linux-kernel - Re: [PATCH] ARM: davinci: dm644x: fix out range signal for ED

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Message-ID: <CA+V-a8uqQhpe+9Q_A_ojR1MahHLnbKpOEBdg9Vz3Gq8YQbHyjg@mail.gmail.com>
Date:	Thu, 4 Oct 2012 19:23:26 +0530
From:	Prabhakar Lad <prabhakar.csengg@...il.com>
To:	Sekhar Nori <nsekhar@...com>
Cc:	DLOS <davinci-linux-open-source@...ux.davincidsp.com>,
	Manjunath Hadli <manjunath.hadli@...com>,
	VGER <linux-kernel@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"Lad, Prabhakar" <prabhakar.lad@...com>
Subject: Re: [PATCH] ARM: davinci: dm644x: fix out range signal for ED

Sekhar

On Thu, Oct 4, 2012 at 12:43 PM, Sekhar Nori <nsekhar@...com> wrote:
> On 10/4/2012 10:22 AM, Prabhakar Lad wrote:
>> Hi Sekhar,
>>
>> On Wed, Oct 3, 2012 at 4:08 PM, Sekhar Nori <nsekhar@...com> wrote:
>>> On 10/3/2012 12:05 PM, Prabhakar wrote:
>>>> From: Lad, Prabhakar <prabhakar.lad@...com>
>>>>
>>>> while testing display on dm644x, for ED out-range signals
>>>> was observed. This patch fixes appropriate clock setting
>>>> for ED.
>>>
>>> Can you please clarify what you mean by "out range signal"? Are there
>>> any user visible artifacts on the display? What was the clock being
>>> provided earlier and what is the value after this patch?
>>>
>>> Also, is the issue severe enough that this patch should be applied to
>>> stable tree as well?
>>>
>> Ideally a clock of 54Mhz is required for  enhanced definition to
>> work, which it was actually set to but while testing I noticed
>> out-of-range signal. The out-of-range signal is often caused
>> when the field rate is above the rate that the television will handle.
>> When this is the case the TV or monitor displays "Out-Of-Range Signal".
>>
>> Reducing the clock fixed it. now the clock is set to 27Mhz.
>
> So, is the requirement for ED 54MHz or lower? Still trying to explain
> myself how 27MHz is working where a 54MHz is required. I guess there is
> also a lower limit on what the frequency should be?
>
Ideally its 54Mhz, but I see in the datasheet for AD7342/3 [1] it can also
work at 27Mhz too.

Regards,
--Prabhakar

[1] http://www.analog.com/static/imported-files/data_sheets/ADV7342_7343.pdf

> Sorry I am not familiar will all the video concepts, hence the questions.
>
> Thanks,
> Sekhar
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