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env_mmc: allow negative CONFIG_ENV_OFFSET

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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>
This commit is contained in:
Stephen Warren 2013-06-11 15:14:02 -06:00 committed by Andy Fleming
parent f866a46d6e
commit 5c088ee841
2 changed files with 21 additions and 2 deletions
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11
README
View file

@ -3666,6 +3666,14 @@ but it can not erase, write this NOR flash by SRIO or PCIE interface.
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.
@ -3676,6 +3684,9 @@ but it can not erase, write this NOR flash by SRIO or PCIE interface.
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.

12
common/env_mmc.c
View file

@ -53,11 +53,19 @@ DECLARE_GLOBAL_DATA_PTR;
__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;
}