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28b8d7793b
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:
|
||
|---|---|---|
| .. | ||
| Kconfig | ||
| Makefile | ||
| pci-dra7xx.c | ||
| pci-exynos.c | ||
| pci-imx6.c | ||
| pci-keystone.c | ||
| pci-layerscape-ep.c | ||
| pci-layerscape.c | ||
| pci-meson.c | ||
| pcie-al.c | ||
| pcie-armada8k.c | ||
| pcie-artpec6.c | ||
| pcie-bt1.c | ||
| pcie-designware-ep.c | ||
| pcie-designware-host.c | ||
| pcie-designware-plat.c | ||
| pcie-designware.c | ||
| pcie-designware.h | ||
| pcie-dw-rockchip.c | ||
| pcie-fu740.c | ||
| pcie-hisi.c | ||
| pcie-histb.c | ||
| pcie-intel-gw.c | ||
| pcie-keembay.c | ||
| pcie-kirin.c | ||
| pcie-qcom-ep.c | ||
| pcie-qcom.c | ||
| pcie-rcar-gen4.c | ||
| pcie-spear13xx.c | ||
| pcie-tegra194-acpi.c | ||
| pcie-tegra194.c | ||
| pcie-uniphier-ep.c | ||
| pcie-uniphier.c | ||
| pcie-visconti.c | ||