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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>
77 lines
3.0 KiB
Diff
77 lines
3.0 KiB
Diff
From 28b8d7793b8573563b3d45321376f36168d77b1e Mon Sep 17 00:00:00 2001
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From: Niklas Cassel <cassel@kernel.org>
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Date: Wed, 17 Apr 2024 18:42:26 +0200
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Subject: [PATCH] PCI: dw-rockchip: Fix initial PERST# GPIO value
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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PERST# is active low according to the PCIe specification.
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However, the existing pcie-dw-rockchip.c driver does:
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gpiod_set_value(..., 0); msleep(100); gpiod_set_value(..., 1);
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when asserting + deasserting PERST#.
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This is of course wrong, but because all the device trees for this
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compatible string have also incorrectly marked this GPIO as ACTIVE_HIGH:
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$ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3568*
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$ git grep -B 10 reset-gpios arch/arm64/boot/dts/rockchip/rk3588*
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The actual toggling of PERST# is correct, and we cannot change it anyway,
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since that would break device tree compatibility.
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However, this driver does request the GPIO to be initialized as
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GPIOD_OUT_HIGH, which does cause a silly sequence where PERST# gets
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toggled back and forth for no good reason.
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Fix this by requesting the GPIO to be initialized as GPIOD_OUT_LOW (which
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for this driver means PERST# asserted).
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This will avoid an unnecessary signal change where PERST# gets deasserted
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(by devm_gpiod_get_optional()) and then gets asserted (by
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rockchip_pcie_start_link()) just a few instructions later.
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Before patch, debug prints on EP side, when booting RC:
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[ 845.606810] pci: PERST# asserted by host!
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[ 852.483985] pci: PERST# de-asserted by host!
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[ 852.503041] pci: PERST# asserted by host!
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[ 852.610318] pci: PERST# de-asserted by host!
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After patch, debug prints on EP side, when booting RC:
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[ 125.107921] pci: PERST# asserted by host!
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[ 132.111429] pci: PERST# de-asserted by host!
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This extra, very short, PERST# assertion + deassertion has been reported to
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cause issues with certain WLAN controllers, e.g. RTL8822CE.
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Fixes: 0e898eb8df4e ("PCI: rockchip-dwc: Add Rockchip RK356X host controller driver")
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Link: https://lore.kernel.org/linux-pci/20240417164227.398901-1-cassel@kernel.org
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Tested-by: Heiko Stuebner <heiko@sntech.de>
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Tested-by: Jianfeng Liu <liujianfeng1994@gmail.com>
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Signed-off-by: Niklas Cassel <cassel@kernel.org>
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Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
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Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
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Reviewed-by: Heiko Stuebner <heiko@sntech.de>
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Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
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Cc: stable@vger.kernel.org # v5.15+
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---
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drivers/pci/controller/dwc/pcie-dw-rockchip.c | 2 +-
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1 file changed, 1 insertion(+), 1 deletion(-)
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--- a/drivers/pci/controller/dwc/pcie-dw-rockchip.c
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+++ b/drivers/pci/controller/dwc/pcie-dw-rockchip.c
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@@ -240,7 +240,7 @@ static int rockchip_pcie_resource_get(st
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return PTR_ERR(rockchip->apb_base);
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rockchip->rst_gpio = devm_gpiod_get_optional(&pdev->dev, "reset",
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- GPIOD_OUT_HIGH);
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+ GPIOD_OUT_LOW);
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if (IS_ERR(rockchip->rst_gpio))
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return PTR_ERR(rockchip->rst_gpio);
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