From: Bjorn Helgaas <helgaas@kernel.org>
To: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc: "Shawn Lin" <shawn.lin@rock-chips.com>,
"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>,
"Brian Norris" <briannorris@chromium.org>,
linux-pci@vger.kernel.org, linux-rockchip@lists.infradead.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org, mhi@lists.linux.dev,
stable@vger.kernel.org, "Slark Xiao" <slark_xiao@163.com>
Subject: Re: [PATCH] PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio
Date: Wed, 15 May 2024 16:18:46 -0500 [thread overview]
Message-ID: <20240515211846.GA2139223@bhelgaas> (raw)
In-Reply-To: <20240416-pci-rockchip-perst-fix-v1-1-4800b1d4d954@linaro.org>
On Tue, Apr 16, 2024 at 11:12:35AM +0530, Manivannan Sadhasivam wrote:
> Rockchip platforms use 'GPIO_ACTIVE_HIGH' flag in the devicetree definition
> for ep_gpio. This means, whatever the logical value set by the driver for
> the ep_gpio, physical line will output the same logic level.
>
> For instance,
>
> gpiod_set_value_cansleep(rockchip->ep_gpio, 0); --> Level low
> gpiod_set_value_cansleep(rockchip->ep_gpio, 1); --> Level high
>
> But while requesting the ep_gpio, GPIOD_OUT_HIGH flag is currently used.
> Now, this also causes the physical line to output 'high' creating trouble
> for endpoint devices during host reboot.
>
> When host reboot happens, the ep_gpio will initially output 'low' due to
> the GPIO getting reset to its POR value. Then during host controller probe,
> it will output 'high' due to GPIOD_OUT_HIGH flag. Then during
> rockchip_pcie_host_init_port(), it will first output 'low' and then 'high'
> indicating the completion of controller initialization.
>
> On the endpoint side, each output 'low' of ep_gpio is accounted for PERST#
> assert and 'high' for PERST# deassert. With the above mentioned flow during
> host reboot, endpoint will witness below state changes for PERST#:
>
> (1) PERST# assert - GPIO POR state
> (2) PERST# deassert - GPIOD_OUT_HIGH while requesting GPIO
> (3) PERST# assert - rockchip_pcie_host_init_port()
> (4) PERST# deassert - rockchip_pcie_host_init_port()
>
> Now the time interval between (2) and (3) is very short as both happen
> during the driver probe(), and this results in a race in the endpoint.
> Because, before completing the PERST# deassertion in (2), endpoint got
> another PERST# assert in (3).
>
> A proper way to fix this issue is to change the GPIOD_OUT_HIGH flag in (2)
> to GPIOD_OUT_LOW. Because the usual convention is to request the GPIO with
> a state corresponding to its 'initial/default' value and let the driver
> change the state of the GPIO when required.
>
> As per that, the ep_gpio should be requested with GPIOD_OUT_LOW as it
> corresponds to the POR value of '0' (PERST# assert in the endpoint). Then
> the driver can change the state of the ep_gpio later in
> rockchip_pcie_host_init_port() as per the initialization sequence.
>
> This fixes the firmware crash issue in Qcom based modems connected to
> Rockpro64 based board.
>
> Cc: <stable@vger.kernel.org> # 4.9
> Reported-by: Slark Xiao <slark_xiao@163.com>
> Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/
> Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support")
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Applied by Krzysztof to pci/controller/rockchip, but his outgoing mail
queue was broken. Trying to squeeze it into v6.10.
> ---
> drivers/pci/controller/pcie-rockchip.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/controller/pcie-rockchip.c b/drivers/pci/controller/pcie-rockchip.c
> index 0ef2e622d36e..c07d7129f1c7 100644
> --- a/drivers/pci/controller/pcie-rockchip.c
> +++ b/drivers/pci/controller/pcie-rockchip.c
> @@ -121,7 +121,7 @@ int rockchip_pcie_parse_dt(struct rockchip_pcie *rockchip)
>
> if (rockchip->is_rc) {
> rockchip->ep_gpio = devm_gpiod_get_optional(dev, "ep",
> - GPIOD_OUT_HIGH);
> + GPIOD_OUT_LOW);
> if (IS_ERR(rockchip->ep_gpio))
> return dev_err_probe(dev, PTR_ERR(rockchip->ep_gpio),
> "failed to get ep GPIO\n");
>
> ---
> base-commit: 4cece764965020c22cff7665b18a012006359095
> change-id: 20240416-pci-rockchip-perst-fix-88c922621d9a
>
> Best regards,
> --
> Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
>
next prev parent reply other threads:[~2024-05-15 21:18 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-16 5:42 [PATCH] PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio Manivannan Sadhasivam
2024-04-16 6:49 ` Niklas Cassel
2024-04-16 9:15 ` Manivannan Sadhasivam
2024-05-15 21:18 ` Bjorn Helgaas [this message]
2024-05-17 11:21 ` Krzysztof Wilczyński
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