phy: qcom-qusb2: Allow specifying default clock scheme

The TCSR's PHY_CLK_SCHEME register is not available on all SoC
models, but some may still use a differential reference clock.

In preparation for these SoCs, add a se_clk_scheme_default
configuration entry and declare it to true for all currently
supported SoCs (retaining the previous defaults.

This patch brings no functional changes.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@somainline.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210114174718.398638-1-angelogioacchino.delregno@somainline.org
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/phy/qualcomm/phy-qcom-qusb2.c

@@ -245,6 +245,9 @@ struct qusb2_phy_cfg {
 
 	/* true if PHY has PLL_CORE_INPUT_OVERRIDE register to reset PLL */
 	bool has_pll_override;
+
+	/* true if PHY default clk scheme is single-ended */
+	bool se_clk_scheme_default;
 };
 
 static const struct qusb2_phy_cfg msm8996_phy_cfg = {
@@ -253,6 +256,7 @@ static const struct qusb2_phy_cfg msm8996_phy_cfg = {
 	.regs		= msm8996_regs_layout,
 
 	.has_pll_test	= true,
+	.se_clk_scheme_default = true,
 	.disable_ctrl	= (CLAMP_N_EN | FREEZIO_N | POWER_DOWN),
 	.mask_core_ready = PLL_LOCKED,
 	.autoresume_en	 = BIT(3),
@@ -266,6 +270,7 @@ static const struct qusb2_phy_cfg msm8998_phy_cfg = {
 	.disable_ctrl   = POWER_DOWN,
 	.mask_core_ready = CORE_READY_STATUS,
 	.has_pll_override = true,
+	.se_clk_scheme_default = true,
 	.autoresume_en   = BIT(0),
 	.update_tune1_with_efuse = true,
 };
@@ -279,6 +284,7 @@ static const struct qusb2_phy_cfg qusb2_v2_phy_cfg = {
 			   POWER_DOWN),
 	.mask_core_ready = CORE_READY_STATUS,
 	.has_pll_override = true,
+	.se_clk_scheme_default = true,
 	.autoresume_en	  = BIT(0),
 	.update_tune1_with_efuse = true,
 };
@@ -701,8 +707,13 @@ static int qusb2_phy_init(struct phy *phy)
 	/* Required to get phy pll lock successfully */
 	usleep_range(150, 160);
 
-	/* Default is single-ended clock on msm8996 */
-	qphy->has_se_clk_scheme = true;
+	/*
+	 * Not all the SoCs have got a readable TCSR_PHY_CLK_SCHEME
+	 * register in the TCSR so, if there's none, use the default
+	 * value hardcoded in the configuration.
+	 */
+	qphy->has_se_clk_scheme = cfg->se_clk_scheme_default;
+
 	/*
 	 * read TCSR_PHY_CLK_SCHEME register to check if single-ended
 	 * clock scheme is selected. If yes, then disable differential