phy: miphy28lp: Add SSC support for SATA

This patch to tune on/off the ssc on miphy sata setup.
User can now enable ssc via dt blob, it is useful to reduce
effects of EMI.
Signed-off-by: Giuseppe Condorelli <giuseppe.condorelli@st.com>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@linaro.org>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>

Documentation/devicetree/bindings/phy/phy-miphy28lp.txt

@@ -39,6 +39,7 @@ Optional properties (port (child) node):
 			  register.
 - st,px_rx_pol_inv	: to invert polarity of RXn/RXp (respectively negative line and positive
 			  line).
+- st,scc-on		: enable ssc to reduce effects of EMI (only for sata or PCIe).
 
 example:
 

drivers/phy/phy-miphy28lp.c

@@ -191,6 +191,8 @@
 #define SYSCFG_PCIE_PCIE_VAL	0x80
 #define SATA_SPDMODE		1
 
+#define MIPHY_SATA_BANK_NB	3
+
 struct miphy28lp_phy {
 	struct phy *phy;
 	struct miphy28lp_dev *phydev;
@@ -200,6 +202,7 @@ struct miphy28lp_phy {
 	bool osc_force_ext;
 	bool osc_rdy;
 	bool px_rx_pol_inv;
+	bool ssc;
 
 	struct reset_control *miphy_rst;
 
@@ -550,6 +553,44 @@ static inline void miphy28_usb3_miphy_reset(struct miphy28lp_phy *miphy_phy)
 	writeb_relaxed(0x00, base + MIPHY_CONF);
 }
 
+static void miphy_sata_tune_ssc(struct miphy28lp_phy *miphy_phy)
+{
+	void __iomem *base = miphy_phy->base;
+	u8 val;
+
+	/* Compensate Tx impedance to avoid out of range values */
+	/*
+	 * Enable the SSC on PLL for all banks
+	 * SSC Modulation @ 31 KHz and 4000 ppm modulation amp
+	 */
+	val = readb_relaxed(base + MIPHY_BOUNDARY_2);
+	val |= SSC_EN_SW;
+	writeb_relaxed(val, base + MIPHY_BOUNDARY_2);
+
+	val = readb_relaxed(base + MIPHY_BOUNDARY_SEL);
+	val |= SSC_SEL;
+	writeb_relaxed(val, base + MIPHY_BOUNDARY_SEL);
+
+	for (val = 0; val < MIPHY_SATA_BANK_NB; val++) {
+		writeb_relaxed(val, base + MIPHY_CONF);
+
+		/* Add value to each reference clock cycle  */
+		/* and define the period length of the SSC */
+		writeb_relaxed(0x3c, base + MIPHY_PLL_SBR_2);
+		writeb_relaxed(0x6c, base + MIPHY_PLL_SBR_3);
+		writeb_relaxed(0x81, base + MIPHY_PLL_SBR_4);
+
+		/* Clear any previous request */
+		writeb_relaxed(0x00, base + MIPHY_PLL_SBR_1);
+
+		/* requests the PLL to take in account new parameters */
+		writeb_relaxed(SET_NEW_CHANGE, base + MIPHY_PLL_SBR_1);
+
+		/* To be sure there is no other pending requests */
+		writeb_relaxed(0x00, base + MIPHY_PLL_SBR_1);
+	}
+}
+
 static inline int miphy28lp_configure_sata(struct miphy28lp_phy *miphy_phy)
 {
 	void __iomem *base = miphy_phy->base;
@@ -585,6 +626,9 @@ static inline int miphy28lp_configure_sata(struct miphy28lp_phy *miphy_phy)
 		writeb_relaxed(val, miphy_phy->base + MIPHY_CONTROL);
 	}
 
+	if (miphy_phy->ssc)
+		miphy_sata_tune_ssc(miphy_phy);
+
 	return 0;
 }
 
@@ -1064,6 +1108,8 @@ static int miphy28lp_of_probe(struct device_node *np,
 	miphy_phy->px_rx_pol_inv =
 		of_property_read_bool(np, "st,px_rx_pol_inv");
 
+	miphy_phy->ssc = of_property_read_bool(np, "st,ssc-on");
+
 	of_property_read_u32(np, "st,sata-gen", &miphy_phy->sata_gen);
 	if (!miphy_phy->sata_gen)
 		miphy_phy->sata_gen = SATA_GEN1;