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

From: Gavin Shan <[email-masked]>
Date: Tue, 11 Aug 2015 10:43:39 +1000

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.

>>
>>Signed-off-by: Gavin Shan <[email-masked]>
>>---
>>  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