powerpc: pci-ioda: Optimize pnv_ioda_pick_m64_pe()

bitmap_empty() in pnv_ioda_pick_m64_pe() is O(N) and useless because
the following find_next_bit() does the same work.

Drop it, and while there replace a while() loop with the dedicated
for_each_set_bit().

Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Yury Norov (NVIDIA) <yury.norov@gmail.com>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/20250814190936.381346-3-yury.norov@gmail.com

diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 83f75d88e53b8acac5cd8618870f8ac3ae37bde9..32ecbc46e74b9d4d6d835a8bfd86f00d74fd7d5b 100644 (file)
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -295,7 +295,7 @@ static struct pnv_ioda_pe *pnv_ioda_pick_m64_pe(struct pci_bus *bus, bool all)
        unsigned long *pe_alloc __free(bitmap) = NULL;
        struct pnv_phb *phb = pci_bus_to_pnvhb(bus);
        struct pnv_ioda_pe *master_pe, *pe;
-       int i;
+       unsigned int i;
 
        /* Root bus shouldn't use M64 */
        if (pci_is_root_bus(bus))
@@ -311,23 +311,16 @@ static struct pnv_ioda_pe *pnv_ioda_pick_m64_pe(struct pci_bus *bus, bool all)
        /* Figure out reserved PE numbers by the PE */
        pnv_ioda_reserve_m64_pe(bus, pe_alloc, all);
 
-       /*
-        * the current bus might not own M64 window and that's all
-        * contributed by its child buses. For the case, we needn't
-        * pick M64 dependent PE#.
-        */
-       if (bitmap_empty(pe_alloc, phb->ioda.total_pe_num)) {
-               return NULL;
-       }
-
        /*
         * Figure out the master PE and put all slave PEs to master
         * PE's list to form compound PE.
+        *
+        * The current bus might not own M64 window and that's all
+        * contributed by its child buses. For the case, we needn't
+        * pick M64 dependent PE#.
         */
        master_pe = NULL;
-       i = -1;
-       while ((i = find_next_bit(pe_alloc, phb->ioda.total_pe_num, i + 1)) <
-               phb->ioda.total_pe_num) {
+       for_each_set_bit(i, pe_alloc, phb->ioda.total_pe_num) {
                pe = &phb->ioda.pe_array[i];
 
                phb->ioda.m64_segmap[pe->pe_number] = pe->pe_number;