[Skiboot] [PATCH 3/3] xscom: Do not wait indefinitely for xscom operation to complete

[Vasant Hegde]

On 5/20/20 8:54 PM, Vasant Hegde wrote:
> On 5/20/20 7:43 PM, Nicholas Piggin wrote:
>> Excerpts from Vasant Hegde's message of May 20, 2020 9:51 pm:
>>> In some corner cases (specially on P8), xscom_wait_done() won't
>>> complete.. resulting in waiting forever.
>>>
>>> This patch retries for predefined time and then exits even if xscom
>>> operation did not complete.
>>>
>>> Signed-off-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
>>> ---
>>>   hw/xscom.c | 7 +++++--
>>>   1 file changed, 5 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/hw/xscom.c b/hw/xscom.c
>>> index 0eda567fc..500b6c0e9 100644
>>> --- a/hw/xscom.c
>>> +++ b/hw/xscom.c
>>> @@ -72,10 +72,13 @@ static inline void *xscom_addr(uint32_t gcid, uint32_t 
>>> pcb_addr)
>>>   static uint64_t xscom_wait_done(void)
>>>   {
>>>       uint64_t hmer;
>>> +    int retry_cnt = 0;
>>> -    do
>>> +    do {
>>>           hmer = mfspr(SPR_HMER);
>>> -    while(!(hmer & SPR_HMER_XSCOM_DONE));
>>> +        if (retry_cnt++ > 5)
>>> +            break;
>>
>> AFAIKS you'd better return SPR_HMER_XSCOM_FAIL here.
> 
> Makes sense. Will fix it in v2.

We pass return value from this function to handle_error() .. which uses this 
value for isolating error.
So I think it makes sense to just return `hmer` value.


-Vasant