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

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Message-ID: <eb9ef21a-c0b4-4c8d-b1b1-6c76f45c53aa@mleia.com>
Date: Fri, 2 Jan 2026 14:36:07 +0200
From: Vladimir Zapolskiy <vz@...ia.com>
To: Krzysztof Kozlowski <krzk@...nel.org>, Arnd Bergmann <arnd@...db.de>
Cc: Piotr Wojtaszczyk <piotr.wojtaszczyk@...esys.com>,
 linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] soc: nxp: Add a simple NXP LPC32xx socinfo driver

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@...ia.com>
>> ---
>>   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