Re: [PATCH 2/2] soc: nxp: Add a simple NXP LPC32xx socinfo driver

[Vladimir Zapolskiy]

On 1/2/26 11:58, Krzysztof Kozlowski wrote:
> On 02/01/2026 00:56, Vladimir Zapolskiy wrote:
> > Add NXP LPC32xx specific driver to get unique SoC ID from System Control
> > Block registers and export it to userspace.
> >
> > Signed-off-by: Vladimir Zapolskiy <vz@xxxxxxxxx>
> > ---
> >   drivers/soc/Kconfig           |   1 +
> >   drivers/soc/Makefile          |   1 +
> >   drivers/soc/nxp/Kconfig       |  16 +++++
> >   drivers/soc/nxp/Makefile      |   2 +
> >   drivers/soc/nxp/lpc32xx-soc.c | 114 ++++++++++++++++++++++++++++++++++
> >   5 files changed, 134 insertions(+)
> >   create mode 100644 drivers/soc/nxp/Kconfig
> >   create mode 100644 drivers/soc/nxp/Makefile
> >   create mode 100644 drivers/soc/nxp/lpc32xx-soc.c
> >
> > diff --git a/drivers/soc/Kconfig b/drivers/soc/Kconfig
> > index a2d65adffb80..c21b0d2f58fc 100644
> > --- a/drivers/soc/Kconfig
> > +++ b/drivers/soc/Kconfig
> > @@ -18,6 +18,7 @@ source "drivers/soc/loongson/Kconfig"
> >   source "drivers/soc/mediatek/Kconfig"
> >   source "drivers/soc/microchip/Kconfig"
> >   source "drivers/soc/nuvoton/Kconfig"
> > +source "drivers/soc/nxp/Kconfig"
> >   source "drivers/soc/pxa/Kconfig"
> >   source "drivers/soc/qcom/Kconfig"
> >   source "drivers/soc/renesas/Kconfig"
> > diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
> > index 47a3925ff84c..a04c21a8a5a4 100644
> > --- a/drivers/soc/Makefile
> > +++ b/drivers/soc/Makefile
> > @@ -24,6 +24,7 @@ obj-y				+= loongson/
> >   obj-y				+= mediatek/
> >   obj-y				+= microchip/
> >   obj-y				+= nuvoton/
> > +obj-y				+= nxp/
> >   obj-y				+= pxa/
> >   obj-y				+= qcom/
> >   obj-y				+= renesas/
>
> Missing maintainers entry.
>
>
> > +
> > +static int lpc32xx_soc_probe(struct platform_device *pdev)
> > +{
> > +	struct soc_device_attribute *soc_dev_attr;
> > +	struct device *dev = &pdev->dev;
> > +	struct soc_device *soc_dev;
> > +	struct regmap *scb;
> > +	u32 serial_id[4];
> > +	int ret;
> > +
> > +	soc_dev_attr = devm_kzalloc(dev, sizeof(*soc_dev_attr), GFP_KERNEL);
> > +	if (!soc_dev_attr)
> > +		return -ENOMEM;
> > +
> > +	soc_dev_attr->family = "NXP LPC32xx";
> > +
> > +	ret = of_property_read_string(of_root, "model", &soc_dev_attr->machine);
> > +	if (ret)
> > +		return ret;
> > +
> > +	scb = syscon_regmap_lookup_by_compatible("nxp,lpc3220-scb");
>
> This is undocumented ABI.

What is the expected level of documentation for syscon?

The mfd/syscon.yaml states:

  System controller node represents a register region containing a set
  of miscellaneous registers. The registers are not cohesive enough to
  represent as any specific type of device.

This particular SCB has been documented, the review is pending.

> Anyway, you should look up devices via phandles.

I may miss the context, was syscon_regmap_lookup_by_compatible() deprecated?

Most of drivers/soc uses syscon_regmap_lookup_by_compatible() variant over
syscon_regmap_lookup_by_phandle(), and overall

% git grep syscon_regmap_lookup_by_compatible v6.19-rc1 | wc -l
105

--
Best wishes,
Vladimir