Re: [PATCH v4 0/3] hwmon: (pmbus/max31785) refactor inter-access delay handling

[Guenter Roeck]

On 3/19/26 16:50, Pradhan, Sanman wrote:
> From: Sanman Pradhan <psanman@xxxxxxxxxxx>
>
> This v4 series addresses the review feedback regarding 32-bit atomicity
> of the inter-access delay timestamp and resolves the email address mismatch
> identified in the v3 submission.
>
> To prevent torn reads/writes of the 64-bit next_access_backoff timestamp
> on 32-bit architectures, this series now includes a prerequisite patch
> adding a spinlock in struct pmbus_data to protect accesses to that field.

Here is the AI feedback, which essentially confirms
that the spinlock is insufficient.

https://sashiko.dev/#/patchset/20260319234945.151487-1-sanman.pradhan%40hpe.com

Also, the error check for i2c_transfer() is incomplete.

Thanks,
Guenter


> Changes in v4:
> - Introduced a new patch (1/3) to protect 64-bit next_access_backoff
>    accesses with a spinlock, avoiding torn reads/writes on 32-bit
>    systems.
> - Updated the export patch (2/3) so pmbus_wait() and pmbus_update_ts()
>    use that protection when accessing next_access_backoff.
> - Standardized all commits and signatures on psanman@xxxxxxxxxxx to
>    resolve the From/SOB mismatch.
>
> Changes in v3:
> - Dropped the u16 -> u8 wrapper type fix (already applied upstream).
> - Fixed a comment style nit in max31785_read_long_data().
> - Added an explicit max31785_wait() before pmbus_do_probe() to ensure
>    proper timing spacing during the handover to the PMBus core.
>
> Changes in v2:
> - Export pmbus_wait() and pmbus_update_ts() from the core.
> - Use core timing helpers in max31785 to replace local usleep_range()
>    boilerplate and private timing state.
>
> Sanman Pradhan (3):
>    hwmon: (pmbus) add spinlock to protect 64-bit timestamp
>    hwmon: (pmbus) export pmbus_wait and pmbus_update_ts
>    hwmon: (pmbus/max31785) use access_delay for PMBus-mediated accesses
>
>   drivers/hwmon/pmbus/max31785.c   | 191 ++++++++++---------------------
>   drivers/hwmon/pmbus/pmbus.h      |   9 ++
>   drivers/hwmon/pmbus/pmbus_core.c |  29 +++--
>   3 files changed, 87 insertions(+), 142 deletions(-)