[PATCH] ARM: aspeed: Disable UCD90160 in the Witherspoon devicetree

[Xo Wang]

On Thu, Mar 23, 2017 at 7:05 PM, Andrew Jeffery <andrew at aj.id.au> wrote:
> Xo: Adding you in case you've seen any issues with Zaius that may
> benefit from a similar work-around in the short term.
>

Thanks for the copy. I haven't seen the unsupported command errors
from the UCD90160 on Zaius. I suspect it's because we perform less
i2c-get/-set on our UCD, since it is already programmed to treat the
UCD rails' control pins as output GPIOs.

Do those errors you see always come after a UCD9000 driver bind operation?

> The associated userspace changes for Witherspoon are here:
>
> https://gerrit.openbmc-project.xyz/#/q/topic:unbound-ucd+status:open
>
> Andrew
>
> On Fri, 2017-03-24 at 11:43 +1030, Andrew Jeffery wrote:
>> This is a work-around for [1]. Binding the UCD9000 driver to the device (and
>> possibly the sequence of unbinding, poking the UCD90160 via i2cset, then
>> re-binding the UCD9000 driver) appears to have some negative effects.
>> Instrumenting the transactions with reads of the PMBus status tree lead to
>> the following observations under "normal" operation.
>>
>> [1] https://github.com/openbmc/openbmc/issues/832
>>
>> UCD9000/PMBus core sending unsupported commands:
>>
>>          Jan 24 06:42:50 witherspoon kernel: ucd9000 11-0064: Device ID UCD90160|2.3.4.0000|110603
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: Status byte indicates error: 0x3
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: Unknown error
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: CML status: 0x80
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: Invalid Or Unsupported Command Received
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: Transfer failed: -5, status was 0x3
>>          Jan 24 06:42:50 witherspoon kernel: i2c i2c-11: Aborting retries after 1 attempts, returning error -5
>>
>> Reading the status bytes off the UCD90160 gives -EBADMSG:
>>
>>          Jan 24 06:43:21 witherspoon kernel: i2c i2c-11: Error reading PMBUS_STATUS_BYTE: -74
>>          ...
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Error reading PMBUS_STATUS_CML: -74
>>
>> "Other comms fault" errors:
>>
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Status byte indicates error: 0x3
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Unknown error
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: CML status: 0x82
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Other comms fault
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Invalid Or Unsupported Command Received
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Transfer failed: -5, status was 0x3
>>          Jan 24 06:43:56 witherspoon kernel: i2c i2c-11: Retrying transfer (attempt 1)
>>          Jan 24 06:43:57 witherspoon kernel: i2c i2c-11: Status byte indicates error: 0x3
>>          Jan 24 06:43:57 witherspoon kernel: i2c i2c-11: Unknown error
>>          Jan 24 06:43:57 witherspoon kernel: i2c i2c-11: CML status: 0x2
>>          Jan 24 06:43:57 witherspoon kernel: i2c i2c-11: Other comms fault
>>          Jan 24 06:43:57 witherspoon kernel: i2c i2c-11: Retrying transfer (attempt 1)
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: Status byte indicates error: 0x3
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: Unknown error
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: CML status: 0x80
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: Invalid Or Unsupported Command Received
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: Transfer failed: -5, status was 0x3
>>          Jan 24 06:43:59 witherspoon kernel: i2c i2c-11: Aborting retries after 1 attempts, returning error -5
>>
>> Reduce our problems by communicating with the UCD90160 as little as possible.
>> With the associated userspace change, the only communication will be applying
>> the VCS work-around.
>>
>> > Signed-off-by: Andrew Jeffery <andrew at aj.id.au>
>> ---
>>  arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts b/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts
>> index 4d26d4702a34..69d5897dbfde 100644
>> --- a/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts
>> +++ b/arch/arm/boot/dts/aspeed-bmc-opp-witherspoon.dts
>> @@ -253,6 +253,7 @@
>> >     };
>>
>> >     ucd90160 at 64 {
>> > +           status = "disabled";
>> >             compatible = "ti,ucd90160";
>> >             reg = <0x64>;
>> >     };

cheers
xo