linux-kernel - Re: [PATCH v3 3/3] counter: 104-quad-8: Utilize helper functions to handle PR, FLAG and PSC

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Message-ID: <ZDVpJb9DyIU+5eJf@fedora>
Date:   Tue, 11 Apr 2023 10:05:25 -0400
From:   William Breathitt Gray <william.gray@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Johannes Berg <johannes.berg@...el.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: [PATCH v3 3/3] counter: 104-quad-8: Utilize helper functions to
 handle PR, FLAG and PSC

On Tue, Apr 11, 2023 at 04:50:03PM +0300, Andy Shevchenko wrote:
> On Mon, Apr 10, 2023 at 10:03:13AM -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.
> 
> ...
> 
> >  	*val = 0;
> 
> Is not needed now as always being initialized by below call.

The regmap_noinc_read() call only reads the number of bytes requested.
Since we request 3 bytes, the upper bytes of the u64 val remain
uninitialized, so that is why we need to set *val = 0. This isn't
immediately clear in the code, so I can add a comment to make it
explicit.

> 
> >  	spin_lock_irqsave(&priv->lock, irqflags);
> >  
> >  	iowrite8(SELECT_RLD | RESET_BP | TRANSFER_CNTR_TO_OL, &chan->control);
> > -
> > -	for (i = 0; i < 3; i++)
> > -		*val |= (unsigned long)ioread8(&chan->data) << (8 * i);
> > +	ioread8_rep(&chan->data, val, 3);
> >  
> >  	spin_unlock_irqrestore(&priv->lock, irqflags);
> 
> ...
> 
> > +	struct channel_reg __iomem *const chan = priv->reg->channel + id;
> 
> Not sure if array representation will look better here and elsewhere.
> 
> 	struct channel_reg __iomem *const chan = &priv->reg->channel[id];

Perhaps so, but all these struct channel_reg lines will go away in the
next patch [0] migrating to the regmap API, so for the sake of stability
of this patch I hesitate to change these lines.

William Breathitt Gray

[0] https://lore.kernel.org/all/20230410141252.143998-1-william.gray@linaro.org/

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