[PATCH V3 08/21] phy: tegra: p2u: Set ENABLE_L2_EXIT_RATE_CHANGE in calibration

[Vidya Sagar <vidyas@nvidia.com>]

Set ENABLE_L2_EXIT_RATE_CHANGE register bit to request UPHY PLL rate change
to Gen1 during initialization. This helps in the below surprise link down
cases,
  - Surprise link down happens at Gen3/Gen4 link speed.
  - Surprise link down happens and external REFCLK is cut off, which causes
UPHY PLL rate to deviate to an invalid rate.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
---
V3:
* Removed "Reported-by: kernel test robot <lkp@intel.com>" based on Bjorn's review comment
* Reworded the commit message

V2:
* Addressed review comment from test bot and Vinod

 drivers/phy/tegra/phy-tegra194-p2u.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/phy/tegra/phy-tegra194-p2u.c b/drivers/phy/tegra/phy-tegra194-p2u.c
index 1415ca71de38..633e6b747275 100644
--- a/drivers/phy/tegra/phy-tegra194-p2u.c
+++ b/drivers/phy/tegra/phy-tegra194-p2u.c
@@ -15,6 +15,7 @@
 #include <linux/phy/phy.h>
 
 #define P2U_CONTROL_CMN			0x74
+#define P2U_CONTROL_CMN_ENABLE_L2_EXIT_RATE_CHANGE		BIT(13)
 #define P2U_CONTROL_CMN_SKP_SIZE_PROTECTION_EN			BIT(20)
 
 #define P2U_PERIODIC_EQ_CTRL_GEN3	0xc0
@@ -85,8 +86,21 @@ static int tegra_p2u_power_on(struct phy *x)
 	return 0;
 }
 
+static int tegra_p2u_calibrate(struct phy *x)
+{
+	struct tegra_p2u *phy = phy_get_drvdata(x);
+	u32 val;
+
+	val = p2u_readl(phy, P2U_CONTROL_CMN);
+	val |= P2U_CONTROL_CMN_ENABLE_L2_EXIT_RATE_CHANGE;
+	p2u_writel(phy, val, P2U_CONTROL_CMN);
+
+	return 0;
+}
+
 static const struct phy_ops ops = {
 	.power_on = tegra_p2u_power_on,
+	.calibrate = tegra_p2u_calibrate,
 	.owner = THIS_MODULE,
 };
 
-- 
2.17.1