Re: [Intel-gfx] [PATCH 1/1] drm/i915/display: HDMI2.0/DP1p62Gbps skew violation when there is skew between DL PCLK

[Imre Deak <imre.deak@intel.com>]

On Tue, Jun 27, 2023 at 09:04:51PM +0530, Mitul Golani wrote:
> When doing type-C PHY voltage swing programming for HDMI and
> DP 1.62Gbps, program DKLP_PCS_GLUE_TX_DPCNTL2[loadgen_sharing_pmd_disable]
> to '1'. For other DP frequencies, program
> DKLP_PCS_GLUE_TX_DPCNTL2[loadgen_sharing_pmd_disable] to '0'.
> 
> This Workaround is specific to Display Version 13
> 
> Wa_15010727533
> 
> Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
> ---
>  drivers/gpu/drm/i915/display/intel_ddi.c | 13 +++++++++++++
>  drivers/gpu/drm/i915/i915_reg.h          |  6 ++++++
>  2 files changed, 19 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_ddi.c b/drivers/gpu/drm/i915/display/intel_ddi.c
> index 61722556bb47..5a6f048f4f1c 100644
> --- a/drivers/gpu/drm/i915/display/intel_ddi.c
> +++ b/drivers/gpu/drm/i915/display/intel_ddi.c
> @@ -1362,6 +1362,19 @@ static void tgl_dkl_phy_set_signal_levels(struct intel_encoder *encoder,
>  		intel_dkl_phy_rmw(dev_priv, DKL_TX_DPCNTL2(tc_port, ln),
>  				  DKL_TX_DP20BITMODE, 0);
>  
> +		if (DISPLAY_VER(dev_priv) == 13) {

The above check here is equivalent to IS_ALDERLAKE_P(), so the
programming should be done under that condition below, along with the
other bits in DKL_TX_DPCNTL2.

Also the WA is limited to STEP_A0 .. STEP_C0.

> +			if ((crtc_state->port_clock == 594000 &&
> +			    intel_crtc_has_type(crtc_state, INTEL_OUTPUT_HDMI)) ||
> +			    (crtc_state->port_clock == 162000 &&
> +			    intel_crtc_has_type(crtc_state, INTEL_OUTPUT_DP))) {
> +				intel_de_rmw(dev_priv, DKLP_TX_DPCNTL2(tc_port),
> +					     LOADGEN_SHARING_PMD_DISABLE, 1);

Must use intel_dkl_phy_rmw() with DKL regs.

> +			} else {
> +				intel_de_rmw(dev_priv, DKLP_TX_DPCNTL2(tc_port),
> +					     LOADGEN_SHARING_PMD_DISABLE, 0);
> +			}
> +		}
> +
>  		if (IS_ALDERLAKE_P(dev_priv)) {
>  			u32 val;
>  
> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
> index dcf64e32cd54..5487301d4ad3 100644
> --- a/drivers/gpu/drm/i915/i915_reg.h
> +++ b/drivers/gpu/drm/i915/i915_reg.h
> @@ -6663,4 +6663,10 @@ enum skl_power_gate {
>  
>  #define MTL_MEDIA_GSI_BASE		0x380000
>  
> +#define _DKLP_PCS_GLUE_TX_DPCNTL2	0xB68

These registers are defined in intel_dkl_phy_regs.h.

Not sure about the above offset. There's been updates to the spec and I
think the last known good value is 0x02c8 defined at

Bspec 49295

That is just the already defined DKL_TX_DPCNTL2.

> +#define LOADGEN_SHARING_PMD_DISABLE	REG_BIT(2)

This doesn't seem to match either bspec 55359, where bit 2 is
cfg_dp20bitmode and bit 12 is loadgen_sharing_pmd_disable.

> +#define DKLP_TX_DPCNTL2(tc_port)	_MMIO(_PORT(tc_port, \
> +						    _DKL_PHY1_BASE, \
> +						    _DKL_PHY2_BASE) + \
> +						    _DKLP_PCS_GLUE_TX_DPCNTL2)
>  #endif /* _I915_REG_H_ */
> -- 
> 2.25.1
>