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Wed, 30 Jan 2019 05:36:07 -0800 (PST) Received: from dell ([2.27.35.198]) by smtp.gmail.com with ESMTPSA id f191sm2268436wmg.12.2019.01.30.05.36.06 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 30 Jan 2019 05:36:06 -0800 (PST) Date: Wed, 30 Jan 2019 13:36:05 +0000 From: Lee Jones To: Chen-Yu Tsai Cc: Thierry Reding , Daniel Thompson , Jingoo Han , linux-pwm@vger.kernel.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, Maxime Ripard , linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH] backlight: pwm_bl: Use gpiod_get_value_cansleep() to get initial state Message-ID: <20190130133605.GI4701@dell> References: <20190127145054.3770-1-wens@csie.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190127145054.3770-1-wens@csie.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, 27 Jan 2019, Chen-Yu Tsai wrote: > gpiod_get_value() gives out a warning if access to the underlying gpiochip > requires sleeping, which is common for I2C based chips: > > WARNING: CPU: 0 PID: 77 at drivers/gpio/gpiolib.c:2500 gpiod_get_value+0xd0/0x100 > Modules linked in: > CPU: 0 PID: 77 Comm: kworker/0:2 Not tainted 4.14.0-rc3-00589-gf32897915d48-dirty #90 > Hardware name: Allwinner sun4i/sun5i Families > Workqueue: events deferred_probe_work_func > [] (unwind_backtrace) from [] (show_stack+0x10/0x14) > [] (show_stack) from [] (dump_stack+0x88/0x9c) > [] (dump_stack) from [] (__warn+0xe8/0x100) > [] (__warn) from [] (warn_slowpath_null+0x20/0x28) > [] (warn_slowpath_null) from [] (gpiod_get_value+0xd0/0x100) > [] (gpiod_get_value) from [] (pwm_backlight_probe+0x238/0x508) > [] (pwm_backlight_probe) from [] (platform_drv_probe+0x50/0xac) > [] (platform_drv_probe) from [] (driver_probe_device+0x238/0x2e8) > [] (driver_probe_device) from [] (bus_for_each_drv+0x44/0x94) > [] (bus_for_each_drv) from [] (__device_attach+0xb0/0x114) > [] (__device_attach) from [] (bus_probe_device+0x84/0x8c) > [] (bus_probe_device) from [] (deferred_probe_work_func+0x50/0x14c) > [] (deferred_probe_work_func) from [] (process_one_work+0x1ec/0x414) > [] (process_one_work) from [] (worker_thread+0x2b0/0x5a0) > [] (worker_thread) from [] (kthread+0x14c/0x154) > [] (kthread) from [] (ret_from_fork+0x14/0x24) > > This was missed in commit 0c9501f823a4 ("backlight: pwm_bl: Handle gpio > that can sleep"). The code was then moved to a separate function in > commit 7613c922315e ("backlight: pwm_bl: Move the checks for initial power > state to a separate function"). > > The only usage of gpiod_get_value() is during the probe stage, which is > safe to sleep in. Switch to gpiod_get_value_cansleep(). > > Fixes: 0c9501f823a4 ("backlight: pwm_bl: Handle gpio that can sleep") > Signed-off-by: Chen-Yu Tsai > --- > drivers/video/backlight/pwm_bl.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) Applied, thanks. -- Lee Jones [李琼斯] Linaro Services Technical Lead Linaro.org │ Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog