From: Niklas Cassel <cassel@xxxxxxxxxx>
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@xxxxxxxxxx
Tested-by: Heiko Stuebner <heiko@xxxxxxxxx>
Tested-by: Jianfeng Liu <liujianfeng1994@xxxxxxxxx>
Signed-off-by: Niklas Cassel <cassel@xxxxxxxxxx>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@xxxxxxxxxx>
Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Reviewed-by: Heiko Stuebner <heiko@xxxxxxxxx>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx # v5.15+
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from cassel@xxxxxxxxxx are
queue-6.10/pci-tegra194-set-ep-alignment-restriction-for-inboun.patch
queue-6.10/pci-dw-rockchip-fix-initial-perst-gpio-value.patch
queue-6.10/pci-keystone-don-t-enable-bar-0-for-am654x.patch
queue-6.10/ata-libata-scsi-do-not-overwrite-valid-sense-data-when-ck_cond-1.patch
queue-6.10/dm-call-dm_revalidate_zones-after-setting-the-queue-.patch
queue-6.10/pci-endpoint-pci-epf-test-make-use-of-cached-epc_fea.patch
queue-6.10/pci-qcom-ep-disable-resources-unconditionally-during.patch
queue-6.10/ata-libata-scsi-fix-offsets-for-the-fixed-format-sense-data.patch
queue-6.10/pci-rockchip-use-gpiod_out_low-flag-while-requesting-ep_gpio.patch
queue-6.10/ata-libata-scsi-honor-the-d_sense-bit-for-ck_cond-1-and-no-error.patch
