From patchwork Fri Jan 20 12:00:18 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= X-Patchwork-Id: 13109671 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 33B04C25B4E for ; Fri, 20 Jan 2023 12:00:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230036AbjATMAj (ORCPT ); Fri, 20 Jan 2023 07:00:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39752 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230040AbjATMAi (ORCPT ); Fri, 20 Jan 2023 07:00:38 -0500 Received: from metis.ext.pengutronix.de (metis.ext.pengutronix.de [IPv6:2001:67c:670:201:290:27ff:fe1d:cc33]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3C1C1A25B4 for ; Fri, 20 Jan 2023 04:00:35 -0800 (PST) Received: from drehscheibe.grey.stw.pengutronix.de ([2a0a:edc0:0:c01:1d::a2]) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1pIq4F-0001AP-D5; Fri, 20 Jan 2023 13:00:23 +0100 Received: from [2a0a:edc0:0:900:1d::77] (helo=ptz.office.stw.pengutronix.de) by drehscheibe.grey.stw.pengutronix.de with esmtp (Exim 4.94.2) (envelope-from ) id 1pIq4E-007MQ3-8T; Fri, 20 Jan 2023 13:00:22 +0100 Received: from ukl by ptz.office.stw.pengutronix.de with local (Exim 4.94.2) (envelope-from ) id 1pIq4D-00ENg0-Hm; Fri, 20 Jan 2023 13:00:21 +0100 From: =?utf-8?q?Uwe_Kleine-K=C3=B6nig?= To: Lee Jones , Daniel Thompson , Jingoo Han , Liam Girdwood , Mark Brown Cc: Thierry Reding , Helge Deller , linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, kernel@pengutronix.de Subject: [PATCH v2 2/2] backlight: pwm_bl: Don't rely on a disabled PWM emiting inactive state Date: Fri, 20 Jan 2023 13:00:18 +0100 Message-Id: <20230120120018.161103-3-u.kleine-koenig@pengutronix.de> X-Mailer: git-send-email 2.39.0 In-Reply-To: <20230120120018.161103-1-u.kleine-koenig@pengutronix.de> References: <20230120120018.161103-1-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=3378; i=u.kleine-koenig@pengutronix.de; h=from:subject; bh=3M18JepJfTGb5m9P8ayAdk02ozkDerKKEZZRJa5QyAI=; b=owEBbQGS/pANAwAKAcH8FHityuwJAcsmYgBjyoJJt15jx6Kow8IBg/U6EFtJQCoxDIfgvjhFmyDp lLphq6mJATMEAAEKAB0WIQR+cioWkBis/z50pAvB/BR4rcrsCQUCY8qCSQAKCRDB/BR4rcrsCba/B/ 9BccL7O6OygZX40tqrIMZFJcxCFqDYsp1WQ2xg+Ag+GGW4eHBSOJI51XnGPp/Bje3wH4ZtAf7RCffS gQdyPbNWla2Vo3m5Zqk0qC0g7pknzOraRxrd4suD1s4s1xBIwoOnmJGVV3egHYiLSXd957QGs7BkTH 7mrpV61OUHQwEcJb+QYEZcrXkBtuG5T+6zK04qKR48kgENjz9JElhUMLJaI3zRdcqrYtXRZmnJmiMe X8FnYT1YlMycu0WHQ37Nmj5FP8PgmaGwZzUBrNLrJKEfr+plvrxwpkcBrAqIjdsOcCJL5GbKAt7DJ9 j11B6BSD1qrcLKa0d2kHxgvuOBfHQU X-Developer-Key: i=u.kleine-koenig@pengutronix.de; a=openpgp; fpr=0D2511F322BFAB1C1580266BE2DCDD9132669BD6 X-SA-Exim-Connect-IP: 2a0a:edc0:0:c01:1d::a2 X-SA-Exim-Mail-From: ukl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-fbdev@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fbdev@vger.kernel.org Most but not all PWMs drive the PWM pin to its inactive state when disabled. However if there is no enable_gpio and no regulator the PWM must drive the inactive state to actually disable the backlight. So keep the PWM on in this case. Note that to determine if there is a regulator some effort is required because it might happen that there isn't actually one but the regulator core gave us a dummy. (A nice side effect is that this makes the regulator actually optional even on fully constrained systems.) This fixes backlight disabling e.g. on i.MX6 when an inverted PWM is used. Hint for the future: If this change results in a regression, the bug is in the lowlevel PWM driver. Signed-off-by: Uwe Kleine-König Reviewed-by: Daniel Thompson --- drivers/video/backlight/pwm_bl.c | 30 ++++++++++++++++++++++-------- 1 file changed, 22 insertions(+), 8 deletions(-) diff --git a/drivers/video/backlight/pwm_bl.c b/drivers/video/backlight/pwm_bl.c index 0509fecd5715..fb388148d98f 100644 --- a/drivers/video/backlight/pwm_bl.c +++ b/drivers/video/backlight/pwm_bl.c @@ -45,9 +45,11 @@ static void pwm_backlight_power_on(struct pwm_bl_data *pb) if (pb->enabled) return; - err = regulator_enable(pb->power_supply); - if (err < 0) - dev_err(pb->dev, "failed to enable power supply\n"); + if (pb->power_supply) { + err = regulator_enable(pb->power_supply); + if (err < 0) + dev_err(pb->dev, "failed to enable power supply\n"); + } if (pb->post_pwm_on_delay) msleep(pb->post_pwm_on_delay); @@ -69,7 +71,8 @@ static void pwm_backlight_power_off(struct pwm_bl_data *pb) if (pb->pwm_off_delay) msleep(pb->pwm_off_delay); - regulator_disable(pb->power_supply); + if (pb->power_supply) + regulator_disable(pb->power_supply); pb->enabled = false; } @@ -109,8 +112,16 @@ static int pwm_backlight_update_status(struct backlight_device *bl) pwm_backlight_power_off(pb); pwm_get_state(pb->pwm, &state); - state.enabled = false; state.duty_cycle = 0; + /* + * We cannot assume a disabled PWM to drive its output to the + * inactive state. If we have an enable GPIO and/or a regulator + * we assume that this isn't relevant and we can disable the PWM + * to save power. If however there is neither an enable GPIO nor + * a regulator keep the PWM on be sure to get a constant + * inactive output. + */ + state.enabled = !pb->power_supply && !pb->enable_gpio; pwm_apply_state(pb->pwm, &state); } @@ -408,7 +419,7 @@ static int pwm_backlight_initial_power_state(const struct pwm_bl_data *pb) if (pb->enable_gpio && gpiod_get_value_cansleep(pb->enable_gpio) == 0) active = false; - if (!regulator_is_enabled(pb->power_supply)) + if (pb->power_supply && !regulator_is_enabled(pb->power_supply)) active = false; if (!pwm_is_enabled(pb->pwm)) @@ -489,10 +500,13 @@ static int pwm_backlight_probe(struct platform_device *pdev) goto err_alloc; } - pb->power_supply = devm_regulator_get(&pdev->dev, "power"); + pb->power_supply = devm_regulator_get_optional(&pdev->dev, "power"); if (IS_ERR(pb->power_supply)) { ret = PTR_ERR(pb->power_supply); - goto err_alloc; + if (ret == -ENODEV) + pb->power_supply = NULL; + else + goto err_alloc; } pb->pwm = devm_pwm_get(&pdev->dev, NULL);