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

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Date:   Fri, 19 Jul 2019 10:15:06 +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 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.

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