mtd: add support for switching old SST chips into QRY mode

SST 39VF160x/39VF320x and some old SST chips need a special command
sequence to enter CFI QueRY mode [1].
This patch adds the relevant sequence to cfi_qry_mode_on().
Tested with 39VF3201.
Signed-off-by: Guillaume LECERF <glecerf@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/chips/cfi_util.c

@@ -69,6 +69,13 @@ int __xipram cfi_qry_mode_on(uint32_t base, struct map_info *map,
 	/* ST M29DW chips */
 	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
 	cfi_send_gen_cmd(0x98, 0x555, base, map, cfi, cfi->device_type, NULL);
+	if (cfi_qry_present(map, base, cfi))
+		return 1;
+	/* some old SST chips, e.g. 39VF160x/39VF320x */
+	cfi_send_gen_cmd(0xF0, 0, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0xAA, 0x5555, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0x55, 0x2AAA, base, map, cfi, cfi->device_type, NULL);
+	cfi_send_gen_cmd(0x98, 0x5555, base, map, cfi, cfi->device_type, NULL);
 	if (cfi_qry_present(map, base, cfi))
 		return 1;
 	/* QRY not found */