linux-kernel - Re: [PATCH 4/4] counter: 104-quad-8: Utilize helper functions to handle PR, FLAG and PSC

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Message-ID: <ZBiBgI5mVHAg/59Y@fedora>
Date:   Mon, 20 Mar 2023 11:53:36 -0400
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-iio@...r.kernel.org, Johannes Berg <johannes.berg@...el.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] counter: 104-quad-8: Utilize helper functions to
 handle PR, FLAG and PSC

On Mon, Mar 20, 2023 at 05:36:17PM +0200, Andy Shevchenko wrote:
> On Mon, Mar 20, 2023 at 11:31:07AM -0400, William Breathitt Gray wrote:
> > On Mon, Mar 20, 2023 at 02:28:31PM +0200, Andy Shevchenko wrote:
> > > On Sat, Mar 18, 2023 at 10:59:51AM -0400, William Breathitt Gray wrote:
> > > > The Preset Register (PR), Flag Register (FLAG), and Filter Clock
> > > > Prescaler (PSC) have common usage patterns. Wrap up such usage into
> > > > dedicated functions to improve code clarity.
> 
> ...
> 
> > > > +static void quad8_preset_register_set(struct quad8 *const priv, const size_t id,
> > > > +				      const unsigned long preset)
> > > > +{
> > > > +	struct channel_reg __iomem *const chan = priv->reg->channel + id;
> > > > +	int i;
> > > > +
> > > > +	/* Reset Byte Pointer */
> > > > +	iowrite8(SELECT_RLD | RESET_BP, &chan->control);
> > > > +
> > > > +	/* Set Preset Register */
> > > > +	for (i = 0; i < 3; i++)
> > > > +		iowrite8(preset >> (8 * i), &chan->data);
> > > > +}
> > > 
> > > May we add generic __iowrite8_copy() / __ioread8_copy() instead?
> > > 
> > > It seems that even current __ioread32_copy() and __iowrite32_copy() has to
> > > be amended to support IO.
> 
> > Sure, I would use __iowrite8_copy() / __ioread8_copy() for these
> > situations if it were available.
> 
> If needed, you may always introduce ones.
> 
> > Is something equivalent available for the regmap API? I'm planning to
> > migrate this driver to the regmap API soon after this patch series is
> > merged, so the *_copy() calls would need to migrated as well.
> 
> Yes. It's regmap bulk operations.
> 
> -- 
> With Best Regards,
> Andy Shevchenko

After reading through the implementation for these functions I realized
they are actually doing something different than what's happening here.
The 104-QUAD-8 device exposes the 24-bit register by consecutive 8-bit
I/O operations on the same address; however, the iomap_copy and regmap
bulk functions operate on different addresses.

I'm not sure if there really is a way to make the 104-QUAD-8 operation
more generic for other drivers because it configures the current byte
pointer through a separate register from the data register (all of this
feel rather device specific), so I suspect keeping this function local
to 104-quad-8 is best for now.

William Breathitt Gray

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