[PATCH v1 2/2] phy: mediatek: tphy: Cleanup and document slew calibration

[neil.armstrong at linaro.org]

On 23/06/2025 14:03, AngeloGioacchino Del Regno wrote:
> While it's true that, generally, the T-PHY V3 does not support the
> slew calibration process, some minor versions of it actually do,
> moreover, some SoCs may not support this even though the version
> of the PHY IP does.
> 
> The reference clock and rate coefficient parameters are used only
> for slew calibration: move those to platform data, then document
> and change the checks in hs_slew_rate_calibrate() to perform the
> calibration only if:
>   - EYE value was not supplied (pre-calculated calibration); and
>   - Slew reference clock value is present (not zero); and
>   - Slew coefficient is present (not zero).
> 
> Moreover, change the probe function to always check if both the
> slew reference clock and coefficient properties are present and,
> if not, assign the value from platform data (which, as reminder,
> if not added means that it's zero!), instead of checking the PHY
> IP version.
> 
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno at collabora.com>
> ---
>   drivers/phy/mediatek/phy-mtk-tphy.c | 45 +++++++++++++++++------------
>   1 file changed, 27 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/phy/mediatek/phy-mtk-tphy.c b/drivers/phy/mediatek/phy-mtk-tphy.c
> index 858824b4476e..e5ce1255d735 100644
> --- a/drivers/phy/mediatek/phy-mtk-tphy.c
> +++ b/drivers/phy/mediatek/phy-mtk-tphy.c
> @@ -210,8 +210,6 @@
>   #define P2F_USB_FM_VALID	BIT(0)
>   #define P2F_RG_FRCK_EN		BIT(8)
>   
> -#define U3P_REF_CLK		26	/* MHZ */
> -#define U3P_SLEW_RATE_COEF	28
>   #define U3P_SR_COEF_DIVISOR	1000
>   #define U3P_FM_DET_CYCLE_CNT	1024
>   
> @@ -285,12 +283,16 @@ enum mtk_phy_version {
>    * @sw_efuse_supported:       Switches off eFuse auto-load from PHY and applies values
>    *                            read from different nvmem (usually different eFuse array)
>    *                            that is pointed at in the device tree node for this PHY
> + * @slew_ref_clk_mhz:         Default reference clock (in MHz) for slew rate calibration
> + * @slew_rate_coefficient:    Coefficient for slew rate calibration
>    * @version:                  PHY IP Version
>    */
>   struct mtk_phy_pdata {
>   	bool avoid_rx_sen_degradation;
>   	bool sw_pll_48m_to_26m;
>   	bool sw_efuse_supported;
> +	u8 slew_ref_clock_mhz;
> +	u8 slew_rate_coefficient;
>   	enum mtk_phy_version version;
>   };
>   
> @@ -686,12 +688,14 @@ static void hs_slew_rate_calibrate(struct mtk_tphy *tphy,
>   	int fm_out;
>   	u32 tmp;
>   
> -	/* HW V3 doesn't support slew rate cal anymore */
> -	if (tphy->pdata->version == MTK_PHY_V3)
> -		return;
> -
> -	/* use force value */
> -	if (instance->eye_src)
> +	/*
> +	 * If a fixed HS slew rate (EYE) value was supplied, don't run the
> +	 * calibration sequence and prefer using that value instead; also,
> +	 * if there is no reference clock for slew calibration or there is
> +	 * no slew coefficient, this means that the slew rate calibration
> +	 * sequence is not supported.
> +	 */
> +	if (instance->eye_src || !tphy->src_ref_clk || !tphy->src_coef)
>   		return;
>   
>   	/* enable USB ring oscillator */
> @@ -1516,12 +1520,16 @@ static const struct phy_ops mtk_tphy_ops = {
>   
>   static const struct mtk_phy_pdata tphy_v1_pdata = {
>   	.avoid_rx_sen_degradation = false,
> +	.slew_ref_clock_mhz = 26,
> +	.slew_rate_coefficient = 28,
>   	.version = MTK_PHY_V1,
>   };
>   
>   static const struct mtk_phy_pdata tphy_v2_pdata = {
>   	.avoid_rx_sen_degradation = false,
>   	.sw_efuse_supported = true,
> +	.slew_ref_clock_mhz = 26,
> +	.slew_rate_coefficient = 28,
>   	.version = MTK_PHY_V2,
>   };
>   
> @@ -1532,6 +1540,8 @@ static const struct mtk_phy_pdata tphy_v3_pdata = {
>   
>   static const struct mtk_phy_pdata mt8173_pdata = {
>   	.avoid_rx_sen_degradation = true,
> +	.slew_ref_clock_mhz = 26,
> +	.slew_rate_coefficient = 28,
>   	.version = MTK_PHY_V1,
>   };
>   
> @@ -1561,7 +1571,7 @@ static int mtk_tphy_probe(struct platform_device *pdev)
>   	struct resource *sif_res;
>   	struct mtk_tphy *tphy;
>   	struct resource res;
> -	int port;
> +	int port, ret;
>   
>   	tphy = devm_kzalloc(dev, sizeof(*tphy), GFP_KERNEL);
>   	if (!tphy)
> @@ -1591,15 +1601,14 @@ static int mtk_tphy_probe(struct platform_device *pdev)
>   		}
>   	}
>   
> -	if (tphy->pdata->version < MTK_PHY_V3) {
> -		tphy->src_ref_clk = U3P_REF_CLK;
> -		tphy->src_coef = U3P_SLEW_RATE_COEF;
> -		/* update parameters of slew rate calibrate if exist */
> -		device_property_read_u32(dev, "mediatek,src-ref-clk-mhz",
> -					 &tphy->src_ref_clk);
> -		device_property_read_u32(dev, "mediatek,src-coef",
> -					 &tphy->src_coef);
> -	}
> +	/* Optional properties for slew calibration variation */
> +	ret = device_property_read_u32(dev, "mediatek,src-ref-clk-mhz", &tphy->src_ref_clk);
> +	if (ret)
> +		tphy->src_ref_clk = tphy->pdata->slew_ref_clock_mhz;
> +
> +	ret = device_property_read_u32(dev, "mediatek,src-coef", &tphy->src_coef);
> +	if (ret)
> +		tphy->src_coef = tphy->pdata->slew_rate_coefficient;
>   
>   	port = 0;
>   	for_each_child_of_node_scoped(np, child_np) {

Reviewed-by: Neil Armstrong <neil.armstrong at linaro.org>