Re: [Intel-gfx] [PATCH 16/16] drm/i915: Fix icl+ combo phy static lane power down setup

[Jani Nikula <jani.nikula@linux.intel.com>]

On Wed, 06 Oct 2021, Ville Syrjala <ville.syrjala@linux.intel.com> wrote:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> Our lane power down defines already include the necessary shift,
> don't shit them a second time.

*chuckle*

>
> Fortunately we masked off the correct bits, so we accidentally
> left all lanes powered up all the time.
>
> Bits 8-11 where we end up writing our misdirected lane mask are
> documented as MBZ, but looks like you can actually write there
> so they're not read only bits. No idea what side effect the
> bogus register write might have.
>
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/4151
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_combo_phy.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_combo_phy.c b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> index 634e8d449457..f628e0542933 100644
> --- a/drivers/gpu/drm/i915/display/intel_combo_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_combo_phy.c
> @@ -301,7 +301,7 @@ void intel_combo_phy_power_up_lanes(struct drm_i915_private *dev_priv,
>  
>  	val = intel_de_read(dev_priv, ICL_PORT_CL_DW10(phy));
>  	val &= ~PWR_DOWN_LN_MASK;
> -	val |= lane_mask << PWR_DOWN_LN_SHIFT;
> +	val |= lane_mask;
>  	intel_de_write(dev_priv, ICL_PORT_CL_DW10(phy), val);
>  }

-- 
Jani Nikula, Intel Open Source Graphics Center