[PATCH linux dev-4.10 0/3] pmbus: Misc work-arounds for the PAGE command

[Andrew Jeffery]

On Thu, 2017-10-26 at 16:49 +1030, Andrew Jeffery wrote:
> Hello,
> 
> Occasionally the MAX31785 NACKs setting the page on the device. The consequence
> is the PMBus core either thinks some functionality is unsupported by the device
> or it inspects features on the wrong page after swallowing the error.
> 
> The most obvious side-effect is that some hwmon attributes are not created when
> they should be, often causing issues for fan monitoring and control in
> userspace, preventing the host from booting.
> 
> The series introduces a one-shot retry in the PMBus core for the PAGE command.
> This is generally terrible, but the alternatives seem worse. Also this is not
> yet appropriate to upstream as I haven't succeeded in getting the MAX31785
> driver applied there. As a result this dirty secret can live in the OpenBMC
> tree until we properly understand the problem.
> 
> The first couple of patches help avoid setting PAGE to values that never make
> sense. Again this involves a questionable change to the PMBus core, but I think
> we can live with it.
> 
> Some brief testing of the series indicates that all one-shot attempts succeed
> in the face of a previous failure, much like the FAN_CONFIG_* issues.
> 
> Let me know what you think!
> 
> Andrew Jeffery (3):
>   hwmon: pmbus: core: Add virtual page config bit
>   hwmon: pmbus: max31785: Mark virtual pages as virtual
>   hwmon: pmbus: core: One-shot retries for failure to set page

I've applied these to dev-4.10 with Matt Spinler's Reviewed-by tags.

Cheers,

Andrew

> 
>  drivers/hwmon/pmbus/max31785.c   |  1 +
>  drivers/hwmon/pmbus/pmbus.h      |  2 ++
>  drivers/hwmon/pmbus/pmbus_core.c | 23 +++++++++++++++++++----
>  3 files changed, 22 insertions(+), 4 deletions(-)
> 
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