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=no 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 217DFC433E0 for ; Thu, 11 Jun 2020 12:45:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F378220747 for ; Thu, 11 Jun 2020 12:45:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726277AbgFKMpH (ORCPT ); Thu, 11 Jun 2020 08:45:07 -0400 Received: from mga18.intel.com ([134.134.136.126]:57880 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726254AbgFKMpH (ORCPT ); Thu, 11 Jun 2020 08:45:07 -0400 IronPort-SDR: 5OPaBHxRrV9kQecOgm8HIK90e/CAm4rOCMp8oBQmv79XAW3L0iaDWsD/gBQpkzap3Wu4ZSPvOF tfSySv09txbg== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jun 2020 05:45:05 -0700 IronPort-SDR: NPR+fUbBO5DWIwkJuW6tu4KPJ78c40SjkolJh2TiCjHVkey4ujGlqxqHIHHEYZWyTsA9lYIbN2 97nKqX62kkAw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.73,499,1583222400"; d="scan'208";a="275320085" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga006.jf.intel.com with ESMTP; 11 Jun 2020 05:45:04 -0700 Received: from andy by smile with local (Exim 4.93) (envelope-from ) id 1jjMZu-00CM50-Vp; Thu, 11 Jun 2020 15:45:06 +0300 Date: Thu, 11 Jun 2020 15:45:06 +0300 From: Andy Shevchenko To: Linus Walleij Cc: Hans de Goede , Mika Westerberg , "open list:GPIO SUBSYSTEM" , stable Subject: Re: [PATCH v2] pinctrl: baytrail: Fix pin being driven low for a while on gpiod_get(..., GPIOD_OUT_HIGH) Message-ID: <20200611124506.GW2428291@smile.fi.intel.com> References: <20200606093150.32882-1-hdegoede@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-gpio-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-gpio@vger.kernel.org On Wed, Jun 10, 2020 at 01:21:37PM +0200, Linus Walleij wrote: > On Sat, Jun 6, 2020 at 11:31 AM Hans de Goede wrote: > > > The pins on the Bay Trail SoC have separate input-buffer and output-buffer > > enable bits and a read of the level bit of the value register will always > > return the value from the input-buffer. > > > > The BIOS of a device may configure a pin in output-only mode, only enabling > > the output buffer, and write 1 to the level bit to drive the pin high. > > This 1 written to the level bit will be stored inside the data-latch of the > > output buffer. > > > > But a subsequent read of the value register will return 0 for the level bit > > because the input-buffer is disabled. This causes a read-modify-write as > > done by byt_gpio_set_direction() to write 0 to the level bit, driving the > > pin low! > > > > Before this commit byt_gpio_direction_output() relied on > > pinctrl_gpio_direction_output() to set the direction, followed by a call > > to byt_gpio_set() to apply the selected value. This causes the pin to > > go low between the pinctrl_gpio_direction_output() and byt_gpio_set() > > calls. > > > > Change byt_gpio_direction_output() to directly make the register > > modifications itself instead. Replacing the 2 subsequent writes to the > > value register with a single write. > > > > Note that the pinctrl code does not keep track internally of the direction, > > so not going through pinctrl_gpio_direction_output() is not an issue. > > > > This issue was noticed on a Trekstor SurfTab Twin 10.1. When the panel is > > already on at boot (no external monitor connected), then the i915 driver > > does a gpiod_get(..., GPIOD_OUT_HIGH) for the panel-enable GPIO. The > > temporarily going low of that GPIO was causing the panel to reset itself > > after which it would not show an image until it was turned off and back on > > again (until a full modeset was done on it). This commit fixes this. > > > > This commit also updates the byt_gpio_direction_input() to use direct > > register accesses instead of going through pinctrl_gpio_direction_input(), > > to keep it consistent with byt_gpio_direction_output(). > > > > Note for backporting, this commit depends on: > > commit e2b74419e5cc ("pinctrl: baytrail: Replace WARN with dev_info_once > > when setting direct-irq pin to output") > > > > Cc: stable@vger.kernel.org > > Fixes: 86e3ef812fe3 ("pinctrl: baytrail: Update gpio chip operations") > > Signed-off-by: Hans de Goede > > --- > > Note the factoring out of the direct IRQ mode warning is deliberately not > > split into a separate patch to make backporting this easier. > > Looks good to me, Thanks! > I expect this in a pull request from Andy for > fixes, alternatively I can apply it directly for fixes if Andy prefers > this. Mika or I will send a PR for v5.8-rcX at some point with fixes material. Though, there are GPIO stuff (PCA953x) which you can handle ;-) -- With Best Regards, Andy Shevchenko