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rockchip: dw-rockchip: Fix initial PERST# GPIO value

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Import patch from mainline Linux to fix issue with PERST# signal
polarity.

Quote from commit message:
"This extra, very short, PERST# assertion + deassertion has been
reported to cause issues with certain WLAN controllers, e.g. RTL8822CE."

Signed-off-by: Daniel Golle <daniel@makrotopia.org>
This commit is contained in:
Daniel Golle 2024-07-30 00:37:21 +01:00
parent a158e7ed43
commit 940f83cc8d
1 changed files with 76 additions and 0 deletions
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76
target/linux/rockchip/patches-6.6/310-PCI-dw-rockchip-Fix-initial-PERST-GPIO-value.patch Normal file
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@ -0,0 +1,76 @@
From 28b8d7793b8573563b3d45321376f36168d77b1e Mon Sep 17 00:00:00 2001
From: Niklas Cassel <cassel@kernel.org>
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 <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+
---
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);