| Message ID | 20240417164227.398901-1-cassel@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] PCI: dw-rockchip: Fix initial PERST# GPIO value | expand |
Am Mittwoch, 17. April 2024, 18:42:26 CEST schrieb Niklas Cassel: > 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") > Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com> > Tested-by: Heiko Stuebner <heiko@sntech.de> > Signed-off-by: Niklas Cassel <cassel@kernel.org> > Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> > Cc: stable@vger.kernel.org # 5.15+ Reviewed-by: Heiko Stuebner <heiko@sntech.de> it also matches what the vendor kernel does.
diff --git a/drivers/pci/controller/dwc/pcie-dw-rockchip.c b/drivers/pci/controller/dwc/pcie-dw-rockchip.c index d6842141d384..a909e42b4273 100644 --- 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(struct platform_device *pdev, 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);
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") Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com> Tested-by: Heiko Stuebner <heiko@sntech.de> Signed-off-by: Niklas Cassel <cassel@kernel.org> Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org> Cc: stable@vger.kernel.org # 5.15+ --- Changes since v2: -Picked up tag from Heiko. -Change subject (Bjorn). -s/PERST/PERST#/ (Bjorn). drivers/pci/controller/dwc/pcie-dw-rockchip.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)