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From: Banajit Goswami <banajit.goswami@gmail.com>
To: jg1.han@samsung.com
Cc: linux-samsung-soc@vger.kernel.org,
	Ben Dooks <ben-linux@fluff.org>,
	linux-arm-kernel@lists.infradead.org, kgene.kim@samsung.com
Subject: Re: [PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung SMDKV310
Date: Thu, 23 Jun 2011 15:42:09 +0530	[thread overview]
Message-ID: <BANLkTikb33PCQtiVmcVm38-ptZPMXMk60g@mail.gmail.com> (raw)
In-Reply-To: <BANLkTi=SqB7NHQ7vStegFgQjihoQRmzVCw@mail.gmail.com>

> 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

WARNING: multiple messages have this Message-ID (diff)
From: banajit.goswami@gmail.com (Banajit Goswami)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung SMDKV310
Date: Thu, 23 Jun 2011 15:42:09 +0530	[thread overview]
Message-ID: <BANLkTikb33PCQtiVmcVm38-ptZPMXMk60g@mail.gmail.com> (raw)
In-Reply-To: <BANLkTi=SqB7NHQ7vStegFgQjihoQRmzVCw@mail.gmail.com>

> 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

  parent reply	other threads:[~2011-06-23 10:12 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-06-22  6:56 [PATCH] ARM: EXYNOS4: Add PWM backlight support on Samsung SMDKV310 JinGoo Han
     [not found] ` <BANLkTi=SqB7NHQ7vStegFgQjihoQRmzVCw@mail.gmail.com>
2011-06-23 10:12   ` Banajit Goswami [this message]
2011-06-23 10:12     ` Banajit Goswami
2011-06-23 11:44     ` Kukjin Kim
2011-06-23 11:44       ` Kukjin Kim
2011-06-23 13:53       ` Banajit Goswami
2011-06-23 13:53         ` Banajit Goswami
  -- strict thread matches above, loose matches on Subject: below --
2011-06-22  6:41 Banajit Goswami
2011-06-22  6:41 ` Banajit Goswami

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