linux-kernel - Re: [PATCH v4 19/24] PM / devfreq: tegra30: Optimize upper consecutive watermark selection

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Date:   Fri, 19 Jul 2019 10:17:31 +0900
From:   Chanwoo Choi <cw00.choi@...sung.com>
To:     Dmitry Osipenko <digetx@...il.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        MyungJoo Ham <myungjoo.ham@...sung.com>,
        Kyungmin Park <kyungmin.park@...sung.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        linux-pm@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 19/24] PM / devfreq: tegra30: Optimize upper
 consecutive watermark selection

On 19. 7. 19. 오전 10:15, Chanwoo Choi wrote:
> On 19. 7. 19. 오전 9:40, Dmitry Osipenko wrote:
>> В Thu, 18 Jul 2019 18:51:02 +0900
>> Chanwoo Choi <cw00.choi@...sung.com> пишет:
>>
>>> On 19. 7. 8. 오전 7:32, Dmitry Osipenko wrote:
>>>> The memory activity counter may get a bit higher than a watermark
>>>> which is selected based on OPP that corresponds to a highest EMC
>>>> rate, in this case watermark is lower than the actual memory
>>>> activity is and thus results in unwanted "upper" interrupts.
>>>>
>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>> ---
>>>>  drivers/devfreq/tegra30-devfreq.c | 13 ++++++++++++-
>>>>  1 file changed, 12 insertions(+), 1 deletion(-)  
>>>
>>> It seems that you can combine patch19 with patch20.
>>
>> No, consecutive and average watermarks are different things that have
>> different purposes. Consecutive are used for boosting, while average
>> are for significant memory bandwidth changes.
>>
>>>>
>>>> diff --git a/drivers/devfreq/tegra30-devfreq.c
>>>> b/drivers/devfreq/tegra30-devfreq.c index
>>>> 8d6bf6e9f1ae..c3cf87231d25 100644 ---
>>>> a/drivers/devfreq/tegra30-devfreq.c +++
>>>> b/drivers/devfreq/tegra30-devfreq.c @@ -363,7 +363,18 @@ static
>>>> void tegra_devfreq_update_wmark(struct tegra_devfreq *tegra,
>>>> tegra_actmon_get_lower_upper(tegra, dev, freq - 1, &lower, &upper); 
>>>>  	delta = do_percent(upper - lower,
>>>> dev->config->boost_up_threshold);
>>>> -	device_writel(dev, lower + delta, ACTMON_DEV_UPPER_WMARK);
> 
> This line was added on patch5 and then this line is removed on this patch.
> It is wrong method to make the patch in the same patchset.
> 
> It is enough to reduce the inefficient add/remove code in the same patchset.

I'm missing some expression. So, I update my comment as following:
It is possible to reduce the inefficient add/remove code in the same patchset
if you combine the patches.

> 
> Have to merge this patch to patch5.
> 
>>>> +
>>>> +	/*
>>>> +	 * The memory events count could go a bit higher than the
>>>> maximum
>>>> +	 * defined by the OPPs, hence make the upper watermark
>>>> infinitely
>>>> +	 * high to avoid unnecessary upper interrupts in that case.
>>>> +	 */
>>>> +	if (freq == tegra->max_freq)
>>>> +		upper = ULONG_MAX;
>>>> +	else
>>>> +		upper = lower + delta;
>>>> +
>>>> +	device_writel(dev, upper, ACTMON_DEV_UPPER_WMARK);
>>>>  
>>>>  	/*
>>>>  	 * Meanwhile the lower mark is based on the average value
>>>>   
>>>
>>>
>>
>>
>>
> 
> 


-- 
Best Regards,
Chanwoo Choi
Samsung Electronics