[PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung SMDKV310

[Banajit Goswami]

> From: JinGoo Han <jg1.han at samsung.com>
>
> Hi, Banajit.
Hi Jingoo,

>>
>> Signed-off-by: Banajit Goswami <banajit.g at samsung.com>
>> ---
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>> +     .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,
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>

Regards,
Banajit