misc: turris_omnia_mcu: Add support for rng provided by MCU
Add support for true random number generator provided by the MCU on
Turris Omnia. The MCU firmware supports TRNG if the FEAT_TRNG bit is set
in features. In that case we bind the rng driver.
Signed-off-by: Marek Behún <kabel@kernel.org>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/misc/turris_omnia_mcu.c b/drivers/misc/turris_omnia_mcu.c
index 77a0424..6b2f17c 100644
--- a/drivers/misc/turris_omnia_mcu.c
+++ b/drivers/misc/turris_omnia_mcu.c
@@ -5,15 +5,20 @@
*/
#include <common.h>
+#include <console.h>
#include <dm.h>
#include <dm/lists.h>
#include <i2c.h>
+#include <rng.h>
#include <sysreset.h>
#include <turris-omnia-mcu-interface.h>
#include <asm/byteorder.h>
#include <asm/gpio.h>
+#include <linux/delay.h>
#include <linux/log2.h>
+#define CMD_TRNG_MAX_ENTROPY_LEN 64
+
struct turris_omnia_mcu_info {
u32 features;
};
@@ -282,6 +287,49 @@
.ops = &omnia_sysreset_ops,
};
+static int omnia_rng_read(struct udevice *dev, void *data, size_t count)
+{
+ u8 buf[1 + CMD_TRNG_MAX_ENTROPY_LEN];
+ size_t len;
+ int ret;
+
+ while (count) {
+ ret = dm_i2c_read(dev->parent, CMD_TRNG_COLLECT_ENTROPY, buf,
+ sizeof(buf));
+ if (ret)
+ return ret;
+
+ len = min_t(size_t, buf[0],
+ min_t(size_t, CMD_TRNG_MAX_ENTROPY_LEN, count));
+
+ if (!len) {
+ /* wait 500ms (fail if interrupted), then try again */
+ for (int i = 0; i < 5; ++i) {
+ mdelay(100);
+ if (ctrlc())
+ return -EINTR;
+ }
+ continue;
+ }
+
+ memcpy(data, &buf[1], len);
+ data += len;
+ count -= len;
+ }
+
+ return 0;
+}
+
+static const struct dm_rng_ops omnia_rng_ops = {
+ .read = omnia_rng_read,
+};
+
+U_BOOT_DRIVER(turris_omnia_mcu_trng) = {
+ .name = "turris-omnia-mcu-trng",
+ .id = UCLASS_RNG,
+ .ops = &omnia_rng_ops,
+};
+
static int turris_omnia_mcu_bind(struct udevice *dev)
{
/* bind MCU GPIOs as a child device */
@@ -336,6 +384,15 @@
return ret;
}
+ /* bind rng if trng is supported */
+ if (info->features & FEAT_TRNG) {
+ ret = device_bind_driver_to_node(dev, "turris-omnia-mcu-trng",
+ "turris-omnia-mcu-trng",
+ dev_ofnode(dev), NULL);
+ if (ret < 0)
+ return ret;
+ }
+
return 0;
}