linux-kernel - [PATCH V1 8/9] phy: tegra: p2u: Set ENABLE_L2_EXIT_RATE

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Date:   Mon, 19 Sep 2022 20:06:26 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     <lpieralisi@...nel.org>, <robh@...nel.org>, <kw@...ux.com>,
        <bhelgaas@...gle.com>, <thierry.reding@...il.com>,
        <jonathanh@...dia.com>, <kishon@...com>, <vkoul@...nel.org>,
        <mani@...nel.org>, <Sergey.Semin@...kalelectronics.ru>,
        <ffclaire1224@...il.com>
CC:     <linux-pci@...r.kernel.org>, <linux-tegra@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-phy@...ts.infradead.org>,
        <kthota@...dia.com>, <mmaddireddy@...dia.com>, <vidyas@...dia.com>,
        <sagar.tv@...il.com>
Subject: [PATCH V1 8/9] phy: tegra: p2u: Set ENABLE_L2_EXIT_RATE_CHANGE in calibration

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

ENABLE_L2_EXIT_RATE_CHANGE needs to be set to bring the UPHY PLL rate
back to Gen1 during controller initialization for the link up.

Signed-off-by: Vidya Sagar <vidyas@...dia.com>
---
 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..fb710e89acac 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;
 }
 
+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