Re: [PATCH 3/3] drm/i915/ltphy: Provide protection against unsupported modes

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 12/31/2025 10:53 AM, Suraj Kandpal wrote:
> We need to make sure we return some port clock in case we have
> unsupported LT PHY modes or if we were not able to read the LT PHY state
> for whatever reason and the mode ends up being 0.
>
> Signed-off-by: Suraj Kandpal <suraj.kandpal@intel.com>

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>


> ---
>   drivers/gpu/drm/i915/display/intel_lt_phy.c | 7 ++++++-
>   1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/display/intel_lt_phy.c b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> index cc85818c2b7e..54d1c68cf83a 100644
> --- a/drivers/gpu/drm/i915/display/intel_lt_phy.c
> +++ b/drivers/gpu/drm/i915/display/intel_lt_phy.c
> @@ -31,6 +31,7 @@
>   #define INTEL_LT_PHY_BOTH_LANES		(INTEL_LT_PHY_LANE1 |\
>   					 INTEL_LT_PHY_LANE0)
>   #define MODE_DP				3
> +#define MODE_HDMI_20			4
>   #define Q32_TO_INT(x)	((x) >> 32)
>   #define Q32_TO_FRAC(x)	((x) & 0xFFFFFFFF)
>   #define DCO_MIN_FREQ_MHZ	11850
> @@ -1751,6 +1752,7 @@ int
>   intel_lt_phy_calc_port_clock(struct intel_encoder *encoder,
>   			     const struct intel_crtc_state *crtc_state)
>   {
> +	struct intel_display *display = to_intel_display(encoder);
>   	int clk;
>   	const struct intel_lt_phy_pll_state *lt_state =
>   		&crtc_state->dpll_hw_state.ltpll;
> @@ -1768,8 +1770,11 @@ intel_lt_phy_calc_port_clock(struct intel_encoder *encoder,
>   		rate = REG_FIELD_GET8(LT_PHY_VDR_RATE_ENCODING_MASK,
>   				      lt_state->config[0]);
>   		clk = intel_lt_phy_get_dp_clock(rate);
> -	} else {
> +	} else if (mode == MODE_HDMI_20) {
>   		clk = intel_lt_phy_calc_hdmi_port_clock(crtc_state);
> +	} else {
> +		drm_WARN_ON(display->drm, "Unsupported LT PHY Mode!\n");
> +		clk = xe3plpd_lt_hdmi_252.clock;
>   	}
>   
>   	return clk;