Re: [PATCH v2 1/4] dt-bindings: power: reset: add PSCRR NVMEM recorder binding

[Faruque Ansari <faruque.ansari@oss.qualcomm.com>]

Hi Krzysztof,

On 27-Aug-26 3:15 PM, Krzysztof Kozlowski wrote:
> On Wed, Aug 19, 2026 at 10:50:43PM +0530, Faruque Ansari wrote:
>> Add binding for the PSCRR NVMEM recorder. Records the power state
>> change reason into a small NVMEM cell, such as a PMIC SDAM byte or
>> RTC scratch register — so the cause survives a power cycle and can be
>> read back on the next boot.
> 
> A nit, subject: drop second/last, redundant "binding". The
> "dt-bindings" prefix is already stating that these are bindings.
> See also:
> https://elixir.bootlin.com/linux/v7.1-rc7/source/Documentation/devicetree/bindings/submitting-patches.rst#L23
> 
Thanks for the review.
I'll fix this in V3.

>> Signed-off-by: Faruque Ansari <faruque.ansari@oss.qualcomm.com>
>> ---
>>   .../bindings/power/reset/pscrr-nvmem.yaml          | 59 ++++++++++++++++++++++
>>   MAINTAINERS                                        |  1 +
>>   2 files changed, 60 insertions(+)
>>
>> diff --git a/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
>> new file mode 100644
>> index 000000000000..5334c923d644
>> --- /dev/null
>> +++ b/Documentation/devicetree/bindings/power/reset/pscrr-nvmem.yaml
>> @@ -0,0 +1,59 @@
>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>> +%YAML 1.2
>> +---
>> +$id: http://devicetree.org/schemas/power/reset/pscrr-nvmem.yaml#
>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
>> +
>> +title: NVMEM Power State Change Reason recorder
>> +
>> +maintainers:
>> +  - Faruque Ansari <faruque.ansari@oss.qualcomm.com>
>> +  - Oleksij Rempel <o.rempel@pengutronix.de>
>> +
>> +description:
>> +  An NVMEM-backed recorder for Power State Change Reasons (PSCRR). Persists
>> +  the reboot or shutdown cause into a small NVMEM cell, such as an RTC
>> +  scratch register, a PMIC SDAM (Scratch Data Access Memory) byte, or an
>> +  EEPROM — so the reason survives a power cycle and can be read back on the
>> +  next boot. The cell is referenced via the standard nvmem-cells consumer
>> +  binding.
> 
> I do not see how this should be a separate device. This should be rather part
> of PSCRR, reboot handler or just the nvmem. Otherwise it is just device
> node for instantiating driver.

There's already precedent in-tree for exactly this shape of 
binding: 
Documentation/devicetree/bindings/power/reset/nvmem-reboot-mode.yaml 
defines a standalone "nvmem-reboot-mode" compatible whose sole 
purpose is to bind an nvmem-cell and instantiate a driver that 
writes a reboot-mode value into it before reset, for the 
bootloader to read.

pscrr-nvmem follows the same pattern: instead of a reboot-mode 
value for the bootloader, it records the PSCRR reason into an 
NVMEM cell before reset and reads it back on the next boot for 
PSCRR to report. Like nvmem-reboot-mode, it works with any NVMEM 
backend (RTC scratch register, PMIC SDAM, EEPROM, etc.).

It doesn't fit cleanly into PSCRR core (hardware-agnostic, no 
NVMEM dependency today) or a specific reset handler (it only 
records the reason, it doesn't initiate the reset).


Thanks,
Faruque Ansari