From: slash.tmp@free•fr (Mason)
To: linux-arm-kernel@lists•infradead.org
Subject: Common/typical fractional divider HW API
Date: Fri, 5 Feb 2016 17:29:35 +0100 [thread overview]
Message-ID: <56B4CDEF.3080606@free.fr> (raw)
In-Reply-To: <1454688729.31169.87.camel@linux.intel.com>
On 05/02/2016 17:12, Andy Shevchenko wrote:
> On Fri, 2016-02-05 at 17:01 +0100, Mason wrote:
>
>> So, do you agree that
>>
>> DIV = 2^I * (1 + F/256)
>>
>> gives a more useful DIV distribution than
>>
>> DIV = I + F/16
>
> If you can change hardware why not to use any existing approach which
> suits better to your device?
Sorry, I don't understand the question.
In this part of my message, I was trying to argue that one HW API
"2^I * (1 + F/256)" seemed better than another one "I + F/16" on
any hardware.
> I don't remember any existing, though I didn't check much, divider
> register which takes something like that.
IIUC, you are saying that you've never seen hardware use the
"2^I * (1 + F/256)" formula, is that correct?
>> I'm not sure how to parse that. I'm using the divider driver
>> for a CPU clock, to do D(V)FS in cpufreq.
>
> If you are using custom stuff for custom hardware, I hope it's okay.
> But if we are talking about generic solutions (like clk-fractional-
> divider), I would suggest to consider existing users / hardware.
Are you saying that I could use the clk-fractional-divider with
hardware that computes "I + F/16" ?
Maybe the clk-fractional-divider could be made more generic by having
the register update part done in a call-back function?
Regards.
next prev parent reply other threads:[~2016-02-05 16:29 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-05 14:49 Common/typical fractional divider HW API Mason
2016-02-05 15:05 ` Andy Shevchenko
2016-02-05 16:01 ` Mason
2016-02-05 16:12 ` Andy Shevchenko
2016-02-05 16:29 ` Mason [this message]
2016-02-05 16:43 ` Andy Shevchenko
2016-02-07 16:04 ` Mason
2016-02-15 15:35 ` Andy Shevchenko
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