From: Niklas Cassel <cassel@kernel.org>
To: "Lorenzo Pieralisi" <lpieralisi@kernel.org>,
"Krzysztof Wilczyński" <kw@linux.com>,
"Rob Herring" <robh@kernel.org>,
"Bjorn Helgaas" <bhelgaas@google.com>,
"Heiko Stuebner" <heiko@sntech.de>,
"Simon Xue" <xxm@rock-chips.com>,
"Kever Yang" <kever.yang@rock-chips.com>
Cc: Damien Le Moal <dlemoal@kernel.org>,
Niklas Cassel <cassel@kernel.org>,
Jianfeng Liu <liujianfeng1994@gmail.com>,
Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>,
stable@vger.kernel.org, linux-pci@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linux-rockchip@lists.infradead.org
Subject: [PATCH v3] PCI: dw-rockchip: Fix initial PERST# GPIO value
Date: Wed, 17 Apr 2024 18:42:26 +0200 [thread overview]
Message-ID: <20240417164227.398901-1-cassel@kernel.org> (raw)
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(-)
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);
--
2.44.0
next reply other threads:[~2024-04-17 16:42 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-17 16:42 Niklas Cassel [this message]
2024-04-30 8:38 ` [PATCH v3] PCI: dw-rockchip: Fix initial PERST# GPIO value Heiko Stübner
2024-05-15 21:20 ` Bjorn Helgaas
2024-05-17 11:22 ` Krzysztof Wilczyński
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