env_mmc: allow negative CONFIG_ENV_OFFSET

A negative value of CONFIG_ENV_OFFSET is treated as a backwards offset from the end of the eMMC device/partition, rather than a forwards offset from the start. This is useful when a single board may be stuffed with different eMMC devices, each of which has a different capacity, and you always want the environment to be stored at the very end of the device (or eMMC boot partition for example). One example of this case is NVIDIA's Ventana reference board. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Andy Fleming <afleming@freescale.com>

env_mmc: allow negative CONFIG_ENV_OFFSET
A negative value of CONFIG_ENV_OFFSET is treated as a backwards offset from the end of the eMMC device/partition, rather than a forwards offset from the start. This is useful when a single board may be stuffed with different eMMC devices, each of which has a different capacity, and you always want the environment to be stored at the very end of the device (or eMMC boot partition for example). One example of this case is NVIDIA's Ventana reference board. Signed-off-by: Stephen Warren <swarren@nvidia.com> Signed-off-by: Andy Fleming <afleming@freescale.com>
Stephen Warren · Andy Fleming · Eric Lee · Eric Lee · Eric Lee · Eric Lee
1 parent f866a46d6e
Showing 2 changed files with 21 additions and 2 deletions Side-by-side Diff
README
common/env_mmc.c
@@ -3666,6 +3666,14 @@
 	  These two #defines specify the offset and size of the environment
 	  area within the specified MMC device.
  
+	  If offset is positive (the usual case), it is treated as relative to
+	  the start of the MMC partition. If offset is negative, it is treated
+	  as relative to the end of the MMC partition. This can be useful if
+	  your board may be fitted with different MMC devices, which have
+	  different sizes for the MMC partitions, and you always want the
+	  environment placed at the very end of the partition, to leave the
+	  maximum possible space before it, to store other data.
+
 	  These two values are in units of bytes, but must be aligned to an
 	  MMC sector boundary.
  
@@ -3675,6 +3683,9 @@
 	  hold a redundant copy of the environment data. This provides a
 	  valid backup copy in case the other copy is corrupted, e.g. due
 	  to a power failure during a "saveenv" operation.
+
+	  This value may also be positive or negative; this is handled in the
+	  same way as CONFIG_ENV_OFFSET.
  
 	  This value is also in units of bytes, but must also be aligned to
 	  an MMC sector boundary.
@@ -53,11 +53,19 @@
  
 __weak int mmc_get_env_addr(struct mmc *mmc, int copy, u32 *env_addr)
 {
-	*env_addr = CONFIG_ENV_OFFSET;
+	s64 offset;
+
+	offset = CONFIG_ENV_OFFSET;
 #ifdef CONFIG_ENV_OFFSET_REDUND
 	if (copy)
-		*env_addr = CONFIG_ENV_OFFSET_REDUND;
+		offset = CONFIG_ENV_OFFSET_REDUND;
 #endif
+
+	if (offset < 0)
+		offset += mmc->capacity;
+
+	*env_addr = offset;
+
 	return 0;
 }
...	...	@@ -3666,6 +3666,14 @@
3666	3666	These two #defines specify the offset and size of the environment
3667	3667	area within the specified MMC device.
3668	3668
	3669	+ If offset is positive (the usual case), it is treated as relative to
	3670	+ the start of the MMC partition. If offset is negative, it is treated
	3671	+ as relative to the end of the MMC partition. This can be useful if
	3672	+ your board may be fitted with different MMC devices, which have
	3673	+ different sizes for the MMC partitions, and you always want the
	3674	+ environment placed at the very end of the partition, to leave the
	3675	+ maximum possible space before it, to store other data.
	3676	+
3669	3677	These two values are in units of bytes, but must be aligned to an
3670	3678	MMC sector boundary.
3671	3679
...	...	@@ -3675,6 +3683,9 @@
3675	3683	hold a redundant copy of the environment data. This provides a
3676	3684	valid backup copy in case the other copy is corrupted, e.g. due
3677	3685	to a power failure during a "saveenv" operation.
	3686	+
	3687	+ This value may also be positive or negative; this is handled in the
	3688	+ same way as CONFIG_ENV_OFFSET.
3678	3689
3679	3690	This value is also in units of bytes, but must also be aligned to
3680	3691	an MMC sector boundary.
...	...	@@ -53,11 +53,19 @@
53	53
54	54	__weak int mmc_get_env_addr(struct mmc mmc, int copy, u32 env_addr)
55	55	{
56		- *env_addr = CONFIG_ENV_OFFSET;
	56	+ s64 offset;
	57	+
	58	+ offset = CONFIG_ENV_OFFSET;
57	59	#ifdef CONFIG_ENV_OFFSET_REDUND
58	60	if (copy)
59		- *env_addr = CONFIG_ENV_OFFSET_REDUND;
	61	+ offset = CONFIG_ENV_OFFSET_REDUND;
60	62	#endif
	63	+
	64	+ if (offset < 0)
	65	+ offset += mmc->capacity;
	66	+
	67	+ *env_addr = offset;
	68	+
61	69	return 0;
62	70	}
63	71