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/arch/arm/mach-rockchip/board.c b/arch/arm/mach-rockchip/board.c
index 3fadf7e412228c7c6ad5ac9444e8c33e494e5fcd..75d6693e28a481c0d1385cc12a0d73d308f0a41b 100644 (file)
--- a/arch/arm/mach-rockchip/board.c
+++ b/arch/arm/mach-rockchip/board.c
@@ -472,9 +472,18 @@ __weak int misc_init_r(void)
 __weak int board_rng_seed(struct abuf *buf)
 {
        struct udevice *dev;
-       size_t len = 0x8;
+       ulong len = env_get_ulong("rng_seed_size", 10, 64);
        u64 *data;
 
+       if (len < 64) {
+               /*
+                * rng_seed_size should be at least 32 bytes for Linux 5.19+,
+                * or 64 for older Linux kernel versions
+                */
+               log_warning("Value for rng_seed_size (%lu) too low, Linux kernel RNG may fail to initialize early\n",
+                           len);
+       }
+
        data = malloc(len);
        if (!data) {
                printf("Out of memory\n");

diff --git a/common/Kconfig b/common/Kconfig
index 90cee19d41340c018ca359301305878ded9609bf..14a6c44c8047b4299770d2f60038f3220bf27f53 100644 (file)
--- a/common/Kconfig
+++ b/common/Kconfig
@@ -928,6 +928,9 @@ config BOARD_RNG_SEED
          new seed for use on subsequent boots, and whether or not the
          kernel should account any entropy from the given seed.
 
+         Default seed size (64 bytes) can be overridden by a decimal
+         environment variable rng_seed_size.
+
 endmenu
 
 menu "Update support"

diff --git a/doc/usage/environment.rst b/doc/usage/environment.rst
index cc33d3ec0f2f915cd333331db258a4249b7c0f75..7bd9ffce8d8c4d1c9365b41395dd4b8536008011 100644 (file)
--- a/doc/usage/environment.rst
+++ b/doc/usage/environment.rst
@@ -323,6 +323,11 @@ netretry
     Useful on scripts which control the retry operation
     themselves.
 
+rng_seed_size
+    Size of random value added to device-tree node /chosen/rng-seed.
+    This variable is given as a decimal number.
+    If unset, 64 bytes is used as the default.
+
 silent_linux
     If set then Linux will be told to boot silently, by
     adding 'console=' to its command line. If "yes" it will be

diff --git a/include/fdt_support.h b/include/fdt_support.h
index 741e2360c224c61e34af4c7cead7b60063d3ef1a..9447a64e060da4c4f6e1c1b509dd477c29e040f4 100644 (file)
--- a/include/fdt_support.h
+++ b/include/fdt_support.h
@@ -202,7 +202,8 @@ int ft_board_setup(void *blob, struct bd_info *bd);
  *
  * 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.