Mapping between bootpart taken from EXT_CSD_EXTRACT_BOOT_PART() and Partition Access bits used by the mmc_switch_part() function may be quite misleading. So add extended comment describing why in sunxi case is this mapping just a simple identity. Because in generic case this mapping requires non-trivial mapping table.
Signed-off-by: Pali Rohár pali@kernel.org --- arch/arm/mach-sunxi/board.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)
diff --git a/arch/arm/mach-sunxi/board.c b/arch/arm/mach-sunxi/board.c index 391a65a5495f..73519f6262ec 100644 --- a/arch/arm/mach-sunxi/board.c +++ b/arch/arm/mach-sunxi/board.c @@ -381,7 +381,17 @@ static bool sunxi_valid_emmc_boot(struct mmc *mmc) (mmc->ext_csd[EXT_CSD_BOOT_BUS_WIDTH] & 0x1b) != 0x09) return false;
- /* Partition 0 is the user data partition, bootpart must be 1 or 2. */ + /* + * bootpart == 0 means that eMMC booting is disabled. + * bootpart == 1 or 2 means to boot from Boot Partition 1 or 2. + * bootpart == 7 means to boot from User Area. + * Other bootpart values are reserved. + * mmc_switch_part() takes partition access value which is: + * 0 for User Area; 1-2 for Boot Partition 1-2; 3 for RPMB; 4-7 for GP 1-4. + * We allow booting only from Boot Partition 1 or 2 so + * bootpart mapping between EXT_CSD_EXTRACT_BOOT_PART() + * and mmc_switch_part() is straightforward identity. + */ if (bootpart != 1 && bootpart != 2) return false;