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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6887DC48BD6 for ; Tue, 25 Jun 2019 05:27:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4C70420644 for ; Tue, 25 Jun 2019 05:27:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728021AbfFYF1u (ORCPT ); Tue, 25 Jun 2019 01:27:50 -0400 Received: from mx1.mailbox.org ([80.241.60.212]:13500 "EHLO mx1.mailbox.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726009AbfFYF1u (ORCPT ); Tue, 25 Jun 2019 01:27:50 -0400 Received: from smtp2.mailbox.org (smtp2.mailbox.org [80.241.60.241]) (using TLSv1.2 with cipher ECDHE-RSA-CHACHA20-POLY1305 (256/256 bits)) (No client certificate requested) by mx1.mailbox.org (Postfix) with ESMTPS id 75AFD5000F; Tue, 25 Jun 2019 07:27:47 +0200 (CEST) X-Virus-Scanned: amavisd-new at heinlein-support.de Received: from smtp2.mailbox.org ([80.241.60.241]) by spamfilter04.heinlein-hosting.de (spamfilter04.heinlein-hosting.de [80.241.56.122]) (amavisd-new, port 10030) with ESMTP id Hz6CaGAM_QKI; Tue, 25 Jun 2019 07:27:41 +0200 (CEST) Subject: Re: [PATCH 1/2 v9] serial: mctrl_gpio: Check if GPIO property exisits before requesting it To: Geert Uytterhoeven Cc: "open list:SERIAL DRIVERS" , Linux Kernel Mailing List , Mika Westerberg , Andy Shevchenko , Yegor Yefremov , Greg Kroah-Hartman , Giulio Benetti , Linus Walleij , Bartosz Golaszewski , "open list:GPIO SUBSYSTEM" References: <20190620062420.11650-1-sr@denx.de> <24bfb52c-6f77-b7cd-7421-9e6e4b0aa7d3@denx.de> From: Stefan Roese Message-ID: Date: Tue, 25 Jun 2019 07:27:33 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Geert, On 24.06.19 17:35, Geert Uytterhoeven wrote: > On Mon, Jun 24, 2019 at 5:29 PM Stefan Roese wrote: >> On 24.06.19 10:42, Geert Uytterhoeven wrote: >>> On Thu, Jun 20, 2019 at 8:24 AM Stefan Roese wrote: >>>> This patch adds a check for the GPIOs property existence, before the >>>> GPIO is requested. This fixes an issue seen when the 8250 mctrl_gpio >>>> support is added (2nd patch in this patch series) on x86 platforms using >>>> ACPI. >>>> >>>> Here Mika's comments from 2016-08-09: >>>> >>>> " >>>> I noticed that with v4.8-rc1 serial console of some of our Broxton >>>> systems does not work properly anymore. I'm able to see output but input >>>> does not work. >>>> >>>> I bisected it down to commit 4ef03d328769eddbfeca1f1c958fdb181a69c341 >>>> ("tty/serial/8250: use mctrl_gpio helpers"). >>>> >>>> The reason why it fails is that in ACPI we do not have names for GPIOs >>>> (except when _DSD is used) so we use the "idx" to index into _CRS GPIO >>>> resources. Now mctrl_gpio_init_noauto() goes through a list of GPIOs >>>> calling devm_gpiod_get_index_optional() passing "idx" of 0 for each. The >>>> UART device in Broxton has following (simplified) ACPI description: >>>> >>>> Device (URT4) >>>> { >>>> ... >>>> Name (_CRS, ResourceTemplate () { >>>> GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly, >>>> "\\_SB.GPO0", 0x00, ResourceConsumer) >>>> { >>>> 0x003A >>>> } >>>> GpioIo (Exclusive, PullDefault, 0x0000, 0x0000, IoRestrictionOutputOnly, >>>> "\\_SB.GPO0", 0x00, ResourceConsumer) >>>> { >>>> 0x003D >>>> } >>>> }) >>>> >>>> In this case it finds the first GPIO (0x003A which happens to be RX pin >>>> for that UART), turns it into GPIO which then breaks input for the UART >>>> device. This also breaks systems with bluetooth connected to UART (those >>>> typically have some GPIOs in their _CRS). >>>> >>>> Any ideas how to fix this? >>>> >>>> We cannot just drop the _CRS index lookup fallback because that would >>>> break many existing machines out there so maybe we can limit this to >>>> only DT enabled machines. Or alternatively probe if the property first >>>> exists before trying to acquire the GPIOs (using >>>> device_property_present()). >>>> " >>>> >>>> This patch implements the fix suggested by Mika in his statement above. >>>> >>>> Signed-off-by: Stefan Roese > >>>> --- a/drivers/tty/serial/serial_mctrl_gpio.c >>>> +++ b/drivers/tty/serial/serial_mctrl_gpio.c > >>>> @@ -116,6 +117,19 @@ struct mctrl_gpios *mctrl_gpio_init_noauto(struct device *dev, unsigned int idx) >>>> >>>> for (i = 0; i < UART_GPIO_MAX; i++) { >>>> enum gpiod_flags flags; >>>> + char *gpio_str; >>>> + bool present; >>>> + >>>> + /* Check if GPIO property exists and continue if not */ >>>> + gpio_str = kasprintf(GFP_KERNEL, "%s-gpios", >>>> + mctrl_gpios_desc[i].name); >>> >>> This will silently break DTBs using "(cts|dsr|dcd|rng|rts|dtr)-gpio" instead >>> of "(cts|dsr|dcd|rng|rts|dtr)-gpios". >> >> Should both options be supported ("cts-gpio" vs "cts-gpios")? >> Documentation/devicetree/bindings/serial/serial.txt only mentions >> the "-gpios" variant. > > Well, the "-gpio" variant is deprecated, but still supported by > devm_gpiod_get_index_optional(), and there are active users in upstream > DTS files. > > My main objection is (trying to) replicate the matching logic inside > gpiolib.c, causing subtle semantic differences. And keeping it consistent, > of course. > > It would be nice if this could be fixed inside acpi_find_gpio(), so > users don't need to be updated. There may be other subsystems where > the difference between DT and ACPI may cause issues, unbeknownst. Sure, I can fix this. I would prefer to do this in a follow-up patch though, if nobody objects. Thanks, Stefan