABLE);
>  }
>  
>  static void cnl_init_clock_gating(struct drm_i915_private *dev_priv)