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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 56B32EB64D9 for ; Tue, 4 Jul 2023 15:31:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231689AbjGDPb5 convert rfc822-to-8bit (ORCPT ); Tue, 4 Jul 2023 11:31:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231610AbjGDPbz (ORCPT ); Tue, 4 Jul 2023 11:31:55 -0400 Received: from unicorn.mansr.com (unicorn.mansr.com [81.2.72.234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1B3581B2; Tue, 4 Jul 2023 08:31:54 -0700 (PDT) Received: from raven.mansr.com (raven.mansr.com [81.2.72.235]) by unicorn.mansr.com (Postfix) with ESMTPS id 0FA9115360; Tue, 4 Jul 2023 16:31:52 +0100 (BST) Received: by raven.mansr.com (Postfix, from userid 51770) id B9EEA219FC1; Tue, 4 Jul 2023 16:31:51 +0100 (BST) From: =?iso-8859-1?Q?M=E5ns_Rullg=E5rd?= To: Daniel Thompson Cc: Lee Jones , Jingoo Han , Helge Deller , dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] backlight: led_bl: fix initial power state References: <20230704140750.25799-1-mans@mansr.com> <20230704150310.GA385243@aspen.lan> Date: Tue, 04 Jul 2023 16:31:51 +0100 In-Reply-To: <20230704150310.GA385243@aspen.lan> (Daniel Thompson's message of "Tue, 4 Jul 2023 16:03:10 +0100") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.2 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Daniel Thompson writes: > On Tue, Jul 04, 2023 at 03:07:50PM +0100, Mans Rullgard wrote: >> The condition for the initial power state based on the default >> brightness value is reversed. Fix it. >> >> Fixes: ae232e45acf9 ("backlight: add led-backlight driver") >> Signed-off-by: Mans Rullgard >> --- >> drivers/video/backlight/led_bl.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/video/backlight/led_bl.c b/drivers/video/backlight/led_bl.c >> index 3259292fda76..28e83618a296 100644 >> --- a/drivers/video/backlight/led_bl.c >> +++ b/drivers/video/backlight/led_bl.c >> @@ -200,8 +200,8 @@ static int led_bl_probe(struct platform_device *pdev) >> props.type = BACKLIGHT_RAW; >> props.max_brightness = priv->max_brightness; >> props.brightness = priv->default_brightness; >> - props.power = (priv->default_brightness > 0) ? FB_BLANK_POWERDOWN : >> - FB_BLANK_UNBLANK; >> + props.power = (priv->default_brightness > 0) ? FB_BLANK_UNBLANK : >> + FB_BLANK_POWERDOWN; > > The logic was wrong before but I think will still be wrong after the > change too (e.g. the bogus logic is probably avoiding backlight flicker > in some use cases). > > The logic here needs to be similar to what pwm_bl.c implements in > pwm_backlight_initial_power_state(). Whilst it might be better > to implement this in led_bl_get_leds() let me show what I mean > in code that fits in the current line: > > /* > * Activate the backlight if the LEDs are already lit *or* > * there is no phandle link (meaning the backlight power > * state cannot be synced with the display state). > */ > props.power = (active_at_boot || !dev->node->phandle) ? > FB_BLANK_UNBLANK : FB_BLANK_POWERDOWN; > > Note that active_at_boot is not the same as (priv->default_brightness > 0) > since the value read by led_bl_get_leds() can be clobbered when we > parse the properties. Am I understanding correctly that the code should be using the default_brightness value as set by led_bl_get_leds() to determine the initial power state, not whatever default value the devicetree provides? -- Måns Rullgård