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Mon, 15 Apr 2024 22:42:56 -0700 (PDT) From: Manivannan Sadhasivam Date: Tue, 16 Apr 2024 11:12:35 +0530 Subject: [PATCH] PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-Id: <20240416-pci-rockchip-perst-fix-v1-1-4800b1d4d954@linaro.org> X-B4-Tracking: v=1; b=H4sIAMoPHmYC/x2MQQqAMAzAviI9W3BFxvQr4kFq1SLo6EQE2d8dH hNIXkhiKgn66gWTW5OeRwFXV8DbdKyCOhcGaqhtWucxsqKdvPOmEaNYunDRB0PgjsiTm7sJShx Niv7Hw5jzB1Ks2+JoAAAA To: Shawn Lin , Lorenzo Pieralisi , =?utf-8?q?Krzysztof_Wilczy?= =?utf-8?q?=C5=84ski?= , Rob Herring , Bjorn Helgaas , Heiko Stuebner , Brian Norris Cc: linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mhi@lists.linux.dev, stable@vger.kernel.org, Slark Xiao , Manivannan Sadhasivam X-Mailer: b4 0.12.4 X-Developer-Signature: v=1; a=openpgp-sha256; l=3420; i=manivannan.sadhasivam@linaro.org; h=from:subject:message-id; bh=YzcwzdZL4XKreo1CF3wbVR5j3L/jHhRL6gcOR16pIWc=; b=owEBbQGS/pANAwAKAVWfEeb+kc71AcsmYgBmHg/crzU1Kkb1i9AqXVJ3hRXBiUx9TkrzmPVOq mUTZO2izYWJATMEAAEKAB0WIQRnpUMqgUjL2KRYJ5dVnxHm/pHO9QUCZh4P3AAKCRBVnxHm/pHO 9fTRCACK8wHhlIy/kLvZHbQzhc/EFgpLhGxBwGkKpiC9xOYMycx6mQuk8X1lpK2goCoKljGgktY e/Ti3YO9R2ntH5ycJCk/FK/xMY1wZffrkZYUg6QKtEvZoa/kWnzAIk+Vt9bagTtP++dRzu4C7bq 0Zgccetk3ERl1hzVhTluvHGB1AEHOCgCIyQTOS31v3gy2QmRLo4zDLQULZvtm6X0fNDJNQ2qlsW ftcyIPvXBVxIDlkQsY8t5m23kXP/PeVhPhIn/bvbB2rJ5g4Tsr15A3RwqVuSKt9C6V89PogwlGn qFNOcL9t95ugWM11fE3JxyLL309ww7DJvfLnqgnK8zPZDpqZ X-Developer-Key: i=manivannan.sadhasivam@linaro.org; a=openpgp; fpr=C668AEC3C3188E4C611465E7488550E901166008 Rockchip platforms use 'GPIO_ACTIVE_HIGH' flag in the devicetree definition for ep_gpio. This means, whatever the logical value set by the driver for the ep_gpio, physical line will output the same logic level. For instance, gpiod_set_value_cansleep(rockchip->ep_gpio, 0); --> Level low gpiod_set_value_cansleep(rockchip->ep_gpio, 1); --> Level high But while requesting the ep_gpio, GPIOD_OUT_HIGH flag is currently used. Now, this also causes the physical line to output 'high' creating trouble for endpoint devices during host reboot. When host reboot happens, the ep_gpio will initially output 'low' due to the GPIO getting reset to its POR value. Then during host controller probe, it will output 'high' due to GPIOD_OUT_HIGH flag. Then during rockchip_pcie_host_init_port(), it will first output 'low' and then 'high' indicating the completion of controller initialization. On the endpoint side, each output 'low' of ep_gpio is accounted for PERST# assert and 'high' for PERST# deassert. With the above mentioned flow during host reboot, endpoint will witness below state changes for PERST#: (1) PERST# assert - GPIO POR state (2) PERST# deassert - GPIOD_OUT_HIGH while requesting GPIO (3) PERST# assert - rockchip_pcie_host_init_port() (4) PERST# deassert - rockchip_pcie_host_init_port() Now the time interval between (2) and (3) is very short as both happen during the driver probe(), and this results in a race in the endpoint. Because, before completing the PERST# deassertion in (2), endpoint got another PERST# assert in (3). A proper way to fix this issue is to change the GPIOD_OUT_HIGH flag in (2) to GPIOD_OUT_LOW. Because the usual convention is to request the GPIO with a state corresponding to its 'initial/default' value and let the driver change the state of the GPIO when required. As per that, the ep_gpio should be requested with GPIOD_OUT_LOW as it corresponds to the POR value of '0' (PERST# assert in the endpoint). Then the driver can change the state of the ep_gpio later in rockchip_pcie_host_init_port() as per the initialization sequence. This fixes the firmware crash issue in Qcom based modems connected to Rockpro64 based board. Cc: # 4.9 Reported-by: Slark Xiao Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/ Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support") Signed-off-by: Manivannan Sadhasivam Reviewed-by: Niklas Cassel --- drivers/pci/controller/pcie-rockchip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- base-commit: 4cece764965020c22cff7665b18a012006359095 change-id: 20240416-pci-rockchip-perst-fix-88c922621d9a Best regards, diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c index 0ef2e622d36e..c07d7129f1c7 100644 --- a/drivers/pci/controller/pcie-rockchip.c +++ b/drivers/pci/controller/pcie-rockchip.c @@ -121,7 +121,7 @@ int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip) if (rockchip->is_rc) { rockchip->ep_gpio = devm_gpiod_get_optional(dev, "ep", - GPIOD_OUT_HIGH); + GPIOD_OUT_LOW); if (IS_ERR(rockchip->ep_gpio)) return dev_err_probe(dev, PTR_ERR(rockchip->ep_gpio), "failed to get ep GPIO\n");