rockchip: board: Increase rng-seed size to make it sufficient for modern Linux
Increase rng-seed size to make Linux happy and initialize rng pool instantly.
Linux 5.19+ requires 32 bytes of entropy to initialize random pool, but u-boot
currently provides only 8 bytes.
Linux 5.18 and probably some versions before it used to require 64 bytes.
Bump min value to 64 bytes to be on a safe side.
Boot with 8 byte rng-seed (Linux 6.11):
# dmesg | grep crng
[ 12.089286] random: crng init done
Boot with 32 byte rng-seed (Linux 6.11):
# dmesg | grep crng
[ 0.000000] random: crng init done
Linux source references:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c?h=v5.19#n551
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/char/random.c?h=v5.18#n236
Signed-off-by: Alex Shumsky <alexthreed@gmail.com>
Fixes: d2048bafae40 ("rockchip: board: Add board_rng_seed() for all Rockchip devices")
Reviewed-by: Dragan Simic <dsimic@manjaro.org>
Reviewed-by: Marek Vasut <marex@denx.de>
Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/include/fdt_support.h b/include/fdt_support.h
index 741e236..9447a64 100644
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -202,7 +202,8 @@
*
* This function is called if CONFIG_BOARD_RNG_SEED is set, and must
* be provided by the board. It should return, via @buf, some suitable
- * seed value to pass to the kernel.
+ * seed value to pass to the kernel. Seed size could be set in a decimal
+ * environment variable rng_seed_size and it defaults to 64 bytes.
*
* @param buf A struct abuf for returning the seed and its size.
* @return 0 if ok, negative on error.