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

On Tue, Aug 11, 2015 at 12:39:02AM +1000, Alexey Kardashevskiy wrote:

On 08/06/2015 02:11 PM, Gavin Shan wrote:

quoted

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.

quoted

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.

quoted

Signed-off-by: Gavin Shan <redacted>
---
 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.

quoted

 	return pnv_ioda_init_pe(phb, pe);
 }

Thanks,
Gavin