From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robert Jarzmik Date: Sat, 25 Aug 2018 08:04:10 +0000 Subject: Re: [PATCH] backlight: pwm_bl: Fix brightness levels for non-DT case. Message-Id: <87h8ji98jp.fsf@belgarion.home> List-Id: References: <20180824155402.2822-1-enric.balletbo@collabora.com> In-Reply-To: <20180824155402.2822-1-enric.balletbo@collabora.com> (Enric Balletbo i. Serra's message of "Fri, 24 Aug 2018 17:54:02 +0200") MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Enric Balletbo i Serra Cc: linux-kernel@vger.kernel.org, daniel.thompson@linaro.org, lee.jones@linaro.org, kernel@collabora.com, heiko@sntech.de, linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org, Thierry Reding , Bartlomiej Zolnierkiewicz , dri-devel@lists.freedesktop.org, Jingoo Han Enric Balletbo i Serra writes: > Commit '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED > linearly to human eye")' allows the possibility to compute a default > brightness table when there isn't the brightness-levels property in the > DT. Unfortunately the changes made broke the pwm backlight for the > non-DT boards. > > Usually, the non-DT boards don't pass the brightness levels via platform > data, instead, they set the max_brightness in their platform data and the > driver calculates the level without a table. The ofending patch assumed > that when there is no brightness levels table we should create one, but this > is clearly wrong for the non-DT case. > > After this patch the code handles the DT and the non-DT case taking in > consideration also if max_brightness is set or not. The default table is > only created when neither, brightness-levels and max_brightness, are > set. > > The patch also fixes another issue found by Robert. Before this patch > looks like a division by 0 was possible when state.period returned 0 by > pwm_get_state(). This is because pwm_get_state() was called before > pwm_apply_args() so state.period was not initialized. The patch moves > the pwm_apply_args() call before any call to pwm_get_state(). > > Fixes: '88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")' > Reported-by: Robert Jarzmik > Signed-off-by: Enric Balletbo i Serra Tested-by: Robert Jarzmik Cheers. -- Robert