On Tue, Apr 16, 2024 at 11:12:35AM +0530, Manivannan Sadhasivam wrote: > 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: <stable@xxxxxxxxxxxxxxx> # 4.9 > Reported-by: Slark Xiao <slark_xiao@xxxxxxx> > Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/ > Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support") > Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> Applied by Krzysztof to pci/controller/rockchip, but his outgoing mail queue was broken. Trying to squeeze it into v6.10. > --- > drivers/pci/controller/pcie-rockchip.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > 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"); > > --- > base-commit: 4cece764965020c22cff7665b18a012006359095 > change-id: 20240416-pci-rockchip-perst-fix-88c922621d9a > > Best regards, > -- > Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx> >
