6.6-stable review patch. If anyone has any objections, please let me know.
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From: Niklas Cassel cassel@kernel.org
commit 28b8d7793b8573563b3d45321376f36168d77b1e upstream.
PERST# is active low according to the PCIe specification.
However, the existing pcie-dw-rockchip.c driver does:
gpiod_set_value(..., 0); msleep(100); gpiod_set_value(..., 1);
when asserting + deasserting PERST#.
This is of course wrong, but because all the device trees for this compatible string have also incorrectly marked this GPIO as ACTIVE_HIGH:
$ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3568* $ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3588*
The actual toggling of PERST# is correct, and we cannot change it anyway, since that would break device tree compatibility.
However, this driver does request the GPIO to be initialized as GPIOD_OUT_HIGH, which does cause a silly sequence where PERST# gets toggled back and forth for no good reason.
Fix this by requesting the GPIO to be initialized as GPIOD_OUT_LOW (which for this driver means PERST# asserted).
This will avoid an unnecessary signal change where PERST# gets deasserted (by devm_gpiod_get_optional()) and then gets asserted (by rockchip_pcie_start_link()) just a few instructions later.
Before patch, debug prints on EP side, when booting RC:
[ 845.606810] pci: PERST# asserted by host! [ 852.483985] pci: PERST# de-asserted by host! [ 852.503041] pci: PERST# asserted by host! [ 852.610318] pci: PERST# de-asserted by host!
After patch, debug prints on EP side, when booting RC:
[ 125.107921] pci: PERST# asserted by host! [ 132.111429] pci: PERST# de-asserted by host!
This extra, very short, PERST# assertion + deassertion has been reported to cause issues with certain WLAN controllers, e.g. RTL8822CE.
Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller driver") Link: https://lore.kernel.org/linux-pci/20240417164227.398901-1-cassel@kernel.org Tested-by: Heiko Stuebner heiko@sntech.de Tested-by: Jianfeng Liu liujianfeng1994@gmail.com Signed-off-by: Niklas Cassel cassel@kernel.org Signed-off-by: Krzysztof Wilczyński kwilczynski@kernel.org Signed-off-by: Bjorn Helgaas bhelgaas@google.com Reviewed-by: Heiko Stuebner heiko@sntech.de Reviewed-by: Manivannan Sadhasivam manivannan.sadhasivam@linaro.org Cc: stable@vger.kernel.org # v5.15+ Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/pci/controller/dwc/pcie-dw-rockchip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c +++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c @@ -240,7 +240,7 @@ static int rockchip_pcie_resource_get(st return PTR_ERR(rockchip->apb_base);
rockchip->rst_gpio = devm_gpiod_get_optional(&pdev->dev, "reset", - GPIOD_OUT_HIGH); + GPIOD_OUT_LOW); if (IS_ERR(rockchip->rst_gpio)) return PTR_ERR(rockchip->rst_gpio);