Re: [PATCH v2] drm/i915/ltphy: Return true for TBT scenario during lt_phy_state compare

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

On Wed, Feb 04, 2026 at 08:02:47AM +0530, Suraj Kandpal wrote:
> TBT PHY is enablement/disablement is handled by its own TBT module.
> We do not play a big part in it's state management, that being take care
> by it's own TBT modeule.
> The PHY/PLL TypeC mode (TBT, DP-alt) can change after the PLL state was
> computed for a modeset, so the state verification after the modeset
> sequence would indicate a mismatch in case the mode changed from DP-alt
> to TBT, or from TBT to DP-alt mode. To avoid such a mismatch error the
> verification is skipped if the mode for either the read-out or the
> computed state is TBT (where that TBT PLL state doesn't reflect anyway
> the PLL's actual HW state).
> Simply return true when we are in tbt mode.
> 
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>

Reviewed-by: Imre Deak <imre.deak@intel.com>

> ---
> V1 -> V2:
> - Reframe commit messgae with give the full explanation as to why we
> skip verification (Imre)
> 
>  drivers/gpu/drm/i915/display/intel_lt_phy.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy.c b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> index 04f63bdd0b87..27ad8407606b 100644
> --- a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> @@ -2158,6 +2158,9 @@ bool
>  intel_lt_phy_pll_compare_hw_state(const struct intel_lt_phy_pll_state *a,
>  				  const struct intel_lt_phy_pll_state *b)
>  {
> +	if (a->tbt_mode || b->tbt_mode)
> +		return true;
> +
>  	/*
>  	 * With LT PHY values other than VDR0_CONFIG and VDR2_CONFIG are
>  	 * unreliable. They cannot always be read back since internally
> -- 
> 2.34.1
>