[flashrom-gerrit] Change in flashrom[master]: linux_mtd: Support for NO_ERASE type devices

[David Hendricks (Code Review)]

Hello Brian Norris,

I'd like you to do a code review. Please visit

https://review.coreboot.org/22511

to review the following change.

Change subject: linux_mtd: Support for NO_ERASE type devices
......................................................................

linux_mtd: Support for NO_ERASE type devices

Some mtd devices have the MTD_NO_ERASE flag set. This means
these devices don't require an erase to write and might not have
implemented an erase function. We should be conservative and skip
erasing altogether, falling back to performing writes over the whole
flash.

BUG=b:35104688
TESTED=Zaius flash is now written correctly for the 0xff regions.

Change-Id: I4c2fc769a8e0865edf8507f6bd796dc3344b4226
Signed-off-by: William A. Kennington III 
Reviewed-on: https://chromium-review.googlesource.com/472128
Commit-Ready: William Kennington 
Tested-by: William Kennington 
Reviewed-by: Brian Norris 
---
M flash.h
M flashrom.c
M linux_mtd.c
3 files changed, 16 insertions(+), 5 deletions(-)

git pull ssh://review.coreboot.org:29418/flashrom refs/changes/11/22511/1

diff --git a/flash.h b/flash.h
index 62f2e34..d16751b 100644
--- a/flash.h
+++ b/flash.h
@@ -120,6 +120,7 @@
 #define FEATURE_OTP		(1 << 8)
 #define FEATURE_QPI		(1 << 9)
 #define FEATURE_4BA_SUPPORT	(1 << 10)
+#define FEATURE_NO_ERASE	(1 << 11)

enum test_state {
    OK = 0,
diff --git a/flashrom.c b/flashrom.c
index 6329041..d7cafc2 100644
--- a/flashrom.c
+++ b/flashrom.c
@@ -1779,7 +1779,8 @@
    ret = 1;
    bool skipped = true;
    uint8_t *const curcontents = info->curcontents + info->erase_start;
-	if (need_erase(curcontents, newcontents, erase_len, flashctx->chip->gran)) {
+	if (!(flashctx->chip->feature_bits & FEATURE_NO_ERASE) &&
+			need_erase(curcontents, newcontents, erase_len, flashctx->chip->gran)) {
    	if (erase_block(flashctx, info, erasefn))
    		goto _free_ret;
    	/* Erase was successful. Adjust curcontents. */
diff --git a/linux_mtd.c b/linux_mtd.c
index 99a7ec0..9320bd1 100644
--- a/linux_mtd.c
+++ b/linux_mtd.c
@@ -48,6 +48,8 @@

static int mtd_device_is_writeable;

+static int mtd_no_erase;
+
 /* Size info is presented in bytes in sysfs. */
 static unsigned long int mtd_total_size;
 static unsigned long int mtd_numeraseregions;
@@ -131,6 +133,9 @@
    	/* cache for later use by write function */
    	mtd_device_is_writeable = 1;
    }
+	if (tmp & MTD_NO_ERASE) {
+		mtd_no_erase = 1;
+	}

/* Device name */
    if (read_sysfs_string("name", mtd_device_name, sizeof(mtd_device_name)))
@@ -174,10 +179,8 @@
    flash->chip->tested.read = OK;
    flash->chip->tested.erase = OK;
    flash->chip->tested.write = OK;
-	flash->chip->total_size = mtd_total_size / 1024;	/* bytes -> kB */
-	flash->chip->block_erasers[0].eraseblocks[0].size = mtd_erasesize;
-	flash->chip->block_erasers[0].eraseblocks[0].count =
-				mtd_total_size / mtd_erasesize;
+	if (mtd_no_erase)
+		flash->chip->feature_bits |= FEATURE_NO_ERASE;
 #if 0
    flash->chip->wp = &wp_mtd;
 #endif
@@ -255,6 +258,12 @@
 {
    uint32_t u;

+	if (mtd_no_erase) {
+		msg_perr("%s: device does not support erasing. Please file a "
+				"bug report at [e-mail]\n", __func__);
+		return 1;
+	}
+
    if (mtd_numeraseregions != 0) {
    	/* TODO: Support non-uniform eraseblock size using
    	   use MEMGETREGIONCOUNT/MEMGETREGIONINFO ioctls */