From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: "Lothar Waßmann" <LW@KARO-electronics.de>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Jingoo Han" <jingoohan1@gmail.com>,
"Lee Jones" <lee.jones@linaro.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pwm@vger.kernel.org
Subject: Re: [PATCH] backlight: pwm_bl: disable PWM when 'duty_cycle' is zero
Date: Mon, 06 Jun 2016 12:02:21 +0000 [thread overview]
Message-ID: <5755664D.5070109@ti.com> (raw)
In-Reply-To: <1465209896-10319-1-git-send-email-LW@KARO-electronics.de>
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Hi,
On 06/06/16 13:44, Lothar Waßmann wrote:
> 'brightness' is usually an index into a table of duty_cycle values,
> where the value at index 0 may well be non-zero
> (tegra30-apalis-eval.dts and tegra30-colibri-eval-v3.dts are real-life
> examples).
> Thus brightness == 0 does not necessarily mean that the PWM output
> will be inactive.
> Check for 'duty_cycle == 0' rather than 'brightness == 0' to decide
> whether to disable the PWM.
The binding doc does say:
- brightness-levels: Array of distinct brightness levels. Typically these
are in the range from 0 to 255, but any range starting at 0 will do.
The actual brightness level (PWM duty cycle) will be interpolated
from these values. 0 means a 0% duty cycle (darkest/off), while the
last value in the array represents a 100% duty cycle (brightest).
Tomi
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WARNING: multiple messages have this Message-ID (diff)
From: Tomi Valkeinen <tomi.valkeinen@ti.com>
To: "Lothar Waßmann" <LW@KARO-electronics.de>,
"Jean-Christophe Plagniol-Villard" <plagnioj@jcrosoft.com>,
"Jingoo Han" <jingoohan1@gmail.com>,
"Lee Jones" <lee.jones@linaro.org>,
"Thierry Reding" <thierry.reding@gmail.com>,
linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pwm@vger.kernel.org
Subject: Re: [PATCH] backlight: pwm_bl: disable PWM when 'duty_cycle' is zero
Date: Mon, 6 Jun 2016 15:02:21 +0300 [thread overview]
Message-ID: <5755664D.5070109@ti.com> (raw)
In-Reply-To: <1465209896-10319-1-git-send-email-LW@KARO-electronics.de>
[-- Attachment #1.1: Type: text/plain, Size: 869 bytes --]
Hi,
On 06/06/16 13:44, Lothar Waßmann wrote:
> 'brightness' is usually an index into a table of duty_cycle values,
> where the value at index 0 may well be non-zero
> (tegra30-apalis-eval.dts and tegra30-colibri-eval-v3.dts are real-life
> examples).
> Thus brightness == 0 does not necessarily mean that the PWM output
> will be inactive.
> Check for 'duty_cycle == 0' rather than 'brightness == 0' to decide
> whether to disable the PWM.
The binding doc does say:
- brightness-levels: Array of distinct brightness levels. Typically these
are in the range from 0 to 255, but any range starting at 0 will do.
The actual brightness level (PWM duty cycle) will be interpolated
from these values. 0 means a 0% duty cycle (darkest/off), while the
last value in the array represents a 100% duty cycle (brightest).
Tomi
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next prev parent reply other threads:[~2016-06-06 12:02 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-06 10:44 [PATCH] backlight: pwm_bl: disable PWM when 'duty_cycle' is zero Lothar Waßmann
2016-06-06 10:44 ` Lothar Waßmann
2016-06-06 12:02 ` Tomi Valkeinen [this message]
2016-06-06 12:02 ` Tomi Valkeinen
2016-06-07 6:49 ` Lothar Waßmann
2016-06-07 6:49 ` Lothar Waßmann
2016-06-07 6:49 ` Lothar Waßmann
2016-06-07 8:02 ` Tomi Valkeinen
2016-06-07 8:02 ` Tomi Valkeinen
2016-06-07 8:02 ` Tomi Valkeinen
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