linux-kernel - Re: [PATCH v6 3/7] mfd: Add MFD driver for ATC260x PMICs

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Message-ID: <20210125184715.GA1061394@BV030612LT>
Date:   Mon, 25 Jan 2021 20:47:15 +0200
From:   Cristian Ciocaltea <cristian.ciocaltea@...il.com>
To:     Lee Jones <lee.jones@...aro.org>
Cc:     Mark Brown <broonie@...nel.org>, Rob Herring <robh+dt@...nel.org>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Liam Girdwood <lgirdwood@...il.com>,
        Andreas Färber <afaerber@...e.de>,
        Linus Walleij <linus.walleij@...aro.org>,
        linux-actions@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-pm@...r.kernel.org
Subject: Re: [PATCH v6 3/7] mfd: Add MFD driver for ATC260x PMICs

Hi Lee,

On Mon, Jan 25, 2021 at 02:25:58PM +0000, Lee Jones wrote:
> On Wed, 20 Jan 2021, Cristian Ciocaltea wrote:
> 
> > Add initial support for the Actions Semi ATC260x PMICs which integrates
> > Audio Codec, Power management, Clock generation and GPIO controller
> > blocks.
> > 
> > For the moment this driver only supports Regulator, Poweroff and Onkey
> > functionalities for the ATC2603C and ATC2609A chip variants.
 
[...]

> > +static void regmap_lock_mutex(void *__mutex)
> > +{
> > +	struct mutex *mutex = __mutex;
> > +
> > +	/*
> > +	 * Using regmap within an atomic context (e.g. accessing a PMIC when
> > +	 * powering system down) is normally allowed only if the regmap type
> > +	 * is MMIO and the regcache type is either REGCACHE_NONE or
> > +	 * REGCACHE_FLAT. For slow buses like I2C and SPI, the regmap is
> > +	 * internally protected by a mutex which is acquired non-atomically.
> > +	 *
> > +	 * Let's improve this by using a customized locking scheme inspired
> > +	 * from I2C atomic transfer. See i2c_in_atomic_xfer_mode() for a
> > +	 * starting point.
> > +	 */
> > +	if (system_state > SYSTEM_RUNNING && irqs_disabled())
> > +		mutex_trylock(mutex);
> > +	else
> > +		mutex_lock(mutex);
> > +}
> 
> Would this be useful to anyone else?

If you refer to the locking scheme, it is currently required by the
power-off driver to handle atomic contexts.

> For my own reference (apply this as-is to your sign-off block):

Please note the patches "[4/7] regulator: ..." and "[5/7] power: ..."
have been already picked up by Mark and Sebastian, respectively, while
Dmitry suggested to merge "[6/7] input: ..." through MFD.

>   Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> 
> -- 
> Lee Jones [李琼斯]
> Senior Technical Lead - Developer Services
> Linaro.org │ Open source software for Arm SoCs
> Follow Linaro: Facebook | Twitter | Blog

Thanks,
Cristi