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

From: Dmitry Osipenko <digetx@gmail.com>
To: Viresh Kumar <viresh.kumar@linaro.org>
Cc: Ulf Hansson <ulf.hansson@linaro.org>,
	Michael Turquette <mturquette@baylibre.com>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	Thierry Reding <thierry.reding@gmail.com>,
	linux-clk@vger.kernel.org, devel@driverdev.osuosl.org,
	Kevin Hilman <khilman@kernel.org>,
	Nicolas Chauvet <kwizart@gmail.com>,
	Viresh Kumar <vireshk@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Jonathan Hunter <jonathanh@nvidia.com>,
	linux-media@vger.kernel.org, devicetree@vger.kernel.org,
	Rob Herring <robh+dt@kernel.org>,
	linux-tegra@vger.kernel.org,
	Mauro Carvalho Chehab <mchehab@kernel.org>,
	Stephen Boyd <sboyd@kernel.org>,
	Peter De Schrijver <pdeschrijver@nvidia.com>,
	"Rafael J. Wysocki" <rjw@rjwysocki.net>,
	Liam Girdwood <lgirdwood@gmail.com>,
	Mark Brown <broonie@kernel.org>, Peter Geis <pgwipeout@gmail.com>
Subject: Re: [PATCH v2 28/48] soc/tegra: Introduce core power domain driver
Date: Tue, 22 Dec 2020 22:21:03 +0300	[thread overview]
Message-ID: <c130f78d-3d97-9b26-be77-951fee0d8680@gmail.com> (raw)
In-Reply-To: <20201222064029.duuzcsj53rt7xzvt@vireshk-i7>

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.
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