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([2a01:110f:b59:fd00:9c13:a547:3fe2:ec95]) by smtp.gmail.com with ESMTPSA id j89sm7698816edb.20.2020.07.01.14.28.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 01 Jul 2020 14:28:33 -0700 (PDT) Subject: Re: [PATCH] leds: core: Use blocking op for system suspend To: Kai-Heng Feng , pavel@ucw.cz Cc: anthony.wong@canonical.com, Dan Murphy , "open list:LED SUBSYSTEM" , open list References: <20200701093541.14191-1-kai.heng.feng@canonical.com> From: Jacek Anaszewski Message-ID: <38622f5a-4518-cdb4-d1ca-581f470ce797@gmail.com> Date: Wed, 1 Jul 2020 23:28:29 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200701093541.14191-1-kai.heng.feng@canonical.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-leds-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-leds@vger.kernel.org Hi Kai-Heng, Thank you for the patch. On 7/1/20 11:35 AM, Kai-Heng Feng wrote: > Sometimes LED won't be turned off by LED_CORE_SUSPENDRESUME flag upon > system suspend. Just out of curiosity - are you experiencing that on some hardware? > led_set_brightness_nopm() uses schedule_work() to set LED brightness. > However, there's no guarantee that the scheduled work gets executed > because no one calls flush_scheduled_work(). > > As flush_scheduled_work() may affect other drivers' suspend routines, > take a more contained approach which uses blocking op to make sure the > LED gets turned off. > > Signed-off-by: Kai-Heng Feng > --- > drivers/leds/led-core.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/drivers/leds/led-core.c b/drivers/leds/led-core.c > index f1f718dbe0f8..9a5bfcd7a704 100644 > --- a/drivers/leds/led-core.c > +++ b/drivers/leds/led-core.c > @@ -269,6 +269,11 @@ EXPORT_SYMBOL_GPL(led_set_brightness); > void led_set_brightness_nopm(struct led_classdev *led_cdev, > enum led_brightness value) > { > + > + if (led_cdev->flags & LED_SUSPENDED && > + !__led_set_brightness_blocking(led_cdev, value)) > + return; > + This function is "nopm" for a reason - we do not make here any pm management related operations. Instead of that, please just add flush_work(&led_cdev->set_brightness_work); at the end of led_classdev_suspend() in drivers/leds/led-class.c. -- Best regards, Jacek Anaszewski