Re: [PATCH 02/17] drm/i915/ddi: Fix HDMI port width programming in DDI_BUF_CTL

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

On Wed, 29 Jan 2025, Imre Deak <imre.deak@intel.com> wrote:
> From: Imre Deak <imre.deak@gmail.com>
>
> Fix the port width programming in the DDI_BUF_CTL register on MTLP+,
> where this had an off-by-one error.

Fixes: b66a8abaa48a ("drm/i915/display/mtl: Fill port width in DDI_BUF_/TRANS_DDI_FUNC_/PORT_BUF_CTL for HDMI")
Cc: <stable@vger.kernel.org> # v6.5+
Reviewed-by: Jani Nikula <jani.nikula@intel.com>

However, if this gets backported, it'll break DSI. Patch 1 needs to
accompany it.

Either add the same Fixes line to patch 1, or squash patches 1-2
together.

>
> Signed-off-by: Imre Deak <imre.deak@gmail.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 2 +-
>  drivers/gpu/drm/i915/i915_reg.h          | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index dc319f37b1be9..36e7dde422d37 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -3501,7 +3501,7 @@ static void intel_ddi_enable_hdmi(struct intel_atomic_state *state,
>  		intel_de_rmw(dev_priv, XELPDP_PORT_BUF_CTL1(dev_priv, port),
>  			     XELPDP_PORT_WIDTH_MASK | XELPDP_PORT_REVERSAL, port_buf);
>  
> -		buf_ctl |= DDI_PORT_WIDTH(lane_count);
> +		buf_ctl |= DDI_PORT_WIDTH(crtc_state->lane_count);
>  
>  		if (DISPLAY_VER(dev_priv) >= 20)
>  			buf_ctl |= XE2LPD_DDI_BUF_D2D_LINK_ENABLE;
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index 03da51b03fb90..04e47d0a8ab92 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -3635,7 +3635,7 @@ enum skl_power_gate {
>  #define  DDI_BUF_IS_IDLE			(1 << 7)
>  #define  DDI_BUF_CTL_TC_PHY_OWNERSHIP		REG_BIT(6)
>  #define  DDI_A_4_LANES				(1 << 4)
> -#define  DDI_PORT_WIDTH(width)			(((width) - 1) << 1)
> +#define  DDI_PORT_WIDTH(width)			(((width) == 3 ? 4 : ((width) - 1)) << 1)
>  #define  DDI_PORT_WIDTH_MASK			(7 << 1)
>  #define  DDI_PORT_WIDTH_SHIFT			1
>  #define  DDI_INIT_DISPLAY_DETECTED		(1 << 0)

-- 
Jani Nikula, Intel