sh: Allocate PMB entry slot earlier

Simplify set_pmb_entry() by removing the possibility of not finding a
free slot in the PMB. Instead we now allocate a slot in pmb_alloc() so
that if there are no free slots we fail at allocation time, rather than
in set_pmb_entry().

Signed-off-by: Matt Fleming <matt@console-pimps.org>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>

1 files changed, 39 insertions, 41 deletions

diff --git a/arch/sh/mm/pmb.c b/arch/sh/mm/pmb.c
index aade31102112..b8a33949296a 100644
--- a/arch/sh/mm/pmb.c
+++ b/arch/sh/mm/pmb.c
@@ -99,10 +99,31 @@ static inline void pmb_list_del(struct pmb_entry *pmbe)
                 }
 }
 
+static int pmb_alloc_entry(void)
+{
+        unsigned int pos;
+
+repeat:
+        pos = find_first_zero_bit(&pmb_map, NR_PMB_ENTRIES);
+
+        if (unlikely(pos > NR_PMB_ENTRIES))
+                return -ENOSPC;
+
+        if (test_and_set_bit(pos, &pmb_map))
+                goto repeat;
+
+        return pos;
+}
+
 struct pmb_entry *pmb_alloc(unsigned long vpn, unsigned long ppn,
                             unsigned long flags)
 {
         struct pmb_entry *pmbe;
+        int pos;
+
+        pos = pmb_alloc_entry();
+        if (pos < 0)
+                return ERR_PTR(pos);
 
         pmbe = kmem_cache_alloc(pmb_cache, GFP_KERNEL);
         if (!pmbe)
@@ -111,6 +132,7 @@ struct pmb_entry *pmb_alloc(unsigned long vpn, unsigned long ppn,
         pmbe->vpn       = vpn;
         pmbe->ppn       = ppn;
         pmbe->flags     = flags;
+        pmbe->entry     = pos;
 
         spin_lock_irq(&pmb_list_lock);
         pmb_list_add(pmbe);
@@ -131,23 +153,9 @@ void pmb_free(struct pmb_entry *pmbe)
 /*
  * Must be in P2 for __set_pmb_entry()
  */
-int __set_pmb_entry(unsigned long vpn, unsigned long ppn,
-                    unsigned long flags, int *entry)
+void __set_pmb_entry(unsigned long vpn, unsigned long ppn,
+                    unsigned long flags, int pos)
 {
-        unsigned int pos = *entry;
-
-        if (unlikely(pos == PMB_NO_ENTRY))
-                pos = find_first_zero_bit(&pmb_map, NR_PMB_ENTRIES);
-
-repeat:
-        if (unlikely(pos > NR_PMB_ENTRIES))
-                return -ENOSPC;
-
-        if (test_and_set_bit(pos, &pmb_map)) {
-                pos = find_first_zero_bit(&pmb_map, NR_PMB_ENTRIES);
-                goto repeat;
-        }
-
         ctrl_outl(vpn | PMB_V, mk_pmb_addr(pos));
 
 #ifdef CONFIG_CACHE_WRITETHROUGH
@@ -161,21 +169,13 @@ repeat:
 #endif
 
         ctrl_outl(ppn | flags | PMB_V, mk_pmb_data(pos));
-
-        *entry = pos;
-
-        return 0;
 }
 
-int __uses_jump_to_uncached set_pmb_entry(struct pmb_entry *pmbe)
+void __uses_jump_to_uncached set_pmb_entry(struct pmb_entry *pmbe)
 {
-        int ret;
-
         jump_to_uncached();
-        ret = __set_pmb_entry(pmbe->vpn, pmbe->ppn, pmbe->flags, &pmbe->entry);
+        __set_pmb_entry(pmbe->vpn, pmbe->ppn, pmbe->flags, pmbe->entry);
         back_to_cached();
-
-        return ret;
 }
 
 void __uses_jump_to_uncached clear_pmb_entry(struct pmb_entry *pmbe)
@@ -239,8 +239,6 @@ long pmb_remap(unsigned long vaddr, unsigned long phys,
 
 again:
         for (i = 0; i < ARRAY_SIZE(pmb_sizes); i++) {
-                int ret;
-
                 if (size < pmb_sizes[i].size)
                         continue;
 
@@ -250,12 +248,7 @@ again:
                         goto out;
                 }
 
-                ret = set_pmb_entry(pmbe);
-                if (ret != 0) {
-                        pmb_free(pmbe);
-                        err = -EBUSY;
-                        goto out;
-                }
+                set_pmb_entry(pmbe);
 
                 phys    += pmb_sizes[i].size;
                 vaddr   += pmb_sizes[i].size;
@@ -311,8 +304,17 @@ static void __pmb_unmap(struct pmb_entry *pmbe)
         do {
                 struct pmb_entry *pmblink = pmbe;
 
-                if (pmbe->entry != PMB_NO_ENTRY)
-                        clear_pmb_entry(pmbe);
+                /*
+                 * We may be called before this pmb_entry has been
+                 * entered into the PMB table via set_pmb_entry(), but
+                 * that's OK because we've allocated a unique slot for
+                 * this entry in pmb_alloc() (even if we haven't filled
+                 * it yet).
+                 *
+                 * Therefore, calling clear_pmb_entry() is safe as no
+                 * other mapping can be using that slot.
+                 */
+                clear_pmb_entry(pmbe);
 
                 pmbe = pmblink->link;
 
@@ -322,11 +324,7 @@ static void __pmb_unmap(struct pmb_entry *pmbe)
 
 static void pmb_cache_ctor(void *pmb)
 {
-        struct pmb_entry *pmbe = pmb;
-
         memset(pmb, 0, sizeof(struct pmb_entry));
-
-        pmbe->entry = PMB_NO_ENTRY;
 }
 
 static int __uses_jump_to_uncached pmb_init(void)
@@ -349,7 +347,7 @@ static int __uses_jump_to_uncached pmb_init(void)
         for (entry = 0; entry < nr_entries; entry++) {
                 struct pmb_entry *pmbe = pmb_init_map + entry;
 
-                __set_pmb_entry(pmbe->vpn, pmbe->ppn, pmbe->flags, &entry);
+                __set_pmb_entry(pmbe->vpn, pmbe->ppn, pmbe->flags, entry);
         }
 
         ctrl_outl(0, PMB_IRMCR);