linux-kernel - Re: [PATCH 0/5] clk: rockchip: add full support for HDMI clock on rk3288

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Message-ID: <54647142.4080800@rock-chips.com>
Date:	Thu, 13 Nov 2014 16:52:18 +0800
From:	Kever Yang <kever.yang@...k-chips.com>
To:	Heiko Stübner <heiko@...ech.de>
CC:	Mike Turquette <mturquette@...aro.org>, dianders@...omium.org,
	sonnyrao@...omium.org, addy.ke@...k-chips.com, cf@...k-chips.com,
	fzf@...k-chips.com, ykk@...k-chips.com, yzq@...k-chips.com,
	dkl@...k-chips.com, huangtao@...k-chips.com,
	linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] clk: rockchip: add full support for HDMI clock on
 rk3288

Hi Heiko,

On 11/07/2014 05:06 AM, Heiko Stübner wrote:
> Hi Kever,
>
> Am Dienstag, 4. November 2014, 15:52:34 schrieb Kever Yang:
>> we are going to make a clock usage solution for rk3288:
>> 1. CPLL and GPLL always not change after assign init;
>> 2. NPLL default as 500MHz, may used for most scene;
>> 3. NPLL may be changed by VOP(HDMI) clock for some special
>>     frequency requirement.
>>
>>      I test it with rk3288 evb on top of Heiko's clk-for-next
> In general I'm not really sure if allowing one component to arbitarily change
> a shared clock wouldn't result in trouble.
>
> At the moment only dclk_vop0 is included in your series, while the hdmi
> controller can connect to both vop0 and vop1.
> And as Doug mentioned the gpu also has the npll as one possible source.
I think the problem GPU HANGs with 480MHz clock from usbphy has
been fixed with my patch to gerrit:
https://chromium-review.googlesource.com/#/c/229554/
>
> Looking through the clock-tree there are a lot more components possibly using
> (or wanting to use) the npll: of course the VOPs, the edp, hdmi, isp, hevc,
> gpu, tsp uart0 and gmac. So I'm slightly uncomfortable with somehow reserving
> the npll for VOP0 alone.
It's true that I customized the usage of npll for VOP0 when we need some
very special frequency, but it doesn't means other modules can't use the
npll, it will always decided by clock core for module clocks that which 
parent
is the best.

I'll be very happy if there is a better solution for this situation, and any
suggestion is welcome.

- Kever
>
> But I also don't see a different way to get these frequencies right now.
>
>
> Heiko
>
>
>

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