[RFC][PATCH] rpi: Fix DRAM size reporting to show total RAM

[Anders Roxell]

The VideoCore mailbox GET_ARM_MEMORY only reports the size of the
first accessible memory region (~947 MiB on RPi4 with 8GB), not the
total RAM. This causes U-Boot to display "DRAM: 947 MiB (total 7.9 GiB)"
instead of "DRAM: 7.9 GiB".

On Raspberry Pi 4 with 8GB RAM, the memory is split across multiple
non-contiguous banks. The dram_init() function only sets gd->ram_size
to the first bank size reported by the VideoCore firmware, while
fdtdec_setup_memory_banksize() correctly populates all memory banks
from the device tree.

Fix this by updating gd->ram_size after dram_init_banksize() has
populated all memory banks, so it reflects the actual total RAM
across all banks.

Signed-off-by: Anders Roxell <anders.roxell at linaro.org>
---
 board/raspberrypi/rpi/rpi.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c
index 1b0b664fa2b7..0cd45104b3bc 100644
--- a/board/raspberrypi/rpi/rpi.c
+++ b/board/raspberrypi/rpi/rpi.c
@@ -332,13 +332,27 @@ int dram_init(void)
 #ifdef CONFIG_OF_BOARD
 int dram_init_banksize(void)
 {
+	phys_addr_t total_size = 0;
+	int i;
 	int ret;
 
 	ret = fdtdec_setup_memory_banksize();
 	if (ret)
 		return ret;
 
-	return fdtdec_setup_mem_size_base();
+	ret = fdtdec_setup_mem_size_base();
+	if (ret)
+		return ret;
+
+	/* Update gd->ram_size to reflect total RAM across all banks */
+	for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
+		if (gd->bd->bi_dram[i].size == 0)
+			break;
+		total_size += gd->bd->bi_dram[i].size;
+	}
+	gd->ram_size = total_size;
+
+	return 0;
 }
 #endif
 
-- 
2.51.0