linux-kernel - Re: [PATCH v5 3/3] gpio: ws16c48: Migrate to the regmap API

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Date:   Mon, 3 Apr 2023 22:12:44 +0100
From:   Mark Brown <broonie@...nel.org>
To:     William Breathitt Gray <william.gray@...aro.org>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        linux-kernel@...r.kernel.org, linux-gpio@...r.kernel.org,
        techsupport@...systems.com,
        Paul Demetrotion <pdemetrotion@...systems.com>,
        Michael Walle <michael@...le.cc>
Subject: Re: [PATCH v5 3/3] gpio: ws16c48: Migrate to the regmap API

On Sun, Apr 02, 2023 at 10:39:02AM -0400, William Breathitt Gray wrote:
> On Mon, Mar 27, 2023 at 02:26:37PM +0300, Andy Shevchenko wrote:
> > On Sun, Mar 26, 2023 at 12:25:59PM -0400, William Breathitt Gray wrote:

> > > +static const struct regmap_config ws16c48_regmap_config = {
> > > +	.reg_bits = 8,
> > > +	.reg_stride = 1,
> > > +	.val_bits = 8,
> > > +	.io_port = true,
> > > +	.max_register = 0xA,
> > > +	.wr_table = &ws16c48_wr_table,
> > > +	.rd_table = &ws16c48_rd_table,
> > > +	.volatile_table = &ws16c48_volatile_table,
> > > +	.cache_type = REGCACHE_FLAT,
> > > +};

> > Do we need regmap lock?

> We make regmap calls within an interrupt context in this driver so I
> think we need to disable the default regmap mutex locking behavior; I
> believe the current raw_spin_lock locking in this driver is enough to
> protect access.

The above doesn't configure the regmap locking so you'll have a spinlock
by default (MMIO being a fast bus).

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