linux-kernel - Re: [PATCH v1 17/30] mmc: sdhci-tegra: Support OPP and core voltage scaling

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Date:   Mon, 9 Nov 2020 08:19:32 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Frank Lee <tiny.windzz@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Alan Stern <stern@...land.harvard.edu>,
        Peter Chen <Peter.Chen@....com>,
        Mark Brown <broonie@...nel.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Lee Jones <lee.jones@...aro.org>,
        Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Peter Geis <pgwipeout@...il.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        driver-dev <devel@...verdev.osuosl.org>,
        linux-pwm@...r.kernel.org,
        linux-samsung-soc <linux-samsung-soc@...r.kernel.org>,
        DTML <devicetree@...r.kernel.org>, linux-usb@...r.kernel.org,
        "open list:SECURE DIGITAL HO..." <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        linux-tegra@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: [PATCH v1 17/30] mmc: sdhci-tegra: Support OPP and core voltage
 scaling

09.11.2020 08:10, Viresh Kumar пишет:
> On 09-11-20, 08:08, Dmitry Osipenko wrote:
>> 09.11.2020 08:00, Viresh Kumar пишет:
>>> On 06-11-20, 21:41, Frank Lee wrote:
>>>> On Fri, Nov 6, 2020 at 9:18 PM Dmitry Osipenko <digetx@...il.com> wrote:
>>>>>
>>>>> 06.11.2020 09:15, Viresh Kumar пишет:
>>>>>> Setting regulators for count as 0 doesn't sound good to me.
>>>>>>
>>>>>> But, I understand that you don't want to have that if (have_regulator)
>>>>>> check, and it is a fair request. What I will instead do is, allow all
>>>>>> dev_pm_opp_put*() API to start accepting a NULL pointer for the OPP
>>>>>> table and fail silently. And so you won't be required to have this
>>>>>> unwanted check. But you will be required to save the pointer returned
>>>>>> back by dev_pm_opp_set_regulators(), which is the right thing to do
>>>>>> anyways.
>>>>>
>>>>> Perhaps even a better variant could be to add a devm versions of the OPP
>>>>> API functions, then drivers won't need to care about storing the
>>>>> opp_table pointer if it's unused by drivers.
>>>>
>>>> I think so. The consumer may not be so concerned about the status of
>>>> these OPP tables.
>>>> If the driver needs to manage the release, it needs to add a pointer
>>>> to their driver global structure.
>>>>
>>>> Maybe it's worth having these devm interfaces for opp.
>>>
>>> Sure if there are enough users of this, I am all for it. I was fine
>>> with the patches you sent, just that there were not a lot of users of
>>> it and so I pushed them back. If we find that we have more users of it
>>> now, we can surely get that back.
>>>
>>
>> There was already attempt to add the devm? Could you please give me a
>> link to the patches?
>>
>> I already prepared a patch which adds the devm helpers. It helps to keep
>> code cleaner and readable.
> 
> https://lore.kernel.org/lkml/20201012135517.19468-1-frank@allwinnertech.com/
> 

Thanks, I made it in a different way by simply adding helpers to the
pm_opp.h which use devm_add_action_or_reset(). This doesn't require to
add new kernel symbols.

static inline int devm_pm_opp_of_add_table(struct device *dev)
{
	int err;

	err = dev_pm_opp_of_add_table(dev);
	if (err)
		return err;

	err = devm_add_action_or_reset(dev, (void*)dev_pm_opp_remove_table,
				       dev);
	if (err)
		return err;

	return 0;
}