linux-kernel - Re: [PATCH v2 4/5] clk: cygnus: add clock support for Broadcom Cygnus

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Date:	Wed, 07 Jan 2015 10:11:38 +0100
From:	Arnd Bergmann <arnd@...db.de>
To:	Ray Jui <rjui@...adcom.com>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Mike Turquette <mturquette@...aro.org>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Matt Porter <mporter@...aro.org>,
	Alex Elder <elder@...aro.org>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Russell King <linux@....linux.org.uk>,
	devicetree@...r.kernel.org, Scott Branden <sbranden@...adcom.com>,
	linux-kernel@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: Re: [PATCH v2 4/5] clk: cygnus: add clock support for Broadcom Cygnus

On Tuesday 06 January 2015 18:29:07 Ray Jui wrote:
> On 1/6/2015 12:21 PM, Arnd Bergmann wrote:
> > On Monday 05 January 2015 15:21:15 Ray Jui wrote:
> > 
> > The tables look fairly regular. Is it possible that it's common
> > to all iproc variants with a standard way to derive all other
> > values from the channel index?
> > 
> Ah no. Not only it's different between different iproc variants, it's
> also different between plls on the same soc.

Ok, I see.
 
> >> +static const struct iproc_asiu_gate asiu_gate[BCM_CYGNUS_NUM_ASIU_CLKS] = {
> >> +	[BCM_CYGNUS_ASIU_KEYPAD_CLK] =
> >> +		asiu_gate_val(0x0, 7),
> >> +	[BCM_CYGNUS_ASIU_ADC_CLK] =
> >> +		asiu_gate_val(0x0, 9),
> >> +	[BCM_CYGNUS_ASIU_PWM_CLK] =
> >> +		asiu_gate_val(IPROC_CLK_INVALID_OFFSET, 0),
> >> +};
> > 
> > Here I think a better binding would be to pass the gate value in the
> > clock specifier, rather than an artificial index. That would let
> > you get rid of the BCM_CYGNUS_ASIU_KEYPAD_CLK/BCM_CYGNUS_ASIU_ADC_CLK
> > macros.
> > 
> You meant to pass in both the gate register offset and its bit shift
> through the clock specifier? But isn't the current ASIU clock code much
> more consistent with the rest of the iProc clock code?

For simple devices that don't need an index macro, I would always
prefer not defining them, because they are a pain to maintain.
For a simple gate clock controller, we could compute both the offset
and bit number from a single integer.

However, I now saw upon taking a closer look that the asiu has both
a gate and a divider, and the latter one is not as simple, so
my comment doesn't apply here.

	Arnd
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