[PATCH v4 6/8] phy: miphy28lp: Add SSC support for PCIE

[Gabriel FERNANDEZ]

SSC is the technique of modulating the operating frequency of a signal
slightly to spread its radiated emissions over a range of frequencies.
This reduction in the maximum emission for a given frequency helps meet
radiated emission requirements.
These settings are applicable for PCIE with Internal clock.

Signed-off-by: Harsh Gupta <harsh.gupta at st.com>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez at linaro.org>
---
 drivers/phy/phy-miphy28lp.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/drivers/phy/phy-miphy28lp.c b/drivers/phy/phy-miphy28lp.c
index d4569af..ca0d9b4 100644
--- a/drivers/phy/phy-miphy28lp.c
+++ b/drivers/phy/phy-miphy28lp.c
@@ -192,6 +192,7 @@
 #define SATA_SPDMODE		1
 
 #define MIPHY_SATA_BANK_NB	3
+#define MIPHY_PCIE_BANK_NB	2
 
 struct miphy28lp_phy {
 	struct phy *phy;
@@ -591,6 +592,46 @@ static void miphy_sata_tune_ssc(struct miphy28lp_phy *miphy_phy)
 	}
 }
 
+static void miphy_pcie_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_PCIE_BANK_NB; val++) {
+		writeb_relaxed(val, base + MIPHY_CONF);
+
+		/* Validate Step component */
+		writeb_relaxed(0x69, base + MIPHY_PLL_SBR_3);
+		writeb_relaxed(0x21, base + MIPHY_PLL_SBR_4);
+
+		/* Validate Period component */
+		writeb_relaxed(0x3c, base + MIPHY_PLL_SBR_2);
+		writeb_relaxed(0x21, 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;
@@ -659,6 +700,9 @@ static inline int miphy28lp_configure_pcie(struct miphy28lp_phy *miphy_phy)
 	if (err)
 		return err;
 
+	if (miphy_phy->ssc)
+		miphy_pcie_tune_ssc(miphy_phy);
+
 	return 0;
 }
 
-- 
1.9.1