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/configs/turris_omnia_defconfig b/configs/turris_omnia_defconfig
index 0df0f3c90b1232f46d25162b15e028fe9e8d57f1..4c21635ec90594f54ae52c3799c74c42ace2ada0 100644 (file)
--- a/configs/turris_omnia_defconfig
+++ b/configs/turris_omnia_defconfig
@@ -107,6 +107,7 @@ CONFIG_NVME_PCI=y
 CONFIG_PCI_MVEBU=y
 CONFIG_PINCTRL=y
 CONFIG_PINCTRL_ARMADA_38X=y
+CONFIG_DM_RNG=y
 CONFIG_DM_RTC=y
 CONFIG_RTC_ARMADA38X=y
 CONFIG_SERIAL_PROBE_ALL=y

diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig
index 041de538fac4b2371c50c359d2f8970bbc3babf9..6b06888454f41df4a715575fa457d87386d2c681 100644 (file)
--- a/drivers/misc/Kconfig
+++ b/drivers/misc/Kconfig
@@ -509,6 +509,7 @@ config TURRIS_OMNIA_MCU
        bool "Enable Turris Omnia MCU driver"
        depends on DM_I2C
        depends on DM_GPIO
+       depends on DM_RNG
        depends on SYSRESET
        default y if TARGET_TURRIS_OMNIA
        help

diff --git a/drivers/misc/turris_omnia_mcu.c b/drivers/misc/turris_omnia_mcu.c
index 77a0424d61cc60dc64937e3e5a496ebee089d829..6b2f17c0002d89893f1cb5e483d2535d1b8415c4 100644 (file)
--- 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 @@ U_BOOT_DRIVER(turris_omnia_mcu_sysreset) = {
        .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 @@ static int turris_omnia_mcu_probe(struct udevice *dev)
                        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;
 }