phy: rockchip-snps-pcie3: add support for rockchip,rx-common-refclk-mode

>From the RK3588 Technical Reference Manual, Part1,
section 6.19 PCIe3PHY_GRF Register Description:
"rxX_cmn_refclk_mode"
RX common reference clock mode for lane X. This mode should be enabled
only when the far-end and near-end devices are running with a common
reference clock.

The hardware reset value for this field is 0x1 (enabled).
Note that this register field is only available on RK3588, not on RK3568.

The link training either fails or is highly unstable (link state will jump
continuously between L0 and recovery) when this mode is enabled while
using an endpoint running in Separate Reference Clock with No SSC (SRNS)
mode or Separate Reference Clock with SSC (SRIS) mode.
(Which is usually the case when using a real SoC as endpoint, e.g. the
RK3588 PCIe controller can run in both Root Complex and Endpoint mode.)

Add support for the device tree property rockchip,rx-common-refclk-mode,
such that the PCIe PHY can be used in configurations where the Root
Complex and Endpoint are not using a common reference clock.

Signed-off-by: Niklas Cassel <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Vinod Koul <[email protected]>

Author: floatious

drivers/phy/rockchip/phy-rockchip-snps-pcie3.c

@@ -35,11 +35,17 @@
 #define RK3588_PCIE3PHY_GRF_CMN_CON0		0x0
 #define RK3588_PCIE3PHY_GRF_PHY0_STATUS1	0x904
 #define RK3588_PCIE3PHY_GRF_PHY1_STATUS1	0xa04
+#define RK3588_PCIE3PHY_GRF_PHY0_LN0_CON1	0x1004
+#define RK3588_PCIE3PHY_GRF_PHY0_LN1_CON1	0x1104
+#define RK3588_PCIE3PHY_GRF_PHY1_LN0_CON1	0x2004
+#define RK3588_PCIE3PHY_GRF_PHY1_LN1_CON1	0x2104
 #define RK3588_SRAM_INIT_DONE(reg)		(reg & BIT(0))
 
 #define RK3588_BIFURCATION_LANE_0_1		BIT(0)
 #define RK3588_BIFURCATION_LANE_2_3		BIT(1)
 #define RK3588_LANE_AGGREGATION		BIT(2)
+#define RK3588_RX_CMN_REFCLK_MODE_EN		((BIT(7) << 16) |  BIT(7))
+#define RK3588_RX_CMN_REFCLK_MODE_DIS		(BIT(7) << 16)
 #define RK3588_PCIE1LN_SEL_EN			(GENMASK(1, 0) << 16)
 #define RK3588_PCIE30_PHY_MODE_EN		(GENMASK(2, 0) << 16)
 
@@ -60,6 +66,7 @@ struct rockchip_p3phy_priv {
 	int num_clks;
 	int num_lanes;
 	u32 lanes[4];
+	u32 rx_cmn_refclk_mode[4];
 };
 
 struct rockchip_p3phy_ops {
@@ -137,6 +144,19 @@ static int rockchip_p3phy_rk3588_init(struct rockchip_p3phy_priv *priv)
 	u8 mode = RK3588_LANE_AGGREGATION; /* default */
 	int ret;
 
+	regmap_write(priv->phy_grf, RK3588_PCIE3PHY_GRF_PHY0_LN0_CON1,
+		     priv->rx_cmn_refclk_mode[0] ? RK3588_RX_CMN_REFCLK_MODE_EN :
+		     RK3588_RX_CMN_REFCLK_MODE_DIS);
+	regmap_write(priv->phy_grf, RK3588_PCIE3PHY_GRF_PHY0_LN1_CON1,
+		     priv->rx_cmn_refclk_mode[1] ? RK3588_RX_CMN_REFCLK_MODE_EN :
+		     RK3588_RX_CMN_REFCLK_MODE_DIS);
+	regmap_write(priv->phy_grf, RK3588_PCIE3PHY_GRF_PHY1_LN0_CON1,
+		     priv->rx_cmn_refclk_mode[2] ? RK3588_RX_CMN_REFCLK_MODE_EN :
+		     RK3588_RX_CMN_REFCLK_MODE_DIS);
+	regmap_write(priv->phy_grf, RK3588_PCIE3PHY_GRF_PHY1_LN1_CON1,
+		     priv->rx_cmn_refclk_mode[3] ? RK3588_RX_CMN_REFCLK_MODE_EN :
+		     RK3588_RX_CMN_REFCLK_MODE_DIS);
+
 	/* Deassert PCIe PMA output clamp mode */
 	regmap_write(priv->phy_grf, RK3588_PCIE3PHY_GRF_CMN_CON0, BIT(8) | BIT(24));
 
@@ -275,6 +295,23 @@ static int rockchip_p3phy_probe(struct platform_device *pdev)
 		return priv->num_lanes;
 	}
 
+	ret = of_property_read_variable_u32_array(dev->of_node,
+						  "rockchip,rx-common-refclk-mode",
+						  priv->rx_cmn_refclk_mode, 1,
+						  ARRAY_SIZE(priv->rx_cmn_refclk_mode));
+	/*
+	 * if no rockchip,rx-common-refclk-mode, assume enabled for all lanes in
+	 * order to be DT backwards compatible. (Since HW reset val is enabled.)
+	 */
+	if (ret == -EINVAL) {
+		for (int i = 0; i < ARRAY_SIZE(priv->rx_cmn_refclk_mode); i++)
+			priv->rx_cmn_refclk_mode[i] = 1;
+	} else if (ret < 0) {
+		dev_err(dev, "failed to read rockchip,rx-common-refclk-mode property %d\n",
+			ret);
+		return ret;
+	}
+
 	priv->phy = devm_phy_create(dev, NULL, &rockchip_p3phy_ops);
 	if (IS_ERR(priv->phy)) {
 		dev_err(dev, "failed to create combphy\n");