linux-kernel - Re: [PATCH v3 01/11] clk: davinci

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Message-ID: <5092568C.5000805@ti.com>
Date:	Thu, 1 Nov 2012 16:31:32 +0530
From:	Sekhar Nori <nsekhar@...com>
To:	Murali Karicheri <m-karicheri2@...com>
CC:	<mturquette@...aro.org>, <arnd@...db.de>,
	<akpm@...ux-foundation.org>, <shawn.guo@...aro.org>,
	<rob.herring@...xeda.com>, <linus.walleij@...aro.org>,
	<viresh.linux@...il.com>, <linux-kernel@...r.kernel.org>,
	<khilman@...com>, <linux@....linux.org.uk>, <sshtylyov@...sta.com>,
	<davinci-linux-open-source@...ux.davincidsp.com>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-keystone@...t.ti.com>
Subject: Re: [PATCH v3 01/11] clk: davinci - add main PLL clock driver

On 10/31/2012 7:16 PM, Murali Karicheri wrote:
> On 10/31/2012 08:29 AM, Sekhar Nori wrote:

>>> +    /*
>>> +     * if fixed_multiplier is non zero, multiply pllm value by this
>>> +     * value.
>>> +     */
>>> +    if (pll_data->fixed_multiplier)
>>> +        mult =  pll_data->fixed_multiplier *
>>> +                (mult & pll_data->pllm_mask);
>>> +    else
>>> +        mult = (mult & pll_data->pllm_mask) + 1;
>> Hmm, this is interpreting the 'mult' register field differently in both
>> cases. In one case it is 'actual multiplier - 1' and in other case it is
>> the 'actual multiplier' itself. Can we be sure that the mult register
>> definition will change whenever there is a fixed multiplier in the PLL
>> block? I don't think any of the existing DaVinci devices have a fixed
>> multiplier. Is this on keystone?
> Read section 6.4.3 (PLL Mode) in DM365 documentation (SPRUFG5a.pdf) that
> states PLL multiplies the clock by 2x the value in the PLLM. In the old
> code this is handled by a if cpu_is_* macro that we can't use in the
> driver. So this is represented by a fixed_multiplier that can be set to
> 2 for DM365 and zero on other SoCs.

Thanks for the clarification.

Regards,
Sekhar
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