bcm53xx: hack UBI to erase all dirty blocks left by CFE

UBI requires PEBs to be formatted (with a valid UBI header) or empty
(0xFF), however CFE doesn't clear blocks after flashing the image. To
workaround this problem, teach UBI to recognize EOF mark in a similar
way JFFS2 handles that in OpenWrt.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>

SVN-Revision: 42940

target/linux/bcm53xx/patches-3.14/500-UBI-Detect-EOF-mark-and-erase-all-remaining-blocks.patch

@@ -0,0 +1,39 @@
+From f41f8b42db092e505382f7120994de21590dff48 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Rafa=C5=82=20Mi=C5=82ecki?= <zajec5@gmail.com>
+Date: Thu, 16 Oct 2014 20:52:16 +0200
+Subject: [PATCH] UBI: Detect EOF mark and erase all remaining blocks
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
+---
+ drivers/mtd/ubi/io.c | 5 +++++
+ 1 file changed, 5 insertions(+)
+
+diff --git a/drivers/mtd/ubi/io.c b/drivers/mtd/ubi/io.c
+index d361349..f9bba3c 100644
+--- a/drivers/mtd/ubi/io.c
++++ b/drivers/mtd/ubi/io.c
+@@ -727,6 +727,7 @@ bad:
+  * o %UBI_IO_FF if only 0xFF bytes were read (the PEB is supposedly empty)
+  * o a negative error code in case of failure.
+  */
++static bool erase_all_next = false;
+ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
+ 		       struct ubi_ec_hdr *ec_hdr, int verbose)
+ {
+@@ -753,6 +754,10 @@ int ubi_io_read_ec_hdr(struct ubi_device *ubi, int pnum,
+ 	}
+ 
+ 	magic = be32_to_cpu(ec_hdr->magic);
++	if (magic == 0xdeadc0de)
++		erase_all_next = true;
++	if (erase_all_next)
++		return read_err ? UBI_IO_FF_BITFLIPS : UBI_IO_FF;
+ 	if (magic != UBI_EC_HDR_MAGIC) {
+ 		if (mtd_is_eccerr(read_err))
+ 			return UBI_IO_BAD_HDR_EBADMSG;
+-- 
+1.8.4.5
+