[Intel-gfx] [PATCH 1/2] drm/i915: Program MBUS with rmw during initialization

[Matt Atwood]

On Mon, Feb 03, 2020 at 05:10:31PM -0800, Matt Roper wrote:
> It wasn't terribly clear from the bspec's wording, but after discussion
> with the hardware folks, it turns out that we need to preserve the
> pre-existing contents of the MBUS ABOX control register when
> initializing a few specific bits.
> 
> Bspec: 49213
> Bspec: 50096
> Fixes: 4cb4585e5a7f ("drm/i915/icl: initialize MBus during display init")
> Cc: Stanislav Lisovskiy <stanislav.lisovskiy at intel.com>
Reviewed-by: Matt Atwood <matthew.s.atwood at intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper at intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_display_power.c | 14 +++++++++-----
>  1 file changed, 9 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_display_power.c b/drivers/gpu/drm/i915/display/intel_display_power.c
> index 6d91e180db99..529319c962e8 100644
> --- a/drivers/gpu/drm/i915/display/intel_display_power.c
> +++ b/drivers/gpu/drm/i915/display/intel_display_power.c
> @@ -4504,14 +4504,18 @@ static void icl_dbuf_disable(struct drm_i915_private *dev_priv)
>  
>  static void icl_mbus_init(struct drm_i915_private *dev_priv)
>  {
> -	u32 val;
> +	u32 mask, val;
>  
> +	mask = MBUS_ABOX_BT_CREDIT_POOL1_MASK |
> +		MBUS_ABOX_BT_CREDIT_POOL2_MASK |
> +		MBUS_ABOX_B_CREDIT_MASK |
> +		MBUS_ABOX_BW_CREDIT_MASK;
>  	val = MBUS_ABOX_BT_CREDIT_POOL1(16) |
> -	      MBUS_ABOX_BT_CREDIT_POOL2(16) |
> -	      MBUS_ABOX_B_CREDIT(1) |
> -	      MBUS_ABOX_BW_CREDIT(1);
> +		MBUS_ABOX_BT_CREDIT_POOL2(16) |
> +		MBUS_ABOX_B_CREDIT(1) |
> +		MBUS_ABOX_BW_CREDIT(1);
>  
> -	intel_de_write(dev_priv, MBUS_ABOX_CTL, val);
> +	intel_de_rmw(dev_priv, MBUS_ABOX_CTL, mask, val);
>  }
>  
>  static void hsw_assert_cdclk(struct drm_i915_private *dev_priv)
> -- 
> 2.24.1
> 
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