Re: [PATCH v2] hwmon: (pmbus/mp2975) Get vout fault limits dynamically

[sashiko-bot@kernel.org]

> The over- and under-voltage fault limits of the tracking mode are
> relative to the voltage reference, which follows the VID/AVS requests
> issued to the device and therefore changes at runtime.
> 
> The driver reads the voltage reference once during probe and derives the
> limits from that snapshot, which the PMBus core caches in addition. As a
> result in2_crit and in2_lcrit reflect the operating point at probe, rather
> than the thresholds the device enforces. On systems where the device
> supplies the CPU core voltage, in2_crit was reported anywhere between
> 1.15V and 1.70V across identical systems, causing false over-voltage
> reports once the CPU voltage exceeded the value latched at probe.
> 
> Read the voltage reference and the over-voltage offset selector whenever
> a limit is requested, and mark both limits with pmbus_set_update(), so
> that the core does not cache them. The voltage reference is available on
> page 3 only. Let the core change the page, so that the page it caches
> matches the device, except for a single rail configuration, for which the
> core does not issue PAGE commands, and the page is changed directly.
> 
> With the selector read at runtime, a device configured with an
> unsupported selector no longer fails to probe. The OVP1 threshold, which
> does not depend on the selector, is reported for it instead, with a
> warning.
> 
> Clamp the under-voltage limit to zero, since the offset can exceed a low
> voltage reference, while a negative value would be reported as a read
> error.
> 
> Fixes: 2c6fcbb21149 ("hwmon: (pmbus) Add support for MPS Multi-phase mp2975 controller")
> Signed-off-by: Felix Radensky <fradensky@nvidia.com>

Sashiko has reviewed this patch and found no issues.

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