[PATCH V2 03/12] PCI: tegra: Retrain link for Gen2 speed

[Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>]

Tegra124, 132, 210 and 186 supports Gen2 link speed. After the link is up
in Gen1, set target link speed as Gen2 and retrain link. Link switches to
Gen2 speed if Gen2 capable end point is connected, else link stays in Gen1.

Signed-off-by: Manikanta Maddireddy <mmaddireddy@xxxxxxxxxx>
---
V2:
* Fixed alignment issue

 drivers/pci/host/pci-tegra.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/drivers/pci/host/pci-tegra.c b/drivers/pci/host/pci-tegra.c
index 2c64eb6cc3cc..9f6d331c3571 100644
--- a/drivers/pci/host/pci-tegra.c
+++ b/drivers/pci/host/pci-tegra.c
@@ -232,6 +232,8 @@
 #define PADS_REFCLK_CFG_PREDI_SHIFT		8  /* 11:8 */
 #define PADS_REFCLK_CFG_DRVI_SHIFT		12 /* 15:12 */
 
+#define LINK_RETRAIN_TIMEOUT HZ
+
 struct tegra_msi {
 	struct msi_controller chip;
 	DECLARE_BITMAP(used, INT_PCI_MSI_NR);
@@ -2133,6 +2135,42 @@ static void tegra_pcie_enable_ports(struct tegra_pcie *pcie)
 	}
 }
 
+static void tegra_pcie_change_link_speed(struct tegra_pcie *pcie,
+					 struct pci_dev *pci_dev)
+{
+	struct device *dev = pcie->dev;
+	unsigned long start_jiffies;
+	unsigned short val;
+
+	/* Skip if the current device is not a root port */
+	if (pci_pcie_type(pci_dev) != PCI_EXP_TYPE_ROOT_PORT)
+		return;
+
+	pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL2, &val);
+	val &= ~PCI_EXP_LNKSTA_CLS;
+	val |= PCI_EXP_LNKSTA_CLS_5_0GB;
+	pcie_capability_write_word(pci_dev, PCI_EXP_LNKCTL2, val);
+
+	/* Retrain the link */
+	pcie_capability_read_word(pci_dev, PCI_EXP_LNKCTL, &val);
+	val |= PCI_EXP_LNKCTL_RL;
+	pcie_capability_write_word(pci_dev, PCI_EXP_LNKCTL, val);
+
+	start_jiffies = jiffies;
+	for (;;) {
+		pcie_capability_read_word(pci_dev, PCI_EXP_LNKSTA, &val);
+		if (!(val & PCI_EXP_LNKSTA_LT))
+			break;
+		if (time_after(jiffies, start_jiffies + LINK_RETRAIN_TIMEOUT))
+			break;
+		usleep_range(2000, 3000);
+	}
+
+	if (val & PCI_EXP_LNKSTA_LT)
+		dev_err(dev, "link retrain of PCIe slot %u failed\n",
+			PCI_SLOT(pci_dev->devfn));
+}
+
 static const struct tegra_pcie_soc tegra20_pcie = {
 	.num_ports = 2,
 	.msi_base_shift = 0,
@@ -2334,6 +2372,7 @@ static int tegra_pcie_probe(struct platform_device *pdev)
 	struct pci_host_bridge *host;
 	struct tegra_pcie *pcie;
 	struct pci_bus *child;
+	struct pci_dev *pci_dev = NULL;
 	int err;
 
 	host = devm_pci_alloc_host_bridge(dev, sizeof(*pcie));
@@ -2399,6 +2438,9 @@ static int tegra_pcie_probe(struct platform_device *pdev)
 
 	pci_bus_add_devices(host->bus);
 
+	for_each_pci_dev(pci_dev)
+		tegra_pcie_change_link_speed(pcie, pci_dev);
+
 	if (IS_ENABLED(CONFIG_DEBUG_FS)) {
 		err = tegra_pcie_debugfs_init(pcie);
 		if (err < 0)
-- 
2.1.4