linux-kernel - Re: [PATCH 2/7] ARM: bcm2835: Add a Raspberry Pi-specific clock driver.

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Message-ID: <87mw0ncia2.fsf@eliezer.anholt.net>
Date:	Fri, 29 May 2015 12:09:41 -0700
From:	Eric Anholt <eric@...olt.net>
To:	Stephen Warren <swarren@...dotorg.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	linux-rpi-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Lee Jones <lee@...nel.org>, devicetree@...r.kernel.org,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>
Subject: Re: [PATCH 2/7] ARM: bcm2835: Add a Raspberry Pi-specific clock driver.

Stephen Warren <swarren@...dotorg.org> writes:

> On 05/18/2015 01:43 PM, Eric Anholt wrote:
>> +	init.flags = CLK_IS_ROOT;
>
> Is it possible to add clock parent information to the driver, so the
> clocks are all hooked together into the correct tree, rather than all
> looking like root clocks?
>
> One of the many reasons I didn't do anything FW-wise for the kernel was
> the hope that such information would be forthcoming, and hence we could
> have complete kernel drivers.

As far as I can tell, none of these clocks are the parent of any other.

There's a layer of PLLs, then clockman almost always just dividing off
of those.  In response to a clockman request (which is what this
property tag quickly maps to), only PLLH ever gets changed as a result
of RPI_CLOCK_PIXEL.  PLLH feeds the HDMI and VEC (SDTV).  We don't have
an SDTV clock for us to control through these interfaces, so there are
no conflicts that I can see.  Only two clockman clocks I see divide off
of on other clockman clocks, and we don't have access to those.

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