linux-kernel - [RFC PATCH v3 2/3] PCI: rockchip-host: Retry link training on failure without PERST#

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Message-ID: <b7c09279b4a7dbdba92543db9b9af169776bd90c.1749582046.git.geraldogabriel@gmail.com>
Date: Tue, 10 Jun 2025 16:05:40 -0300
From: Geraldo Nascimento <geraldogabriel@...il.com>
To: linux-rockchip@...ts.infradead.org
Cc: Hugh Cole-Baker <sigmaris@...il.com>,
	Shawn Lin <shawn.lin@...k-chips.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kw@...ux.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
	Rob Herring <robh@...nel.org>, Bjorn Helgaas <bhelgaas@...gle.com>,
	Heiko Stuebner <heiko@...ech.de>, linux-pci@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v3 2/3] PCI: rockchip-host: Retry link training on
 failure without PERST#

After almost 30 days of battling with RK3399 buggy PCIe on my Rock Pi
N10 through trial-and-error debugging, I finally got positive results
with enumeration on the PCI bus for both a Realtek 8111E NIC and a
Samsung PM981a SSD.

The NIC was connected to a M.2->PCIe x4 riser card and it would get
stuck on Polling.Compliance, without breaking electrical idle on the
Host RX side. The Samsung PM981a SSD is directly connected to M.2
connector and that SSD is known to be quirky (OEM... no support)
and non-functional on the RK3399 platform.

The Samsung SSD was even worse than the NIC - it would get stuck on
Detect.Active like a bricked card, even though it was fully functional
via USB adapter.

It seems both devices benefit from retrying Link Training if - big if
here - PERST# is not toggled during retry.

For retry to work, flow must be exactly as handled by present patch,
that is, we must cut power, disable the clocks, then re-enable
both clocks and power regulators and go through initialization
without touching PERST#. Then quirky devices are able to sucessfully
enumerate.

No functional change intended for already working devices.

Signed-off-by: Geraldo Nascimento <geraldogabriel@...il.com>
---
 drivers/pci/controller/pcie-rockchip-host.c | 47 ++++++++++++++++++---
 1 file changed, 40 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index 2a1071cd3241..67b3b379d277 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -338,11 +338,14 @@ static int rockchip_pcie_set_vpcie(struct rockchip_pcie *rockchip)
 static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 {
 	struct device *dev = rockchip->dev;
-	int err, i = MAX_LANE_NUM;
+	int err, i = MAX_LANE_NUM, is_reinit = 0;
 	u32 status;
 
-	gpiod_set_value_cansleep(rockchip->perst_gpio, 0);
+	if (!is_reinit) {
+		gpiod_set_value_cansleep(rockchip->perst_gpio, 0);
+	}
 
+reinit:
 	err = rockchip_pcie_init_port(rockchip);
 	if (err)
 		return err;
@@ -369,16 +372,46 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 	rockchip_pcie_write(rockchip, PCIE_CLIENT_LINK_TRAIN_ENABLE,
 			    PCIE_CLIENT_CONFIG);
 
-	msleep(PCIE_T_PVPERL_MS);
-	gpiod_set_value_cansleep(rockchip->perst_gpio, 1);
-
-	msleep(PCIE_T_RRS_READY_MS);
+	if (!is_reinit) {
+		msleep(PCIE_T_PVPERL_MS);
+		gpiod_set_value_cansleep(rockchip->perst_gpio, 1);
+		msleep(PCIE_T_RRS_READY_MS);
+	}
 
 	/* 500ms timeout value should be enough for Gen1/2 training */
 	err = readl_poll_timeout(rockchip->apb_base + PCIE_CLIENT_BASIC_STATUS1,
 				 status, PCIE_LINK_UP(status), 20,
 				 500 * USEC_PER_MSEC);
-	if (err) {
+
+	if (err && !is_reinit) {
+		while (i--)
+			phy_power_off(rockchip->phys[i]);
+		i = MAX_LANE_NUM;
+		while (i--)
+			phy_exit(rockchip->phys[i]);
+		i = MAX_LANE_NUM;
+		is_reinit = 1;
+		dev_dbg(dev, "Will reinit PCIe without toggling PERST#");
+		if (!IS_ERR(rockchip->vpcie12v))
+			regulator_disable(rockchip->vpcie12v);
+		if (!IS_ERR(rockchip->vpcie3v3))
+			regulator_disable(rockchip->vpcie3v3);
+		regulator_disable(rockchip->vpcie1v8);
+		regulator_disable(rockchip->vpcie0v9);
+		rockchip_pcie_disable_clocks(rockchip);
+		err = rockchip_pcie_enable_clocks(rockchip);
+		if (err)
+			return err;
+		err = rockchip_pcie_set_vpcie(rockchip);
+		if (err) {
+			dev_err(dev, "failed to set vpcie regulator\n");
+			rockchip_pcie_disable_clocks(rockchip);
+			return err;
+		}
+		goto reinit;
+	}
+
+	else if (err) {
 		dev_err(dev, "PCIe link training gen1 timeout!\n");
 		goto err_power_off_phy;
 	}
-- 
2.49.0