ARM: OMAP: Cleanup OMAP FB SDRAM reservation

The logic in this file is rather convoluted, but essentially:

1. region type 0 is SDRAM
2. referring to the code fragment
                if (set_fbmem_region_type(&rg, OMAPFB_MEMTYPE_SDRAM,
                                          sdram_start, sdram_size) < 0 ||
                    (rg.type != OMAPFB_MEMTYPE_SDRAM))
                        continue;
   - if rg.type is not OMAPFB_MEMTYPE_SDRAM, set_fbmem_region_type()
     returns zero immediately (since rg.type is non-zero), and so we
     'continue'.
   - if rg.type is OMAPFB_MEMTYPE_SDRAM, and rg.paddr is zero,
     we fall through.
   - if rg.type is OMAPFB_MEMTYPE_SDRAM, and the region lies within
     SDRAM, we fall through.
   - if rg.type is OMAPFB_MEMTYPE_SDRAM, and the region is not within
     SDRAM, we 'continue'.
3. check_fbmem_region seems unnecessary.
   - we know rg.type is OMAPFB_MEMTYPE_SDRAM
   - we can check rg.size independently
   - bootmem_reserve() can check for overlapping reservations itself
   - we've already validated that the requested region lies within SDRAM.
4. avoid BUG()ing if the region entry is already set; print an error,
   and mark the configuration invalid - at least we'll continue booting
   so the error message has a chance of being logged/visible via serial
   console.

With these changes in place, it makes the code much easier to understand
and hence easier to convert to LMB.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 44 insertions, 17 deletions

diff --git a/arch/arm/plat-omap/fb.c b/arch/arm/plat-omap/fb.c
index d3eea4f47533..97db493904fa 100644
--- a/arch/arm/plat-omap/fb.c
+++ b/arch/arm/plat-omap/fb.c
@@ -171,49 +171,76 @@ static int check_fbmem_region(int region_idx, struct omapfb_mem_region *rg,
         return 0;
 }
 
+static int valid_sdram(unsigned long addr, unsigned long size)
+{
+        struct bootmem_data *bdata = NODE_DATA(0)->bdata;
+        unsigned long sdram_start, sdram_end;
+
+        sdram_start = bdata->node_min_pfn << PAGE_SHIFT;
+        sdram_end = bdata->node_low_pfn << PAGE_SHIFT;
+
+        return addr >= sdram_start && sdram_end - addr >= size;
+}
+
+static int reserve_sdram(unsigned long addr, unsigned long size)
+{
+        return reserve_bootmem(addr, size, BOOTMEM_EXCLUSIVE);
+}
+
 /*
  * Called from map_io. We need to call to this early enough so that we
  * can reserve the fixed SDRAM regions before VM could get hold of them.
  */
 void __init omapfb_reserve_sdram(void)
 {
-        struct bootmem_data     *bdata;
-        unsigned long           sdram_start, sdram_size;
-        unsigned long           reserved;
-        int                     i;
+        unsigned long reserved = 0;
+        int i;
 
         if (config_invalid)
                 return;
 
-        bdata = NODE_DATA(0)->bdata;
-        sdram_start = bdata->node_min_pfn << PAGE_SHIFT;
-        sdram_size = (bdata->node_low_pfn << PAGE_SHIFT) - sdram_start;
-        reserved = 0;
         for (i = 0; ; i++) {
-                struct omapfb_mem_region        rg;
+                struct omapfb_mem_region rg;
 
                 if (get_fbmem_region(i, &rg) < 0)
                         break;
+
                 if (i == OMAPFB_PLANE_NUM) {
-                        printk(KERN_ERR
-                                "Extraneous FB mem configuration entries\n");
+                        pr_err("Extraneous FB mem configuration entries\n");
                         config_invalid = 1;
                         return;
                 }
+
                 /* Check if it's our memory type. */
-                if (set_fbmem_region_type(&rg, OMAPFB_MEMTYPE_SDRAM,
-                                          sdram_start, sdram_size) < 0 ||
-                    (rg.type != OMAPFB_MEMTYPE_SDRAM))
+                if (rg.type != OMAPFB_MEMTYPE_SDRAM)
                         continue;
-                BUG_ON(omapfb_config.mem_desc.region[i].size);
-                if (check_fbmem_region(i, &rg, sdram_start, sdram_size) < 0) {
+
+                /* Check if the region falls within SDRAM */
+                if (rg.paddr && !valid_sdram(rg.paddr, rg.size))
+                        continue;
+
+                if (rg.size == 0) {
+                        pr_err("Zero size for FB region %d\n", i);
                         config_invalid = 1;
                         return;
                 }
+
                 if (rg.paddr) {
-                        reserve_bootmem(rg.paddr, rg.size, BOOTMEM_DEFAULT);
+                        if (reserve_sdram(rg.paddr, rg.size)) {
+                                pr_err("Trying to use reserved memory for FB region %d\n",
+                                        i);
+                                config_invalid = 1;
+                                return;
+                        }
                         reserved += rg.size;
                 }
+
+                if (omapfb_config.mem_desc.region[i].size) {
+                        pr_err("FB region %d already set\n", i);
+                        config_invalid = 1;
+                        return;
+                }
+
                 omapfb_config.mem_desc.region[i] = rg;
                 configured_regions++;
         }