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

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Date:   Fri, 19 Jul 2019 03:40:25 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Chanwoo Choi <cw00.choi@...sung.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

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);
> > +
> > +	/*
> > +	 * 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
> >   
> 
>