[RFC PATCH v2 4/8] FWU: STM32MP1: Add support to read boot index from backup register

[Sughosh Ganu]

The FWU Multi Bank Update feature allows the platform to boot the
firmware images from one of the partitions(banks). The first stage
bootloader(fsbl) passes the value of the boot index, i.e. the bank
from which the firmware images were booted from to U-Boot. On the
STM32MP157C-DK2 board, this value is passed through one of the SoC's
backup register. Add a function to read the boot index value from the
backup register.

Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org>
---
Changes since V1:
* Use the TAMP_BOOTCOUNT register as suggested by Yann
  Gautier instead of the earlier unused register 10

 board/st/stm32mp1/stm32mp1.c | 7 +++++++
 include/fwu.h                | 1 +
 2 files changed, 8 insertions(+)

diff --git a/board/st/stm32mp1/stm32mp1.c b/board/st/stm32mp1/stm32mp1.c
index 28402fd127..a8543c6410 100644
--- a/board/st/stm32mp1/stm32mp1.c
+++ b/board/st/stm32mp1/stm32mp1.c
@@ -1090,6 +1090,13 @@ int fwu_plat_get_blk_desc(struct blk_desc **desc)
 	return 0;
 }
 
+void fwu_plat_get_bootidx(void *boot_idx)
+{
+	u32 *bootidx = boot_idx;
+
+	*bootidx = readl(TAMP_BOOTCOUNT);
+}
+
 struct fwu_mdata_ops *get_plat_fwu_mdata_ops(void)
 {
 	if (CONFIG_IS_ENABLED(TARGET_ST_STM32MP15x) &&
diff --git a/include/fwu.h b/include/fwu.h
index 1e7a1eabff..5ba437798d 100644
--- a/include/fwu.h
+++ b/include/fwu.h
@@ -29,5 +29,6 @@ int fwu_plat_get_update_index(u32 *update_idx);
 int fwu_plat_get_blk_desc(struct blk_desc **desc);
 int fwu_plat_get_alt_num(int dev_num, void *identifier);
 int fwu_plat_fill_partition_guids(efi_guid_t **part_guid_arr);
+void fwu_plat_get_bootidx(void *boot_idx);
 
 #endif /* _FWU_H_ */
-- 
2.17.1