FAILED: patch "[PATCH] PCI: rockchip-host: Do not attempt 5.0 GT/s retraining" failed to apply to 5.15-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y
git checkout FETCH_HEAD
git cherry-pick -x 2a1e6c382fb7567679c07bd6a7060fefc7a5edc9
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261107060534-failed-5.15-2a1e6c382fb7@kernel.org' --subject-prefix 'PATCH 5.15.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 2a1e6c382fb7567679c07bd6a7060fefc7a5edc9 Mon Sep 17 00:00:00 2001
From: Geraldo Nascimento <geraldogabriel@gmail.com>
Date: Tue, 16 Jun 2026 12:25:45 -0300
Subject: [PATCH] PCI: rockchip-host: Do not attempt 5.0 GT/s retraining

Drop the 5.0 GT/s Link Speed retraining from Rockchip PCIe Root Complex
Mode Operation, so-called host driver.

The reason is that Shawn Lin from Rockchip has reiterated that there may be
danger of "catastrophic failure" in using their PCIe with 5.0GT/s speeds.

While Rockchip has done so informally without issuing a proper errata, and
the particulars are thus unknown, this may cause data loss or worse.

This change is corroborated by RK3399 official datasheet [1], which states
maximum link speed for this platform is 2.5 GT/s.

[1] https://opensource.rock-chips.com/images/d/d7/Rockchip_RK3399_Datasheet_V2.1-20200323.pdf

Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support")
Reported-by: Dragan Simic <dsimic@manjaro.org>
Reported-by: Shawn Lin <shawn.lin@rock-chips.com>
Link: https://lore.kernel.org/all/ffd05070-9879-4468-94e3-b88968b4c21b@rock-chips.com/
Signed-off-by: Geraldo Nascimento <geraldogabriel@gmail.com>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Reviewed-by: Shawn Lin <shawn.lin@rock-chips.com>
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/68f6353e3a2ea4914de36c42b6906e41282adad3.1781622998.git.geraldogabriel@gmail.com
---
 drivers/pci/controller/pcie-rockchip-host.c | 20 --------------------
 1 file changed, 20 deletions(-)

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index d203c4876d304..0b52f2e370f41 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -328,26 +328,6 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 		goto err_power_off_phy;
 	}
 
-	if (rockchip->link_gen == 2) {
-		/*
-		 * Enable retrain for gen2. This should be configured only after
-		 * gen1 finished.
-		 */
-		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
-		status &= ~PCI_EXP_LNKCTL2_TLS;
-		status |= PCI_EXP_LNKCTL2_TLS_5_0GT;
-		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
-		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL);
-		status |= PCI_EXP_LNKCTL_RL;
-		rockchip_pcie_write(rockchip, status, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL);
-
-		err = readl_poll_timeout(rockchip->apb_base + PCIE_CORE_CTRL,
-					 status, PCIE_LINK_IS_GEN2(status), 20,
-					 500 * USEC_PER_MSEC);
-		if (err)
-			dev_dbg(dev, "PCIe link training gen2 timeout, fall back to gen1!\n");
-	}
-
 	/* Check the final link width from negotiated lane counter from MGMT */
 	status = rockchip_pcie_read(rockchip, PCIE_CORE_CTRL);
 	status = 0x1 << ((status & PCIE_CORE_PL_CONF_LANE_MASK) >>
-- 
2.53.0