From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0FD92155A57; Wed, 15 May 2024 21:18:48 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715807929; cv=none; b=WNk5N8UeVu90ZGOwUDAoXQpL97h6UINlSUr44mS3tlFN6BOUsup7mL+Z7a2Vrkz0li9jATQNdFZESMaa1PzlCZX0t/zUMNwPANmK0l5kS9ppn3aXEu8Dd5JaE7K9a7xKY86c+sZOamk0DnPIKrQ0gRRiFIE+u01taCXzkdhCrNY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715807929; c=relaxed/simple; bh=GV4ctJ7S6o2h1VMQ6K3QvFDmjV30mayxRlqtKeBqg1o=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=LGyevu7B8TA9LuKM5eFCIB1N1T9gVFROSFnNTUuP7IAJPMl7RJfsy3o6jGOqxm4ZfkksnwqyQaCxupQcPh5XUBLKkzqm8Wa85MBeVFJXuTMk8B5gmXwkUvW46J048nE2xGF7AZnTg0qq9PL1m6chVKhEaHk+3tZrvXpbwbE019A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=P3dFccox; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="P3dFccox" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 64A86C116B1; Wed, 15 May 2024 21:18:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715807928; bh=GV4ctJ7S6o2h1VMQ6K3QvFDmjV30mayxRlqtKeBqg1o=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=P3dFccoxomCIHJqy4XeaDnH+WifIbD1n9DRECJaYOjnB+pHNmRRXshO4DdAU+2FLb NlhEW6MafzcM0Jbcj+2VwkslZzf09wUlmRFmnFGeMCKCGuQiSiCXRyuvUskvBfYJ4L 9YDfoS7RbZBpcdhYecRCenElUV5ttxPpFcjhji8zret1J/jejjnGAfsCGAzIrywguU RNfW1bWqB9RHZNuQilAHblPZjMOR8GJcShYynFvRsCD97XsAt6bNHqTsLBltZ8qsUC nffGptSFneFjepbnxK3AjYyTduFnuCsBgq/8XBr0adLLkcxWlvo9sKO/GwSRTDbP98 2Q6fb1M5tmZeg== Date: Wed, 15 May 2024 16:18:46 -0500 From: Bjorn Helgaas To: Manivannan Sadhasivam Cc: Shawn Lin , Lorenzo Pieralisi , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , Rob Herring , Bjorn Helgaas , Heiko Stuebner , Brian Norris , 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 Subject: Re: [PATCH] PCI: rockchip: Use GPIOD_OUT_LOW flag while requesting ep_gpio Message-ID: <20240515211846.GA2139223@bhelgaas> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline 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: # 4.9 > Reported-by: Slark Xiao > Closes: https://lore.kernel.org/mhi/20240402045647.GG2933@thinkpad/ > Fixes: e77f847df54c ("PCI: rockchip: Add Rockchip PCIe controller support") > Signed-off-by: Manivannan Sadhasivam 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 >