phosphor-isolation

[James Feist]

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.
> 
> (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
>