From: Pavel Machek <pavel@ucw.cz>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org,
Daniel Thompson <daniel.thompson@linaro.org>,
Douglas Anderson <dianders@chromium.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Jingoo Han <jingoohan1@gmail.com>,
Brian Norris <briannorris@chromium.org>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-pwm@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Thierry Reding <thierry.reding@gmail.com>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
linux-fbdev@vger.kernel.org,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
Lee Jones <lee.jones@linaro.org>,
linux-leds@vger.kernel.org
Subject: Re: [PATCH 2/2] backlight: pwm_bl: Get number of brightness levels for CIE 1931 from the device tree
Date: Tue, 11 Jun 2019 12:18:43 +0200 [thread overview]
Message-ID: <20190611101843.GD7526@amd> (raw)
In-Reply-To: <20190610233739.29477-2-mka@chromium.org>
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On Mon 2019-06-10 16:37:39, Matthias Kaehlcke wrote:
> Commit 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
> linearly to human eye") uses pwm_period / hweight32(pwm_period) as
> as heuristic to determine the number of brightness levels when the DT
> doesn't provide a brightness level table. This heuristic is broken
> and can result in excessively large brightness tables.
>
> Instead of using the heuristic try to retrieve the number of
> brightness levels from the device tree (property 'max-brightness'
> + 1). If the value is not specified use a default of 256 levels.
>
> Fixes: 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
I don't think this one is suitable for stable. I'm pretty sure the
heuristics works well for many boards, and you just replaced it with
another heuristics ("256").
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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WARNING: multiple messages have this Message-ID (diff)
From: Pavel Machek <pavel@ucw.cz>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Lee Jones <lee.jones@linaro.org>,
Daniel Thompson <daniel.thompson@linaro.org>,
Jingoo Han <jingoohan1@gmail.com>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Thierry Reding <thierry.reding@gmail.com>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
dri-devel@lists.freedesktop.org, linux-leds@vger.kernel.org,
devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pwm@vger.kernel.org, linux-fbdev@vger.kernel.org,
Douglas Anderson <dianders@chromium.org>,
Brian Norris <briannorris@chromium.org>
Subject: Re: [PATCH 2/2] backlight: pwm_bl: Get number of brightness levels for CIE 1931 from the device tree
Date: Tue, 11 Jun 2019 12:18:43 +0200 [thread overview]
Message-ID: <20190611101843.GD7526@amd> (raw)
In-Reply-To: <20190610233739.29477-2-mka@chromium.org>
[-- Attachment #1: Type: text/plain, Size: 1106 bytes --]
On Mon 2019-06-10 16:37:39, Matthias Kaehlcke wrote:
> Commit 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
> linearly to human eye") uses pwm_period / hweight32(pwm_period) as
> as heuristic to determine the number of brightness levels when the DT
> doesn't provide a brightness level table. This heuristic is broken
> and can result in excessively large brightness tables.
>
> Instead of using the heuristic try to retrieve the number of
> brightness levels from the device tree (property 'max-brightness'
> + 1). If the value is not specified use a default of 256 levels.
>
> Fixes: 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
I don't think this one is suitable for stable. I'm pretty sure the
heuristics works well for many boards, and you just replaced it with
another heuristics ("256").
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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WARNING: multiple messages have this Message-ID (diff)
From: Pavel Machek <pavel@ucw.cz>
To: Matthias Kaehlcke <mka@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org,
Daniel Thompson <daniel.thompson@linaro.org>,
Douglas Anderson <dianders@chromium.org>,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Jingoo Han <jingoohan1@gmail.com>,
Brian Norris <briannorris@chromium.org>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
linux-pwm@vger.kernel.org, Rob Herring <robh+dt@kernel.org>,
Thierry Reding <thierry.reding@gmail.com>,
Jacek Anaszewski <jacek.anaszewski@gmail.com>,
linux-fbdev@vger.kernel.org,
Enric Balletbo i Serra <enric.balletbo@collabora.com>,
Lee Jones <lee.jones@linaro.org>,
linux-leds@vger.kernel.org
Subject: Re: [PATCH 2/2] backlight: pwm_bl: Get number of brightness levels for CIE 1931 from the device tree
Date: Tue, 11 Jun 2019 10:18:43 +0000 [thread overview]
Message-ID: <20190611101843.GD7526@amd> (raw)
In-Reply-To: <20190610233739.29477-2-mka@chromium.org>
[-- Attachment #1: Type: text/plain, Size: 1106 bytes --]
On Mon 2019-06-10 16:37:39, Matthias Kaehlcke wrote:
> Commit 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED
> linearly to human eye") uses pwm_period / hweight32(pwm_period) as
> as heuristic to determine the number of brightness levels when the DT
> doesn't provide a brightness level table. This heuristic is broken
> and can result in excessively large brightness tables.
>
> Instead of using the heuristic try to retrieve the number of
> brightness levels from the device tree (property 'max-brightness'
> + 1). If the value is not specified use a default of 256 levels.
>
> Fixes: 88ba95bedb79 ("backlight: pwm_bl: Compute brightness of LED linearly to human eye")
I don't think this one is suitable for stable. I'm pretty sure the
heuristics works well for many boards, and you just replaced it with
another heuristics ("256").
> Signed-off-by: Matthias Kaehlcke <mka@chromium.org>
Acked-by: Pavel Machek <pavel@ucw.cz>
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2019-06-11 10:18 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-10 23:37 [PATCH 1/2] dt-bindings: pwm-backlight: Add 'max-brightness' property Matthias Kaehlcke
2019-06-10 23:37 ` Matthias Kaehlcke
2019-06-10 23:37 ` [PATCH 2/2] backlight: pwm_bl: Get number of brightness levels for CIE 1931 from the device tree Matthias Kaehlcke
2019-06-10 23:37 ` Matthias Kaehlcke
2019-06-11 10:18 ` Pavel Machek [this message]
2019-06-11 10:18 ` Pavel Machek
2019-06-11 10:18 ` Pavel Machek
2019-06-11 21:58 ` Matthias Kaehlcke
2019-06-11 21:58 ` Matthias Kaehlcke
2019-06-11 15:33 ` Daniel Thompson
2019-06-11 15:33 ` Daniel Thompson
2019-06-11 15:33 ` Daniel Thompson
2019-06-11 17:01 ` Matthias Kaehlcke
2019-06-11 17:01 ` Matthias Kaehlcke
2019-06-11 10:14 ` [PATCH 1/2] dt-bindings: pwm-backlight: Add 'max-brightness' property Pavel Machek
2019-06-11 10:14 ` Pavel Machek
2019-06-11 10:28 ` Thierry Reding
2019-06-11 10:28 ` Thierry Reding
2019-06-11 21:38 ` Matthias Kaehlcke
2019-06-11 21:38 ` Matthias Kaehlcke
2019-06-11 20:02 ` Jacek Anaszewski
2019-06-11 20:02 ` Jacek Anaszewski
2019-06-11 22:11 ` Matthias Kaehlcke
2019-06-11 22:11 ` Matthias Kaehlcke
-- strict thread matches above, loose matches on Subject: below --
2017-06-28 11:16 [PATCH 1/2] dt-bindings: pwm-backlight: Add pwm-delay-us property Enric Balletbo i Serra
2017-06-28 11:16 ` Enric Balletbo i Serra
2017-06-28 11:16 ` [PATCH 2/2] pwm-backlight: Add support for " Enric Balletbo i Serra
2017-06-28 11:16 ` Enric Balletbo i Serra
2017-06-28 13:16 ` [PATCH 1/2] dt-bindings: pwm-backlight: Add " Daniel Thompson
2017-06-28 13:16 ` Daniel Thompson
2017-06-28 13:30 ` Pavel Machek
2017-06-28 13:30 ` Pavel Machek
2017-06-28 14:15 ` Enric Balletbo Serra
2017-06-28 14:15 ` Enric Balletbo Serra
2017-06-29 13:07 ` Daniel Thompson
2017-06-29 13:07 ` Daniel Thompson
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