linux-kernel - Re: [PATCH v2 28/48] soc/tegra: Introduce core power domain driver

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Message-ID: <c130f78d-3d97-9b26-be77-951fee0d8680@gmail.com>
Date:   Tue, 22 Dec 2020 22:21:03 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Kevin Hilman <khilman@...nel.org>,
        Peter De Schrijver <pdeschrijver@...dia.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Stephen Boyd <sboyd@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linux-media@...r.kernel.org, linux-tegra@...r.kernel.org,
        linux-clk@...r.kernel.org
Subject: Re: [PATCH v2 28/48] soc/tegra: Introduce core power domain driver

22.12.2020 09:40, Viresh Kumar пишет:
> On 17-12-20, 21:06, Dmitry Osipenko wrote:
>> +++ b/drivers/soc/tegra/core-power-domain.c
>> @@ -0,0 +1,125 @@
>> +// SPDX-License-Identifier: GPL-2.0+
>> +/*
>> + * NVIDIA Tegra SoC Core Power Domain Driver
>> + */
>> +
>> +#include <linux/of_device.h>
>> +#include <linux/platform_device.h>
>> +#include <linux/pm_domain.h>
>> +#include <linux/pm_opp.h>
>> +#include <linux/slab.h>
>> +
>> +#include <soc/tegra/common.h>
>> +
>> +static struct lock_class_key tegra_core_domain_lock_class;
>> +static bool tegra_core_domain_state_synced;
>> +
>> +static int tegra_genpd_set_performance_state(struct generic_pm_domain *genpd,
>> +					     unsigned int level)
>> +{
>> +	struct dev_pm_opp *opp;
>> +	int err;
>> +
>> +	opp = dev_pm_opp_find_level_ceil(&genpd->dev, &level);
> 
> We don't need ceil or floor versions for level, but rather _exact() version. Or
> maybe just call it dev_pm_opp_find_level().

The _exact() version won't find OPP for level=0 if levels don't start
with 0.

>> +	if (IS_ERR(opp)) {
>> +		dev_err(&genpd->dev, "failed to find OPP for level %u: %pe\n",
>> +			level, opp);
>> +		return PTR_ERR(opp);
>> +	}
>> +
>> +	err = dev_pm_opp_set_voltage(&genpd->dev, opp);
> 
> IIUC, you implemented this callback because you want to use the voltage triplet
> present in the OPP table ?
> 
> And so you are setting the regulator ("power") later in this patch ?

yes

> I am not in favor of implementing this routine, as it just adds a wrapper above
> the regulator API. What you should be doing rather is get the regulator by
> yourself here (instead of depending on the OPP core). And then you can do
> dev_pm_opp_get_voltage() here and set the voltage yourself. You may want to
> implement a version supporting triplet here though for the same.
> 
> And you won't require the sync version of the API as well then.
> 

That's what I initially did for this driver. I don't mind to revert back
to the initial variant in v3, it appeared to me that it will be nicer
and cleaner to have OPP API managing everything here.