linux-kernel - [PATCH 2/3] PCI: rockchip-host: comment danger of 5.0 GT/s speed

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Message-ID: <b04ed0deb42c914847dd28233010f9573d6b5902.1763197368.git.geraldogabriel@gmail.com>
Date: Sat, 15 Nov 2025 06:10:36 -0300
From: Geraldo Nascimento <geraldogabriel@...il.com>
To: linux-rockchip@...ts.infradead.org
Cc: Shawn Lin <shawn.lin@...k-chips.com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	Krzysztof Wilczyński <kwilczynski@...nel.org>,
	Manivannan Sadhasivam <mani@...nel.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,
	devicetree@...r.kernel.org,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Johan Jonker <jbx6244@...il.com>,
	Geraldo Nascimento <geraldogabriel@...il.com>,
	Dragan Simic <dsimic@...jaro.org>
Subject: [PATCH 2/3] PCI: rockchip-host: comment danger of 5.0 GT/s speed

According to Rockchip sources, there is grave danger in enabling 5.0
GT/s speed for this core. Add a comment documenting that danger and
discouraging end-users from forcing higher speed through DT changes.

Link: https://lore.kernel.org/all/ffd05070-9879-4468-94e3-b88968b4c21b@rock-chips.com/
Reported-by: Shawn Lin <shawn.lin@...k-chips.com>
Signed-off-by: Geraldo Nascimento <geraldogabriel@...il.com>
---
 drivers/pci/controller/pcie-rockchip-host.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/pci/controller/pcie-rockchip-host.c b/drivers/pci/controller/pcie-rockchip-host.c
index ee1822ca01db..7e6ff76466b7 100644
--- a/drivers/pci/controller/pcie-rockchip-host.c
+++ b/drivers/pci/controller/pcie-rockchip-host.c
@@ -332,6 +332,11 @@ static int rockchip_pcie_host_init_port(struct rockchip_pcie *rockchip)
 		/*
 		 * Enable retrain for gen2. This should be configured only after
 		 * gen1 finished.
+		 *
+		 * According to Rockchip this path is dangerous and may lead to
+		 * catastrophic failure. Even if the odds are small, users are
+		 * still discouraged to engage the corresponding DT option.
+		 *
 		 */
 		status = rockchip_pcie_read(rockchip, PCIE_RC_CONFIG_CR + PCI_EXP_LNKCTL2);
 		status &= ~PCI_EXP_LNKCTL2_TLS;
-- 
2.49.0