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

[Andrew Jeffery]

Xo: Adding you in case you've seen any issues with Zaius that may
benefit from a similar work-around in the short term.

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>;
> >  	};
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