[Skiboot] [PATCH-RESEND] capi: Disable CAPP virtual machines

[Stewart Smith]

christophe lombard <clombard at linux.vnet.ibm.com> writes:
> Le 18/01/2018 à 05:09, Vaibhav Jain a écrit :
>> When exercising more than one CAPI accelerators simultaneously in
>> cache coherency mode, the verification team is seeing a deadlock. To
>> fix this a workaround of disabling CAPP virtual machines is
>> suggested. These 'virtual machines' let PSL queue multiple CAPP
>> commands for servicing by CAPP there by increasing
>> throughput. Below is the error scenario described by the h/w team:
>> 
>> " With virtual machines enabled we had a deadlock scenario where with 2
>> or more CAPI's in a system you could get in a deadlock scenario due to
>> cast-outs that are required break the deadlock (evict lines that
>> another CAPI is requesting) get stuck in the virtual machine queue by
>> a command ahead of it that is being retried by the same scenario in
>> the other CAPI. "
>> 
>> So this patch updates CAPP APC Master Powerbus control
>> register during CAPP init to also set Bit(12) that disables CAPP
>> virtual machines. This forces processing of CAPP commands from PSL one
>> at a time and thereby preventing above mentioned deadlock scenario.
>> 
>> Signed-off-by: Vaibhav Jain <vaibhav at linux.vnet.ibm.com>
>> ---
>> Change-log:
>> Resend -> Updated the patch description with more info CAPP virtual
>>         	  machines and the error scenario.
>> ---
>>   hw/phb4.c | 1 +
>>   1 file changed, 1 insertion(+)
>> 
>> diff --git a/hw/phb4.c b/hw/phb4.c
>> index ff912e1f..8e660b66 100644
>> --- a/hw/phb4.c
>> +++ b/hw/phb4.c
>> @@ -3581,6 +3581,7 @@ static void phb4_init_capp_regs(struct phb4 *p, uint32_t capp_eng)
>>   	xscom_read(p->chip_id, APC_MASTER_PB_CTRL + offset, &reg);
>>   	reg |= PPC_BIT(0); /* enable cResp exam */
>>   	reg |= PPC_BIT(3); /* disable vg not sys */
>> +	reg |= PPC_BIT(12);/* HW417025: disable capp virtual machines */
>>   	if (p->rev == PHB4_REV_NIMBUS_DD10) {
>>   		reg |= PPC_BIT(1);
>>   	} else {
>> 
>
> Acked-by: Christophe Lombard clombard at linux.vnet.ibm.com

You seem to be missing the < > around the email address, which caused
patchwork not to pick up the acked-by. Might want to fix that :)

-- 
Stewart Smith
OPAL Architect, IBM.