linux-kernel - Re: [PATCH v2] clk: Add support for rate table based dividers

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Message-ID: <20120627162851.GT1623@pengutronix.de>
Date:	Wed, 27 Jun 2012 18:28:51 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Rajendra Nayak <rnayak@...com>
Cc:	mturquette@...com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, Sascha Hauer <kernel@...gutronix.de>,
	Viresh Kumar <viresh.linux@...il.com>
Subject: Re: [PATCH v2] clk: Add support for rate table based dividers

On Wed, Jun 27, 2012 at 04:31:33PM +0530, Rajendra Nayak wrote:
> Some divider clks do not have any obvious relationship
> between the divider and the value programmed in the
> register. For instance, say a value of 1 could signify divide
> by 6 and a value of 2 could signify divide by 4 etc.
> Also there are dividers where not all values possible
> based on the bitfield width are valid. For instance
> a 3 bit wide bitfield can be used to program a value
> from 0 to 7. However its possible that only 0 to 4
> are valid values.
> 
> All these cases need the platform code to pass a simple
> table of divider/value tuple, so the framework knows
> the exact value to be written based on the divider
> calculation and can also do better error checking.
> 
> This patch adds support for such rate table based
> dividers.
> 
> Also since this means adding a new parameter to the
> clk_register_divider(), update all existing users of
> it.

I'm not sure whether we should overload the divider code with another
type of divider. Maybe it would be better to add a new
clk-divider-table.c for this? Just an idea, the result may or may not be
better.

Sascha


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