[PATCH kernel v3 0/3] powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59

[Shawn Anastasio]

On 6/12/19 2:15 PM, Shawn Anastasio wrote:
> On 6/12/19 2:07 AM, Alexey Kardashevskiy wrote:
>>
>>
>> On 12/06/2019 15:05, Shawn Anastasio wrote:
>>> On 6/5/19 11:11 PM, Shawn Anastasio wrote:
>>>> On 5/30/19 2:03 AM, Alexey Kardashevskiy wrote:
>>>>> This is an attempt to allow DMA masks between 32..59 which are not 
>>>>> large
>>>>> enough to use either a PHB3 bypass mode or a sketchy bypass. Depending
>>>>> on the max order, up to 40 is usually available.
>>>>>
>>>>>
>>>>> This is based on v5.2-rc2.
>>>>>
>>>>> Please comment. Thanks.
>>>>
>>>> I have tested this patch set with an AMD GPU that's limited to <64bit
>>>> DMA (I believe it's 40 or 42 bit). It successfully allows the card to
>>>> operate without falling back to 32-bit DMA mode as it does without
>>>> the patches.
>>>>
>>>> Relevant kernel log message:
>>>> ```
>>>> [    0.311211] pci 0033:01     : [PE# 00] Enabling 64-bit DMA bypass
>>>> ```
>>>>
>>>> Tested-by: Shawn Anastasio <shawn at anastas.io>
>>>
>>> After a few days of further testing, I've started to run into stability
>>> issues with the patch applied and used with an AMD GPU. Specifically,
>>> the system sometimes spontaneously crashes. Not just EEH errors either,
>>> the whole system shuts down in what looks like a checkstop.
>>>
>>> Perhaps some subtle corruption is occurring?
>>
>> Have you tried this?
>>
>> https://patchwork.ozlabs.org/patch/1113506/
> 
> I have not. I'll give it a shot and try it out for a few days to see
> if I'm able to reproduce the crashes.

A few days later and I was able to reproduce the checkstop while
watching a video in mpv. At this point the system had ~4 day
uptime and this wasn't the first video I watched during that time.

This is with https://patchwork.ozlabs.org/patch/1113506/ applied, too.