From mboxrd@z Thu Jan  1 00:00:00 1970
From: Banajit Goswami <banajit.goswami@gmail.com>
Subject: Re: [PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung SMDKV310
Date: Thu, 23 Jun 2011 15:42:09 +0530
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> From: JinGoo Han <jg1.han@samsung.com>
>
> Hi, Banajit.
Hi Jingoo,

>>
>> Signed-off-by: Banajit Goswami <banajit.g@samsung.com>
>> ---
=2E..
<snip>
=2E..
>> + =C2=A0 =C2=A0 .pwm_period_ns =C2=A0=3D 78770,
> Please use 1000 as pwm_period_ns instead of 78770 as follows:
> - =C2=A0 =C2=A0 =C2=A0 .pwm_period_ns =C2=A0=3D 78770,
> + =C2=A0 =C2=A0 =C2=A0 .pwm_period_ns =C2=A0=3D 1000,
>
Yes, I will modify the period value and send updated patch

> The value '78770' makes noise related to resonance at LCD board.
>
> I will explain how I get the value of PWM period.
>
> The SMDK boards use LT3591 as backlight LED driver of LTE480WV LCD
> According to the LT3591 datasheet, the switching frequency should
> be 1MHz. So, PWM period is calculated by following formula:
> =C2=A0 =C2=A0 =C2=A0 =C2=A0PWM period =3D 1/switching frequency
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =3D 1/1MHz
> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0=
 =C2=A0 =3D 1000 ns
>
Thanks for the explanation.

> You can find LT3591 datasheet easily on the Internet. Please refer to=
 it
> for more information.
> Good luck.
Thanks you.

>> + =C2=A0 =C2=A0 .init =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =3D smdkv31=
0_backlight_init,
=2E..
<snip>
=2E..
>

Regards,
Banajit

From mboxrd@z Thu Jan  1 00:00:00 1970
From: banajit.goswami@gmail.com (Banajit Goswami)
Date: Thu, 23 Jun 2011 15:42:09 +0530
Subject: [PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung
	SMDKV310
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	<BANLkTi=SqB7NHQ7vStegFgQjihoQRmzVCw@mail.gmail.com>
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> From: JinGoo Han <jg1.han@samsung.com>
>
> Hi, Banajit.
Hi Jingoo,

>>
>> Signed-off-by: Banajit Goswami <banajit.g@samsung.com>
>> ---
...
<snip>
...
>> + ? ? .pwm_period_ns ?= 78770,
> Please use 1000 as pwm_period_ns instead of 78770 as follows:
> - ? ? ? .pwm_period_ns ?= 78770,
> + ? ? ? .pwm_period_ns ?= 1000,
>
Yes, I will modify the period value and send updated patch

> The value '78770' makes noise related to resonance at LCD board.
>
> I will explain how I get the value of PWM period.
>
> The SMDK boards use LT3591 as backlight LED driver of LTE480WV LCD
> According to the LT3591 datasheet, the switching frequency should
> be 1MHz. So, PWM period is calculated by following formula:
> ? ? ? ?PWM period = 1/switching frequency
> ? ? ? ? ? ? ? ? ? ? ? = 1/1MHz
> ? ? ? ? ? ? ? ? ? ? ? = 1000 ns
>
Thanks for the explanation.

> You can find LT3591 datasheet easily on the Internet. Please refer to it
> for more information.
> Good luck.
Thanks you.

>> + ? ? .init ? ? ? ? ? = smdkv310_backlight_init,
...
<snip>
...
>

Regards,
Banajit