From 28b8d7793b8573563b3d45321376f36168d77b1e Mon Sep 17 00:00:00 2001 From: Niklas Cassel Date: Wed, 17 Apr 2024 18:42:26 +0200 Subject: [PATCH] PCI: dw-rockchip: Fix initial PERST# GPIO value MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Tested-by: Jianfeng Liu Signed-off-by: Niklas Cassel Signed-off-by: Krzysztof Wilczyński Signed-off-by: Bjorn Helgaas Reviewed-by: Heiko Stuebner Reviewed-by: Manivannan Sadhasivam Cc: stable@vger.kernel.org # v5.15+ --- 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);