From mboxrd@z Thu Jan 1 00:00:00 1970 From: Lukasz Majewski Subject: Re: [PATCH v2 RESEND] video: backlight: pwm_bl: Initialize fb_bl_on[x] and use_count during pwm_backlight_probe() Date: Fri, 13 Jan 2017 01:27:37 +0100 Message-ID: <20170113012737.45f5a3db@jawa> References: <1477169904-14997-1-git-send-email-l.majewski@majess.pl> <1482790896-29202-1-git-send-email-l.majewski@majess.pl> <20170103083032.GA2977@dell> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Return-path: Received: from mail-out.m-online.net ([212.18.0.10]:59981 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750760AbdAMA1l (ORCPT ); Thu, 12 Jan 2017 19:27:41 -0500 In-Reply-To: <20170103083032.GA2977@dell> Sender: linux-pwm-owner@vger.kernel.org List-Id: linux-pwm@vger.kernel.org To: Thierry Reding , Jingoo Han Cc: Lee Jones , linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Liu Ying , Fabio Estevam , Fabio Estevam , Tomi Valkeinen , l.majewski@majess.pl Dear All, > Thierry, Jingoo, > > Please respond to Lukasz. Yes, your response is more than welcome....... :-) Thanks in advance, Łukasz Majewski > > On Mon, 26 Dec 2016, Lukasz Majewski wrote: > > > The commit a55944ca82d2 > > ("backlight: update bd state & fb_blank properties when necessary") > > has posed some extra restrictions on blanking and unblanking frame > > buffer device. > > > > Unfortunately, pwm_bl driver's probe did not initialize members of > > struct backlight_device necessary for further blank/unblank > > operation. > > > > This code in case of initial unblank of backlight device (default > > behaviour) sets use_count to 1 and marks this particular backlight > > device as used by all available fb devices (since it is not known > > during probe how much and which fb devices will be assigned). > > > > Without this code, the backlight works properly until one tries to > > blank it manually from sysfs with "echo 1 > > > /sys/class/graphics/fb0/blank". Since fb_bl_on[0] and use_count > > > were both set to 0, the logic at > > fb_notifier_callback (@backlight.c) thought that we didn't turn on > > (unblanked) the backlight device and refuses to disable (blank) it. > > As a result we see garbage from fb displayed. > > > > Signed-off-by: Lukasz Majewski > > --- > > The patch has been tested on i.MX6q with vanilla 4.9 kernel. > > It applies on 4.10-rc1. > > --- > > drivers/video/backlight/pwm_bl.c | 10 +++++++++- > > 1 file changed, 9 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/video/backlight/pwm_bl.c > > b/drivers/video/backlight/pwm_bl.c index 1261400..6859ba0 100644 > > --- a/drivers/video/backlight/pwm_bl.c > > +++ b/drivers/video/backlight/pwm_bl.c > > @@ -202,7 +202,7 @@ static int pwm_backlight_probe(struct > > platform_device *pdev) struct pwm_bl_data *pb; > > int initial_blank = FB_BLANK_UNBLANK; > > struct pwm_args pargs; > > - int ret; > > + int ret, i; > > > > if (!data) { > > ret = pwm_backlight_parse_dt(&pdev->dev, &defdata); > > @@ -348,6 +348,14 @@ static int pwm_backlight_probe(struct > > platform_device *pdev) > > bl->props.brightness = data->dft_brightness; > > bl->props.power = initial_blank; > > + > > + if (initial_blank == FB_BLANK_UNBLANK) { > > + for (i = 0; i < FB_MAX; i++) > > + bl->fb_bl_on[i] = true; > > + > > + bl->use_count = 1; > > + } > > + > > backlight_update_status(bl); > > > > platform_set_drvdata(pdev, bl); > Best regards, Lukasz Majewski -- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-10 Fax: (+49)-8142-66989-80 Email: wd@denx.de