mtd: cfi_cmdset_0002: do not fail on no extended query table as they are both optional

After looking at AMD's CFI specification [1], both of the extended query
tables are optional. Thus, it looks like relying that at least one of
those tables exist is a bug in cfi_cmdset_0002.

This patch inverts the logic and checks for unlock function pointers before
exiting on error. This approach leaves place to add a call to a fixup
function to try to handle chips compatible with the early AMD specification
from 1995 [2].

[1] http://www.amd.com/us-en/assets/content_type/DownloadableAssets/cfi_r20.pdf
[2] http://noel.feld.cvut.cz/hw/amd/20158a.pdf

Signed-off-by: Guillaume LECERF <glecerf@gmail.com>
Reviewed-by: Wolfram Sang <w.sang@pengutronix.de>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

1 files changed, 45 insertions, 44 deletions

diff --git a/drivers/mtd/chips/cfi_cmdset_0002.c b/drivers/mtd/chips/cfi_cmdset_0002.c
index c16b8cecc3a8..ce38d3d049ef 100644
--- a/drivers/mtd/chips/cfi_cmdset_0002.c
+++ b/drivers/mtd/chips/cfi_cmdset_0002.c
@@ -357,65 +357,66 @@ struct mtd_info *cfi_cmdset_0002(struct map_info *map, int primary)
 
         if (cfi->cfi_mode==CFI_MODE_CFI){
                 unsigned char bootloc;
-                /*
-                 * It's a real CFI chip, not one for which the probe
-                 * routine faked a CFI structure. So we read the feature
-                 * table from it.
-                 */
                 __u16 adr = primary?cfi->cfiq->P_ADR:cfi->cfiq->A_ADR;
                 struct cfi_pri_amdstd *extp;
 
                 extp = (struct cfi_pri_amdstd*)cfi_read_pri(map, adr, sizeof(*extp), "Amd/Fujitsu");
-                if (!extp) {
-                        kfree(mtd);
-                        return NULL;
-                }
-
-                cfi_fixup_major_minor(cfi, extp);
-
-                if (extp->MajorVersion != '1' ||
-                    (extp->MinorVersion < '0' || extp->MinorVersion > '4')) {
-                        printk(KERN_ERR "  Unknown Amd/Fujitsu Extended Query "
-                               "version %c.%c.\n",  extp->MajorVersion,
-                               extp->MinorVersion);
-                        kfree(extp);
-                        kfree(mtd);
-                        return NULL;
-                }
+                if (extp) {
+                        /*
+                         * It's a real CFI chip, not one for which the probe
+                         * routine faked a CFI structure.
+                         */
+                        cfi_fixup_major_minor(cfi, extp);
+
+                        if (extp->MajorVersion != '1' ||
+                            (extp->MinorVersion < '0' || extp->MinorVersion > '4')) {
+                                printk(KERN_ERR "  Unknown Amd/Fujitsu Extended Query "
+                                       "version %c.%c.\n",  extp->MajorVersion,
+                                       extp->MinorVersion);
+                                kfree(extp);
+                                kfree(mtd);
+                                return NULL;
+                        }
 
-                /* Install our own private info structure */
-                cfi->cmdset_priv = extp;
+                        /* Install our own private info structure */
+                        cfi->cmdset_priv = extp;
 
-                /* Apply cfi device specific fixups */
-                cfi_fixup(mtd, cfi_fixup_table);
+                        /* Apply cfi device specific fixups */
+                        cfi_fixup(mtd, cfi_fixup_table);
 
 #ifdef DEBUG_CFI_FEATURES
-                /* Tell the user about it in lots of lovely detail */
-                cfi_tell_features(extp);
+                        /* Tell the user about it in lots of lovely detail */
+                        cfi_tell_features(extp);
 #endif
 
-                bootloc = extp->TopBottom;
-                if ((bootloc != 2) && (bootloc != 3)) {
-                        printk(KERN_WARNING "%s: CFI does not contain boot "
-                               "bank location. Assuming top.\n", map->name);
-                        bootloc = 2;
-                }
+                        bootloc = extp->TopBottom;
+                        if ((bootloc != 2) && (bootloc != 3)) {
+                                printk(KERN_WARNING "%s: CFI does not contain boot "
+                                       "bank location. Assuming top.\n", map->name);
+                                bootloc = 2;
+                        }
 
-                if (bootloc == 3 && cfi->cfiq->NumEraseRegions > 1) {
-                        printk(KERN_WARNING "%s: Swapping erase regions for broken CFI table.\n", map->name);
+                        if (bootloc == 3 && cfi->cfiq->NumEraseRegions > 1) {
+                                printk(KERN_WARNING "%s: Swapping erase regions for broken CFI table.\n", map->name);
 
-                        for (i=0; i<cfi->cfiq->NumEraseRegions / 2; i++) {
-                                int j = (cfi->cfiq->NumEraseRegions-1)-i;
-                                __u32 swap;
+                                for (i=0; i<cfi->cfiq->NumEraseRegions / 2; i++) {
+                                        int j = (cfi->cfiq->NumEraseRegions-1)-i;
+                                        __u32 swap;
 
-                                swap = cfi->cfiq->EraseRegionInfo[i];
-                                cfi->cfiq->EraseRegionInfo[i] = cfi->cfiq->EraseRegionInfo[j];
-                                cfi->cfiq->EraseRegionInfo[j] = swap;
+                                        swap = cfi->cfiq->EraseRegionInfo[i];
+                                        cfi->cfiq->EraseRegionInfo[i] = cfi->cfiq->EraseRegionInfo[j];
+                                        cfi->cfiq->EraseRegionInfo[j] = swap;
+                                }
                         }
+                        /* Set the default CFI lock/unlock addresses */
+                        cfi->addr_unlock1 = 0x555;
+                        cfi->addr_unlock2 = 0x2aa;
+                }
+
+                if (!cfi->addr_unlock1 || !cfi->addr_unlock2) {
+                        kfree(mtd);
+                        return NULL;
                 }
-                /* Set the default CFI lock/unlock addresses */
-                cfi->addr_unlock1 = 0x555;
-                cfi->addr_unlock2 = 0x2aa;
 
         } /* CFI mode */
         else if (cfi->cfi_mode == CFI_MODE_JEDEC) {