linux-kernel - Re: [PATCH v7 5/6] spi: cs42l43: Add SPI controller support

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Message-ID: <20240119114917.GB16899@ediswmail.ad.cirrus.com>
Date: Fri, 19 Jan 2024 11:49:17 +0000
From: Charles Keepax <ckeepax@...nsource.cirrus.com>
To: <andy.shevchenko@...il.com>
CC: <broonie@...nel.org>, <lee@...nel.org>, <robh+dt@...nel.org>,
        <krzysztof.kozlowski+dt@...aro.org>, <conor+dt@...nel.org>,
        <linus.walleij@...aro.org>, <vkoul@...nel.org>, <lgirdwood@...il.com>,
        <yung-chuan.liao@...ux.intel.com>, <sanyog.r.kale@...el.com>,
        <pierre-louis.bossart@...ux.intel.com>, <alsa-devel@...a-project.org>,
        <patches@...nsource.cirrus.com>, <devicetree@...r.kernel.org>,
        <linux-gpio@...r.kernel.org>, <linux-spi@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v7 5/6] spi: cs42l43: Add SPI controller support

On Thu, Jan 18, 2024 at 07:06:13PM +0200, andy.shevchenko@...il.com wrote:
> Fri, Aug 04, 2023 at 11:46:01AM +0100, Charles Keepax kirjoitti:
> > +		while (buf < block) {
> > +			const u8 *word = min(buf + sizeof(u32), block);
> > +			int pad = (buf + sizeof(u32)) - word;
> > +
> > +			while (buf < word) {
> > +				val >>= BITS_PER_BYTE;
> > +				val |= FIELD_PREP(GENMASK(31, 24), *buf);
> > +
> > +				buf++;
> > +			}
> 
> Is this a reinvented way of get_unaligned_*() APIs?
> 
> > +			val >>= pad * BITS_PER_BYTE;
> > +
> > +			regmap_write(regmap, CS42L43_TX_DATA, val);
> > +		}
> 
> ...
> 
> > +			while (buf < word) {
> > +				*buf = FIELD_GET(GENMASK(7, 0), val);
> > +
> > +				val >>= BITS_PER_BYTE;
> > +				buf++;
> > +			}
> 
> put_unaligned_*() ?
> 

Alas as it has been a while I have forgetten the exact context
here and this one will take a little more time. I will try to
find some spare time to work out if that would actual do the same
thing, I have a vague feeling there was something here.

> ...
> 
> > +	if (is_of_node(fwnode))
> > +		fwnode = fwnode_get_named_child_node(fwnode, "spi");
> 
> You can actually drop these is_of_node() tests and use another variable. In
> ACPI there can't be child node in small letters.
> 

is_of_node feels pretty clear what the intent is, rather than
relying on nodes not existing etc.

> But main problem here (and in another driver where the similar is used) that
> you bumped reference count for fwnode. I haven't seen where you drop it back.
> Have you tested rmmod/modprobe in a loop?
> 

Yeah it should drop the reference will add that.

> > +	devm_pm_runtime_enable(priv->dev);
> 
> No error check? Why?

Happy to add one.

> > +	ret = devm_spi_register_controller(priv->dev, priv->ctlr);
> > +	if (ret) {
> > +		pm_runtime_disable(priv->dev);
> 
> Ah! Are you sure you properly simulated faults when testing this code?

This one has already been fixed.

Thanks,
Charles