drivers: entropy: Add SAM0 entropy driver

CODEOWNERS

@@ -129,6 +129,7 @@
 /drivers/ps2/                             @albertofloyd @franciscomunoz @scottwcpg
 /drivers/kscan/                           @albertofloyd @franciscomunoz @scottwcpg
 /drivers/ethernet/                        @jukkar @tbursztyka @pfalcon
+/drivers/entropy/*sam0*                   @benpicco
 /drivers/flash/                           @nashif @nvlsianpu
 /drivers/flash/*native_posix*             @vanwinkeljan @aescolar
 /drivers/flash/*nrf*                      @nvlsianpu

drivers/entropy/CMakeLists.txt

@@ -8,6 +8,7 @@ zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_RNGA          entropy_mcux_rnga
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_TRNG          entropy_mcux_trng.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_NRF5_RNG           entropy_nrf5.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_SAM_RNG            entropy_sam.c)
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_SAM0_RNG           entropy_sam0.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_STM32_RNG          entropy_stm32.c)
 zephyr_library_sources_ifdef(CONFIG_FAKE_ENTROPY_NATIVE_POSIX  fake_entropy_native_posix.c)
 zephyr_library_sources_ifdef(CONFIG_USERSPACE                  entropy_handlers.c)

drivers/entropy/Kconfig

@@ -19,6 +19,7 @@ source "drivers/entropy/Kconfig.stm32"
 source "drivers/entropy/Kconfig.esp32"
 source "drivers/entropy/Kconfig.nrf5"
 source "drivers/entropy/Kconfig.sam"
+source "drivers/entropy/Kconfig.sam0"
 source "drivers/entropy/Kconfig.native_posix"
 
 config ENTROPY_HAS_DRIVER

drivers/entropy/Kconfig.sam0

@@ -0,0 +1,13 @@
+# Kconfig.sam - Atmel SAM0 TRNG configuration
+#
+# Copyright (c) 2019 Benjamin Valentin
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_SAM0_RNG
+	bool "Atmel SAM0 MCU Family True Random Number Generator (TRNG) Driver"
+	depends on SOC_FAMILY_SAM0
+	select ENTROPY_HAS_DRIVER
+	select HAS_DTS_ENTROPY
+	help
+	  Enable True Random Number Generator (TRNG) driver for Atmel SAM0 MCUs.

drivers/entropy/entropy_sam0.c

@@ -0,0 +1,159 @@
+/*
+ * Copyright (c) 2019 ML!PA Consulting GmbH
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <device.h>
+#include <drivers/entropy.h>
+#include <errno.h>
+#include <init.h>
+#include <soc.h>
+#include <string.h>
+
+struct trng_sam0_dev_cfg {
+	Trng *regs;
+};
+
+#define DEV_CFG(dev) \
+	((const struct trng_sam0_dev_cfg *const)(dev)->config->config_info)
+
+static int entropy_sam0_wait_ready(Trng *const trng, u32_t flags)
+{
+	/* According to the reference manual, the generator provides
+	 * one 32-bit random value every 84 peripheral clock cycles.
+	 * MCK may not be smaller than HCLK/4, so it should not take
+	 * more than 336 HCLK ticks. Assuming the CPU can do 1
+	 * instruction per HCLK the number of times to loop before
+	 * the TRNG is ready is less than 1000. And that is when
+	 * assuming the loop only takes 1 instruction. So looping a
+	 * million times should be more than enough.
+	 */
+	int timeout = 1000000;
+
+	while (!trng->INTFLAG.bit.DATARDY) {
+		if (timeout-- == 0) {
+			return -ETIMEDOUT;
+		}
+
+		if ((flags & ENTROPY_BUSYWAIT) == 0U) {
+			/* This internal function is used by both get_entropy,
+			 * and get_entropy_isr APIs. The later may call this
+			 * function with the ENTROPY_BUSYWAIT flag set. In
+			 * that case make no assumption that the kernel is
+			 * initialized when the function is called; so, just
+			 * do busy-wait for the random data to be ready.
+			 */
+			k_yield();
+		}
+	}
+
+	return 0;
+}
+
+static int entropy_sam0_get_entropy_internal(struct device *dev, u8_t *buffer,
+				   u16_t length, u32_t flags)
+{
+	Trng *const trng = DEV_CFG(dev)->regs;
+
+	while (length > 0) {
+		size_t to_copy;
+		u32_t value;
+		int res;
+
+		res = entropy_sam0_wait_ready(trng, flags);
+		if (res < 0) {
+			return res;
+		}
+
+		value = TRNG->DATA.reg;
+		to_copy = MIN(length, sizeof(value));
+
+		memcpy(buffer, &value, to_copy);
+		buffer += to_copy;
+		length -= to_copy;
+	}
+
+	return 0;
+}
+
+static int entropy_sam0_get_entropy(struct device *dev, u8_t *buffer,
+				   u16_t length)
+{
+	return entropy_sam0_get_entropy_internal(dev, buffer, length, 0);
+}
+
+static int entropy_sam0_get_entropy_isr(struct device *dev, u8_t *buffer,
+				   u16_t length, u32_t flags)
+{
+	u16_t cnt = length;
+
+
+	if ((flags & ENTROPY_BUSYWAIT) == 0U) {
+
+		/* No busy wait; return whatever data is available. */
+
+		Trng *const trng = DEV_CFG(dev)->regs;
+
+		do {
+			size_t to_copy;
+			u32_t value;
+
+			if (!(trng->INTFLAG.bit.DATARDY)) {
+
+				/* Data not ready */
+				break;
+			}
+
+			value = TRNG->DATA.reg;
+			to_copy = MIN(length, sizeof(value));
+
+			memcpy(buffer, &value, to_copy);
+			buffer += to_copy;
+			length -= to_copy;
+
+		} while (length > 0);
+
+		return cnt - length;
+
+	} else {
+		/* Allowed to busy-wait */
+		int ret =
+			entropy_sam0_get_entropy_internal(dev,
+				buffer, length, flags);
+
+		if (ret == 0) {
+			/* Data retrieved successfully. */
+			return cnt;
+		}
+
+		return ret;
+	}
+}
+
+static int entropy_sam0_init(struct device *dev)
+{
+	Trng *const trng = DEV_CFG(dev)->regs;
+
+	/* Enable the MCLK */
+	MCLK->APBCMASK.bit.TRNG_ = 1;
+
+	/* Enable the TRNG */
+	trng->CTRLA.bit.ENABLE = 1;
+
+	return 0;
+}
+
+static const struct entropy_driver_api entropy_sam0_api = {
+	.get_entropy = entropy_sam0_get_entropy,
+	.get_entropy_isr = entropy_sam0_get_entropy_isr
+};
+
+static const struct trng_sam0_dev_cfg trng_sam0_cfg = {
+	.regs = (Trng *)DT_ATMEL_SAM0_TRNG_0_BASE_ADDRESS,
+};
+
+DEVICE_AND_API_INIT(entropy_sam0, CONFIG_ENTROPY_NAME,
+		    entropy_sam0_init, NULL, &trng_sam0_cfg,
+		    PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
+		    &entropy_sam0_api);

dts/bindings/rng/atmel,sam0-trng.yaml

@@ -0,0 +1,21 @@
+# Copyright (c) 2019 ML!PA Consulting GmbH
+# SPDX-License-Identifier: Apache-2.0
+
+title: Atmel SAM0 TRNG (True Random Number Generator)
+
+description: >
+    This binding gives a base representation of the Atmel SAM0 RNG
+
+compatible: "atmel,sam0-trng"
+
+include: base.yaml
+
+properties:
+    reg:
+      required: true
+
+    interrupts:
+      required: true
+
+    label:
+      required: true