On Tue, Apr 19, 2016 at 01:07:59PM +1000, Alexey Kardashevskiy wrote: >On 02/17/2016 02:44 PM, Gavin Shan wrote: >>PE number for one particular PE can be allocated dynamically or >>reserved according to the consumed M64 (64-bits prefetchable) >>segments of the PE. The M64 resources, and hence their segments >>and PE number are assigned/reserved in ascending order. The PE >>numbers are allocated dynamically in ascending order as well. >>It's not a problem as the PE numbers are reserved and then >>allocated all at once in fine order. However, it will introduce >>conflicts when PCI hotplug is supported: the PE number to be >>reserved for newly added PE might have been assigned. >> >>To resolve above conflicts, this forces the PE number to be >>allocated dynamically in reverse order. With this patch applied, >>the PE numbers are reserved in ascending order, but allocated >>dynamically in reverse order. > > >The patch is probably is ok, the commit log is not - I do not follow it. Some >PEs are reserved (for what? why does the absolute PE number matter? put it in >the commit log), that means that the corresponding bits in pe_alloc[] should >be set so when you will be allocating PEs for a just plugged device, you >won't pick them and you will pick free ones, and the order should not matter. >I would think that "reservation" happens once at the boot time so you set >"used" bits for the reserved PEs then and after that the dynamic allocator >will skip them. > I will enhance the commit log in next revision, perhaps just pick part of below words: On PHB3, there are 16 M64 BARs in hardware. The last one is split ovenly into 256 segments. Each segment can be associated/assigned to fixed PE# (segment#x <-> PE#x) which is how the hardware was designed. If one plugged PE has M64 (64-bits prefetchable memory) resources, its PE# is equal to the segment#. Otherwise, the PE# is allocated dynamically if the PE doesn't contain M64 resource. The M64 resources are assigned from low to high end, meaning the reserved PE# (according to the M64 segments) are grown from low to high end. It's most likely to get a dynamically allocated PE# which should be reserved because of M64 segment. It's the conflicts the patch tries to resolve. The PE# reservation doesn't happen once at boot time because it's unknow how many PEs and how much M64 resources will be hot added. > >> >>Signed-off-by: Gavin Shan <gwshan@xxxxxxxxxxxxxxxxxx> >>--- >> arch/powerpc/platforms/powernv/pci-ioda.c | 14 ++++++-------- >> 1 file changed, 6 insertions(+), 8 deletions(-) >> >>diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c >>index f182ca7..565725b 100644 >>--- a/arch/powerpc/platforms/powernv/pci-ioda.c >>+++ b/arch/powerpc/platforms/powernv/pci-ioda.c >>@@ -144,16 +144,14 @@ static void 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 pe = 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) >>- return NULL; >>- } while(test_and_set_bit(pe, phb->ioda.pe_alloc)); >>+ for (pe = phb->ioda.total_pe_num - 1; pe >= 0; pe--) { >>+ if (!test_and_set_bit(pe, phb->ioda.pe_alloc)) >>+ return pnv_ioda_init_pe(phb, pe); >>+ } >> >>- return pnv_ioda_init_pe(phb, pe); >>+ return NULL; >> } >> >> static void pnv_ioda_free_pe(struct pnv_ioda_pe *pe) >> > > >-- >Alexey > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html