From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5D0A4C04FF8 for ; Tue, 16 Apr 2024 06:50:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=a+dWCICOm4bcMK1XfRLM3QTP4mfzUSY43Rm30yyalok=; b=DBJrfEclJ9hF5l pj3YWRHJYCuPf6Azc6y0FxJ6vy5wIH2NY75bnE+TnrGpWAq/UxjSikVrBu71S+0ujExptEFvzDUTA YYMwFEdb6khnUnR7n/UODOwhs+Gw2m87cB2Od15VwYW/4TggA5R2ZjMZuHU9gM7CgHsyEdbAk7L9n HiySfij4Tnf1Q1S4YaAS9yg+hoHEyt9wk07vpImuTOyroooi/Lb5lhdWF9OgLzPncQ2oLKkY8BMgQ P9j8qbs03ZHfSQQulIfGGS1HgHBobjW3IRkzqa6ECUjRdystx2RTg376WGE+VfttU8e6Udebf2DTZ M0hnntTna942KY248GvQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rwcdq-0000000B8ja-2cow; Tue, 16 Apr 2024 06:50:06 +0000 Received: from sin.source.kernel.org ([145.40.73.55]) by bombadil.infradead.org with esmtps (Exim 4.97.1 #2 (Red Hat Linux)) id 1rwcdn-0000000B8iF-0SeA; Tue, 16 Apr 2024 06:50:04 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 61ED4CE000E; Tue, 16 Apr 2024 06:50:00 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7DD27C113CE; Tue, 16 Apr 2024 06:49:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1713250199; bh=yfX5SuJiKsjZz5T4krQC0RPDEuHfvs/zvmFjAxx/zlY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LzS40nkMJsIBoNMyiBYU1dZiU1GtglSAeoOK9Wcywa3dOY58e3mqlh5jo9Uo3Wg2F bgDK0tl59DTrBOygg0MimxmV2SmnnMK3sWaXBhFO/CJhjGPCxtnk5Ia76in1UYvUBK vckfRAEjG0RHpNWyty6mmMfUa+d70IPhKPL2FQaHhubHznn8lySE+KogwTaJ59l1It NTQM+YyatNBircIy0BD3jOigDDKO2b0E8+exBqLDcMGDsa4gWo9HVGWxSrZL8T2Vfr 2sQ0oHzwEEpUKvd/TIIKAKi7z/0bxlEuMynqeleZ7TqaBos8awEksUEIqjQ87iO0QI DAkcQpckpO54w== Date: Tue, 16 Apr 2024 08:49:53 +0200 From: Niklas Cassel 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: References: <20240416-pci-rockchip-perst-fix-v1-1-4800b1d4d954@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20240416-pci-rockchip-perst-fix-v1-1-4800b1d4d954@linaro.org> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240415_235003_541808_0466FBD8 X-CRM114-Status: GOOD ( 23.88 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.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 > --- Reviewed-by: Niklas Cassel I sent a similar fix for the DWC-based rockchip driver a few weeks ago: https://lore.kernel.org/linux-pci/20240327152531.814392-1-cassel@kernel.org/ If your fix is picked up, it would be nice if mine got picked up as well, such that both drivers get fixed. Kind regards, Niklas _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel