RE: phosphor-isolation

["Milton Miller II" <miltonm@us.ibm.com>]

Around 09/20/2019 01:16PM in some timezone James Feist wrote:>On 9/20/19 9:20 AM, Milton Miller II wrote:
>> On September 20, 2019, around 10:56AM in some timezone, James Feist wrote:
>>> On 9/19/19 8:47 PM, Andrew Jeffery wrote:
>>>> On Fri, 20 Sep 2019, at 03:03, James Feist wrote:
>>>>> I enabled phosphor-isolation on my system and noticed that kcs
>>>>> >no
>>>>> longer
>>>>> worked afterwards. Commenting out this section:
>>>>>
>>>>>
>> 
>>>>>
>>>>> +	/* iLPC2AHB */
>>>>> +	val = readl(AST_SCU_BASE + AST_SCU_HW_STRAP1);
>>>>> +	val |= SCU_HW_STRAP_LPC_DEC_SUPER_IO;
>>>>> +	writel(val, AST_SCU_BASE + AST_SCU_HW_STRAP1);
>>>>>
>>>>>
>>>>> Seems to make KCS work again.
>> 
>> That configuration is disabling superio decoding, which means the
>host
>> will no longer be able to configure the superio hardware on the LPC
>bus.
>> 
>>>>
>>>> That is an unexpected result. Have you asked ASPEED about it?
>>>> I've
>>>> added
>>>> Ryan to Cc. I must admit I didn't test the patch with systems
>>>> that
>>>> use KCS
>>>> because OpenPOWER exclusively uses BT for IPMI (though we're
>>>> starting
>>>> to exploit the KCS interfaces for an LPC MCTP binding).
>>>>
>>>> Having said that, the systems that we're testing our LPC MCTP
>>>> binding on
>>>> would have this patch applied, so presumably we're not seeing the
>>>> same
>>>> effect there. They're 2500-based systems, is that what you're
>>>> testing with?
>>>
>>> Yes I am.
>>>
>> 
>> As an outside observer without hardware, can you check:
>> 
>> (1) Did you check from the OS or just from a BIOS inventory?
>
>Attempting to send ipmi commands from uefi/linux stopped working.
>Linux 
>driver on host reported issues communicating to bmc.
>
>> 
>> (2) Is there code to enable the KCS peripheral from the bmc
>
>There is a driver and kcsbridged.

Those are probably drivers to respond to data sent 
over the bridge.  I was looking more to "is the KCS 
peripherial enabled on the LPC bus at the expected 
address?"

If you add mem.devmem=y [1] to the kernel command line 
you can use devmem at runtime to reverse that bit via 
/dev/mem and then use an sio configuration tool from 
the host to query how its configured.  


There is probably another way to do it from the bmc 
side but I don't know where to start looking (probably 
somewhere in the lpc space).


[1] https://github.com/openbmc/linux/blob/707b68f43a8cc94fe5dcc4e35dad778828ca9cc9/drivers/char/mem.c#L921

>> 
>> (3) Will the host try to use the KCS even though it can
>>      not find the superio to choose the port and interrupt?
>
>Yes.
>
>> 
>> 
>> 
>> 
>> 
>>>>>
>>>>> Do we need this part set? If so, should we
>>>>> create a phosphor-isolation-kcs and phosphor-isolation-bt?
>>>>
>>>> I hope not, given that leaving the SuperIO decoding enable allows
>>>> the
>>>> host to (slowly) scrape BMC memory (or if iLPC2AHB writes are
>>>> allowed,
>>>> open faster backdoors). We should root-cause the issue before
>>>> exploring this path.
>>>>
>>>> Andrew

milton