linux-kernel - Re: [Patch] driver: cpufreq: use refclk delta based loop instead of udelay

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Message-ID: <f0059dd9-e258-80e9-bc4d-c8ee0c72a754@nvidia.com>
Date:   Fri, 1 Sep 2023 22:19:46 +0530
From:   Sumit Gupta <sumitg@...dia.com>
To:     Jon Hunter <jonathanh@...dia.com>, <rafael@...nel.org>,
        <viresh.kumar@...aro.org>, <linux-pm@...r.kernel.org>,
        <linux-tegra@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:     <treding@...dia.com>, <bbasu@...dia.com>
Subject: Re: [Patch] driver: cpufreq: use refclk delta based loop instead of
 udelay



On 01/09/23 21:28, Jon Hunter wrote:
> 
> 
> On 01/09/2023 16:20, Sumit Gupta wrote:
>> Use reference clock count based loop instead of "udelay()" for
>> sampling of counters to improve the accuracy of re-generated CPU
>> frequency. "udelay()" internally calls "WFE" which stops the
>> counters and results in bigger delta between the last set freq
>> and the re-generated value from counters. The counter sampling
>> window used in loop is the minimum number of reference clock
>> cycles which is known to give a stable value of CPU frequency.
>> The change also helps to reduce the sampling window from "500us"
>> to "<50us".
>>
>> Suggested-by: Antti Miettinen <amiettinen@...dia.com>
>> Signed-off-by: Sumit Gupta <sumitg@...dia.com>
> 
> 
> Please can you correct the subject and drop the 'driver:'.
> 
> Jon
> 

Corrected subject and added another patch in v2 at [1].

[1] https://lore.kernel.org/lkml/20230901164113.29139-1-sumitg@nvidia.com/

Thank you,
Sumit Gupta