linux-kernel - Re: [PATCH V5 02/18] pinctrl: tegra: Add suspend and resume support

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Date:   Sat, 29 Jun 2019 18:58:43 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Sowjanya Komatineni <skomatineni@...dia.com>,
        thierry.reding@...il.com, jonathanh@...dia.com, tglx@...utronix.de,
        jason@...edaemon.net, marc.zyngier@....com,
        linus.walleij@...aro.org, stefan@...er.ch, mark.rutland@....com
Cc:     pdeschrijver@...dia.com, pgaikwad@...dia.com, sboyd@...nel.org,
        linux-clk@...r.kernel.org, linux-gpio@...r.kernel.org,
        jckuo@...dia.com, josephl@...dia.com, talho@...dia.com,
        linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org,
        mperttunen@...dia.com, spatra@...dia.com, robh+dt@...nel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH V5 02/18] pinctrl: tegra: Add suspend and resume support

29.06.2019 18:46, Dmitry Osipenko пишет:
> 28.06.2019 5:12, Sowjanya Komatineni пишет:
>> This patch adds support for Tegra pinctrl driver suspend and resume.
>>
>> During suspend, context of all pinctrl registers are stored and
>> on resume they are all restored to have all the pinmux and pad
>> configuration for normal operation.
>>
>> Acked-by: Thierry Reding <treding@...dia.com>
>> Signed-off-by: Sowjanya Komatineni <skomatineni@...dia.com>
>> ---
>>  drivers/pinctrl/tegra/pinctrl-tegra.c    | 52 ++++++++++++++++++++++++++++++++
>>  drivers/pinctrl/tegra/pinctrl-tegra.h    |  3 ++
>>  drivers/pinctrl/tegra/pinctrl-tegra210.c |  1 +
>>  3 files changed, 56 insertions(+)
>>
>> diff --git a/drivers/pinctrl/tegra/pinctrl-tegra.c b/drivers/pinctrl/tegra/pinctrl-tegra.c
>> index 34596b246578..e7c0a1011cba 100644
>> --- a/drivers/pinctrl/tegra/pinctrl-tegra.c
>> +++ b/drivers/pinctrl/tegra/pinctrl-tegra.c
>> @@ -621,6 +621,43 @@ static void tegra_pinctrl_clear_parked_bits(struct tegra_pmx *pmx)
>>  	}
>>  }
>>  
>> +static int tegra_pinctrl_suspend(struct device *dev)
>> +{
>> +	struct tegra_pmx *pmx = dev_get_drvdata(dev);
>> +	u32 *backup_regs = pmx->backup_regs;
>> +	u32 *regs;
>> +	unsigned int i, j;
>> +
>> +	for (i = 0; i < pmx->nbanks; i++) {
>> +		regs = pmx->regs[i];
>> +		for (j = 0; j < pmx->reg_bank_size[i] / 4; j++)
>> +			*backup_regs++ = readl(regs++);
>> +	}
>> +
>> +	return pinctrl_force_sleep(pmx->pctl);
>> +}
>> +
>> +static int tegra_pinctrl_resume(struct device *dev)
>> +{
>> +	struct tegra_pmx *pmx = dev_get_drvdata(dev);
>> +	u32 *backup_regs = pmx->backup_regs;
>> +	u32 *regs;
>> +	unsigned int i, j;
>> +
>> +	for (i = 0; i < pmx->nbanks; i++) {
>> +		regs = pmx->regs[i];
>> +		for (j = 0; j < pmx->reg_bank_size[i] / 4; j++)
>> +			writel(*backup_regs++, regs++);
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +const struct dev_pm_ops tegra_pinctrl_pm = {
>> +	.suspend = &tegra_pinctrl_suspend,
>> +	.resume = &tegra_pinctrl_resume
>> +};
> 
> Hm, so this are the generic platform-driver suspend-resume OPS here, which is very
> nice! But.. shouldn't pinctrl be resumed before the CLK driver (which is syscore_ops
> in this version of the series)? .. Given that "clock" function may need to be
> selected for some of the pins.
> 

Oh, also what about GPIO-pinctrl suspend resume ordering .. is it okay that pinctrl
will be resumed after GPIO? Shouldn't a proper pin-muxing be selected at first?

This also looks to me very unsafe in a context of older Tegras which are initializing
the static muxing very early during of the boot, otherwise things won't work well for
the drivers.