5.15-stable review patch. If anyone has any objections, please let me know.
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From: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org
commit 840b7a5edf88fe678c60dee88a135647c0ea4375 upstream.
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.
Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support") Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/ Link: https://lore.kernel.org/linux-pci/20240416-pci-rockchip-perst-fix-v1-1-4800b... Reported-by: Slark Xiao slark_xiao@163.com Signed-off-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Signed-off-by: Krzysztof Wilczyński kwilczynski@kernel.org Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Niklas Cassel cassel@kernel.org Cc: stable@vger.kernel.org # v4.9 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/controller/pcie-rockchip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pci/controller/pcie-rockchip.c +++ b/drivers/pci/controller/pcie-rockchip.c @@ -120,7 +120,7 @@ int rockchip_pcie_parse_dt(struct rockch
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");