Re: [PATCH v6 18/42] powerpc/powernv: Allocate PE# in deasending order

Alexey Kardashevskiy
2015-08-11T02:50:33Z

On 08/11/2015 10:43 AM, Gavin Shan wrote:
> On Tue, Aug 11, 2015 at 12:39:02AM +1000, Alexey Kardashevskiy wrote:
>> On 08/06/2015 02:11 PM, Gavin Shan wrote:
>>> The available PE#, represented by a bitmap in the PHB, is allocated
>>> in ascending order.
>>
>> Available PE# is available exactly because it is not allocated ;)
>>
>
> Yeah, will correct it.
>
>>> It conflicts with the fact that M64 segments are
>>> assigned in same order. In order to avoid the conflict, the patch
>>> allocates PE# in descending order.
>>
>> What kind of conflict?
>>
>
> On PHB3, the M64 segment is assigned to one PE whose PE number is
> determined. M64 segment are allocated in ascending order. It's why
> I would like to allocate PE# in deascending order.

From previous lessons, I thought M64 segment number is PE# number as well :-/
Seems this is not the case, so what does store this seg#<->PE# mapping in PHB?

>
>>>
>>> Signed-off-by: Gavin Shan <gwshan@linux.vnet.ibm.com>
>>> ---
>>> arch/powerpc/platforms/powernv/pci-ioda.c | 11 ++++++++---
>>> 1 file changed, 8 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
>>> index 56b058c..1c950e8 100644
>>> --- a/arch/powerpc/platforms/powernv/pci-ioda.c
>>> +++ b/arch/powerpc/platforms/powernv/pci-ioda.c
>>> @@ -161,13 +161,18 @@ static struct pnv_ioda_pe *pnv_ioda_reserve_pe(struct pnv_phb *phb, int pe_no)
>>> static struct pnv_ioda_pe *pnv_ioda_alloc_pe(struct pnv_phb *phb)
>>> {
>>> unsigned long pe;
>>> + unsigned long limit = phb->ioda.total_pe_num - 1;
>>>
>>> do {
>>> pe = find_next_zero_bit(phb->ioda.pe_alloc,
>>> - phb->ioda.total_pe_num, 0);
>>> - if (pe >= phb->ioda.total_pe_num)
>>> + phb->ioda.total_pe_num, limit);
>>> + if (pe < phb->ioda.total_pe_num &&
>>> + !test_and_set_bit(pe, phb->ioda.pe_alloc))
>>> + break;
>>> +
>>> + if (--limit >= phb->ioda.total_pe_num)
>>> return NULL;
>>> - } while(test_and_set_bit(pe, phb->ioda.pe_alloc));
>>> + } while (1);
>>
>>
>> Usually, if it is "while(1)", then it is "while(1){}" rather than
>> "do{}while(1)" :)
>
> Agree, will change it.
>
>>
>>
>>>
>>> return pnv_ioda_init_pe(phb, pe);
>>> }
>>>
>
> Thanks,
> Gavin
>

--
Alexey