[PATCH v2 17/39] sandbox: Implement reference counting for address mapping

[Simon Glass]

An address may be mapped twice and unmapped twice. Delete the mapping
only when the last user unmaps it.

Fix a missing comment while here.

Signed-off-by: Simon Glass <s...@chromium.org>
---

(no changes since v1)

 arch/sandbox/cpu/cpu.c           | 14 ++++++++++----
 arch/sandbox/include/asm/state.h |  3 +++
 2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/arch/sandbox/cpu/cpu.c b/arch/sandbox/cpu/cpu.c
index ac00be16cd7..7a4621f7e40 100644
--- a/arch/sandbox/cpu/cpu.c
+++ b/arch/sandbox/cpu/cpu.c
@@ -111,6 +111,7 @@ void *phys_to_virt(phys_addr_t paddr)
                if (mentry->tag == paddr) {
                        log_debug("Used map from %lx to %p\n", (ulong)paddr,
                                  mentry->ptr);
+                       mentry->refcnt++;
                        return mentry->ptr;
                }
        }
@@ -200,10 +201,12 @@ void unmap_physmem(const void *ptr, unsigned long flags)
 
        mentry = find_tag(ptr);
        if (mentry) {
-               list_del(&mentry->sibling_node);
-               log_debug("Removed map from %p to %lx\n", ptr,
-                         (ulong)mentry->tag);
-               free(mentry);
+               if (!--mentry->refcnt) {
+                       list_del(&mentry->sibling_node);
+                       log_debug("Removed map from %p to %lx\n", ptr,
+                                 (ulong)mentry->tag);
+                       free(mentry);
+               }
        } else {
                log_warning("Address not mapped: %p\n", ptr);
        }
@@ -235,11 +238,14 @@ phys_addr_t map_to_sysmem(const void *ptr)
                }
                mentry->tag = state->next_tag++;
                mentry->ptr = (void *)ptr;
+               mentry->refcnt = 0;
                list_add_tail(&mentry->sibling_node, &state->mapmem_head);
                log_debug("Added map from %p to %lx\n", ptr,
                          (ulong)mentry->tag);
        }
 
+       mentry->refcnt++;
+
        /*
         * Return the tag as the address to use. A later call to map_sysmem()
         * will return ptr
diff --git a/arch/sandbox/include/asm/state.h b/arch/sandbox/include/asm/state.h
index c84a1f7060f..8213e61c3ce 100644
--- a/arch/sandbox/include/asm/state.h
+++ b/arch/sandbox/include/asm/state.h
@@ -53,10 +53,13 @@ struct sandbox_wdt_info {
  * be returned, just as it would for a normal sandbox address.
  *
  * @tag: Address tag (a value which U-Boot uses to refer to the address)
+ * @refcnt: Number of references to this tag
  * @ptr: Associated pointer for that tag
+ * @sibling_node: Next node
  */
 struct sandbox_mapmem_entry {
        ulong tag;
+       uint refcnt;
        void *ptr;
        struct list_head sibling_node;
 };
-- 
2.34.1