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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,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 BA8E8C433E0 for ; Thu, 9 Jul 2020 13:36:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9BAE4206DF for ; Thu, 9 Jul 2020 13:36:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726575AbgGINgN (ORCPT ); Thu, 9 Jul 2020 09:36:13 -0400 Received: from mga11.intel.com ([192.55.52.93]:65395 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726480AbgGINgM (ORCPT ); Thu, 9 Jul 2020 09:36:12 -0400 IronPort-SDR: gxP3V5AVSYi82NCwg0FtJ59wvAEKoQP6sZjs3kiwT4MVgR1Kdecp2CGss6ALqhwUJh61bWuUtg uk/tpskFnjCg== X-IronPort-AV: E=McAfee;i="6000,8403,9676"; a="146078911" X-IronPort-AV: E=Sophos;i="5.75,331,1589266800"; d="scan'208";a="146078911" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 09 Jul 2020 06:36:12 -0700 IronPort-SDR: UboHJqh1nndBjOld5+xN9RqqWuNwLZizV1X/1HZBDQgavEA+WWzfEFH2R70Yko5iGln5KPA3ON A3TGACA3fk/Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.75,331,1589266800"; d="scan'208";a="358442727" Received: from smile.fi.intel.com (HELO smile) ([10.237.68.40]) by orsmga001.jf.intel.com with ESMTP; 09 Jul 2020 06:36:08 -0700 Received: from andy by smile with local (Exim 4.94) (envelope-from ) id 1jtWif-000rnE-BI; Thu, 09 Jul 2020 16:36:09 +0300 Date: Thu, 9 Jul 2020 16:36:09 +0300 From: Andy Shevchenko To: Hans de Goede Cc: Thierry Reding , Uwe =?iso-8859-1?Q?Kleine-K=F6nig?= , Jani Nikula , Joonas Lahtinen , Rodrigo Vivi , Ville =?iso-8859-1?Q?Syrj=E4l=E4?= , "Rafael J . Wysocki" , Len Brown , linux-pwm@vger.kernel.org, intel-gfx , dri-devel@lists.freedesktop.org, Mika Westerberg , linux-acpi@vger.kernel.org Subject: Re: [PATCH v4 05/16] pwm: lpss: Use pwm_lpss_apply() when restoring state on resume Message-ID: <20200709133609.GY3703480@smile.fi.intel.com> References: <20200708211432.28612-1-hdegoede@redhat.com> <20200708211432.28612-6-hdegoede@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200708211432.28612-6-hdegoede@redhat.com> Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Wed, Jul 08, 2020 at 11:14:21PM +0200, Hans de Goede wrote: > Before this commit a suspend + resume of the LPSS PWM controller > would result in the controller being reset to its defaults of > output-freq = clock/256, duty-cycle=100%, until someone changes > to the output-freq and/or duty-cycle are made. > > This problem has been masked so far because the main consumer > (the i915 driver) was always making duty-cycle changes on resume. > With the conversion of the i915 driver to the atomic PWM API the > driver now only disables/enables the PWM on suspend/resume leaving > the output-freq and duty as is, triggering this problem. > > The LPSS PWM controller has a mechanism where the ctrl register value > and the actual base-unit and on-time-div values used are latched. When > software sets the SW_UPDATE bit then at the end of the current PWM cycle, > the new values from the ctrl-register will be latched into the actual > registers, and the SW_UPDATE bit will be cleared. > > The problem is that before this commit our suspend/resume handling > consisted of simply saving the PWM ctrl register on suspend and > restoring it on resume, without setting the PWM_SW_UPDATE bit. > When the controller has lost its state over a suspend/resume and thus > has been reset to the defaults, just restoring the register is not > enough. We must also set the SW_UPDATE bit to tell the controller to > latch the restored values into the actual registers. > > Fixing this problem is not as simple as just or-ing in the value which > is being restored with SW_UPDATE. If the PWM was enabled before we must > write the new settings + PWM_SW_UPDATE before setting PWM_ENABLE. > We must also wait for PWM_SW_UPDATE to become 0 again and depending on the > model we must do this either before or after the setting of PWM_ENABLE. > > All the necessary logic for doing this is already present inside > pwm_lpss_apply(), so instead of duplicating this inside the resume > handler, this commit makes the resume handler use pwm_lpss_apply() to > restore the settings when necessary. This fixes the output-freq and > duty-cycle being reset to their defaults on resume. ... > +static int __pwm_lpss_apply(struct pwm_chip *chip, struct pwm_device *pwm, > + const struct pwm_state *state, bool from_resume) > { > struct pwm_lpss_chip *lpwm = to_lpwm(chip); > int ret; > > if (state->enabled) { > if (!pwm_is_enabled(pwm)) { > - pm_runtime_get_sync(chip->dev); > + if (!from_resume) > + pm_runtime_get_sync(chip->dev); > + > ret = pwm_lpss_is_updating(pwm); > if (ret) { > - pm_runtime_put(chip->dev); > + if (!from_resume) > + pm_runtime_put(chip->dev); > + > return ret; > } > pwm_lpss_prepare(lpwm, pwm, state->duty_cycle, state->period); > pwm_lpss_cond_enable(pwm, lpwm->info->bypass == false); > ret = pwm_lpss_wait_for_update(pwm); > if (ret) { > - pm_runtime_put(chip->dev); > + if (!from_resume) > + pm_runtime_put(chip->dev); > + > return ret; > } > pwm_lpss_cond_enable(pwm, lpwm->info->bypass == true); > } > } else if (pwm_is_enabled(pwm)) { > pwm_lpss_write(pwm, pwm_lpss_read(pwm) & ~PWM_ENABLE); > - pm_runtime_put(chip->dev); > + > + if (!from_resume) > + pm_runtime_put(chip->dev); > } I'm wondering if splitting more will make this look better, like: ... if (from_resume) { ret = pwm_lpss_prepare_enable(...); // whatever name you think suits better } else { pm_runtime_get_sync(...); ret = pwm_lpss_prepare_enable(...); if (ret) pm_runtime_put(...); } ... -- With Best Regards, Andy Shevchenko