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@xxxxxx>
Signed-off-by: Gabriel Fernandez <gabriel.fernandez@xxxxxxxxxx>
---
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
--
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