drivers: add CC13xx / CC26xx entropy driver

Add driver for the TRNG entropy source on the TI CC13xx / CC26xx
series SoCs.

Signed-off-by: Brett Witherspoon <spoonb@cdspooner.com>

drivers/entropy/CMakeLists.txt

@@ -2,6 +2,7 @@
 
 zephyr_library()
 
+zephyr_library_sources_ifdef(CONFIG_ENTROPY_CC13XX_CC26XX_RNG  entropy_cc13xx_cc26xx.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_ESP32_RNG          entropy_esp32.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_RNGA          entropy_mcux_rnga.c)
 zephyr_library_sources_ifdef(CONFIG_ENTROPY_MCUX_TRNG          entropy_mcux_trng.c)

drivers/entropy/Kconfig

@@ -13,6 +13,7 @@ menuconfig ENTROPY_GENERATOR
 
 if ENTROPY_GENERATOR
 
+source "drivers/entropy/Kconfig.cc13xx_cc26xx"
 source "drivers/entropy/Kconfig.mcux"
 source "drivers/entropy/Kconfig.stm32"
 source "drivers/entropy/Kconfig.esp32"

drivers/entropy/Kconfig.cc13xx_cc26xx

@@ -0,0 +1,51 @@
+# Kconfig.cc13xx_cc26xx - TI CC13xx / CC26xx entropy driver configuration
+#
+# Copyright (c) 2019 Brett Witherspoon
+#
+# SPDX-License-Identifier: Apache-2.0
+
+config ENTROPY_CC13XX_CC26XX_RNG
+	bool "TI SimpleLink CC13xx / CC26xx True Random Number Generator (TRNG)"
+	depends on SOC_SERIES_CC13X2_CC26X2
+	select ENTROPY_HAS_DRIVER
+	select HAS_DTS_ENTROPY
+	select RING_BUFFER
+	help
+	  This option enables the driver for the True Random Number Generator (TRNG)
+	  for TI SimpleLink CC13xx / CC26xx SoCs.
+
+if ENTROPY_CC13XX_CC26XX_RNG
+
+config ENTROPY_CC13XX_CC26XX_POOL_SIZE
+	int "Number of bytes in the entropy pool"
+	default 512
+	help
+	  The size in bytes of the buffer used to store entropy generated by the
+	  hardware. Should be a power of two for high performance.
+
+config ENTROPY_CC13XX_CC26XX_SAMPLES_PER_CYCLE
+	int "Number of samples to generate entropy"
+	range 256 16777216
+	default 240000
+	help
+	  The number of samples used to generate entropy. The time required to
+	  generate 64 bits of entropy is determined by the number of FROs enabled,
+	  the sampling (system) clock frequency, and this value.
+
+config ENTROPY_CC13XX_CC26XX_ALARM_THRESHOLD
+	int "Threshold for detected repeated patterns"
+	range 0 255
+	default 255
+	help
+	  The number of samples detected with repeating patterns before an alarm
+	  event is triggered. The associated FRO is automatically shut down.
+
+config ENTROPY_CC13XX_CC26XX_SHUTDOWN_THRESHOLD
+	int "Threshold for the number of FROs automatically shut down"
+	range 0 24
+	default 0
+	help
+	  The number of FROs allowed to be shutdown before the driver attempts to
+	  take corrective action.
+
+endif # ENTROPY_CC13XX_CC26XX_RNG

drivers/entropy/entropy_cc13xx_cc26xx.c

@@ -0,0 +1,170 @@
+/*
+ * Copyright (c) 2019 Brett Witherspoon
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <kernel.h>
+#include <device.h>
+#include <entropy.h>
+#include <irq.h>
+#include <ring_buffer.h>
+#include <sys_io.h>
+
+#include <driverlib/prcm.h>
+#include <driverlib/trng.h>
+
+struct entropy_cc13xx_cc26xx_data {
+	struct k_sem lock;
+	struct k_sem sync;
+	struct ring_buf pool;
+	u8_t data[CONFIG_ENTROPY_CC13XX_CC26XX_POOL_SIZE];
+};
+
+DEVICE_DECLARE(entropy_cc13xx_cc26xx);
+
+static inline struct entropy_cc13xx_cc26xx_data *
+get_dev_data(struct device *dev)
+{
+	return dev->driver_data;
+}
+
+static int entropy_cc13xx_cc26xx_get_entropy(struct device *dev, u8_t *buf,
+					     u16_t len)
+{
+	struct entropy_cc13xx_cc26xx_data *data = get_dev_data(dev);
+	u32_t cnt;
+
+	TRNGIntEnable(TRNG_NUMBER_READY);
+
+	while (len) {
+		k_sem_take(&data->lock, K_FOREVER);
+		cnt = ring_buf_get(&data->pool, buf, len);
+		k_sem_give(&data->lock);
+
+		if (cnt) {
+			buf += cnt;
+			len -= cnt;
+		} else {
+			k_sem_take(&data->sync, K_FOREVER);
+		}
+	}
+
+	return 0;
+}
+
+static void entropy_cc13xx_cc26xx_isr(void *arg)
+{
+	struct entropy_cc13xx_cc26xx_data *data = get_dev_data(arg);
+	u32_t src, cnt, off;
+	u32_t num[2];
+
+	/* Interrupt service routine as described in TRM section 18.6.1.3.2 */
+	src = TRNGStatusGet();
+
+	if (src & TRNG_NUMBER_READY) {
+		/* This function acknowledges the ready status */
+		num[1] = TRNGNumberGet(TRNG_HI_WORD);
+		num[0] = TRNGNumberGet(TRNG_LOW_WORD);
+
+		cnt = ring_buf_put(&data->pool, (u8_t *)num, sizeof(num));
+
+		/* When pool is full disable interrupt and stop reading numbers */
+		if (cnt != sizeof(num)) {
+			TRNGIntDisable(TRNG_NUMBER_READY);
+		}
+
+		k_sem_give(&data->sync);
+	}
+
+	/* Change the shutdown FROs' oscillating frequncy in an attempt to
+	 * prevent further locking on to the sampling clock frequncy.
+	 */
+	if (src & TRNG_FRO_SHUTDOWN) {
+		/* Clear shutdown */
+		TRNGIntClear(TRNG_FRO_SHUTDOWN);
+		/* Disabled FROs */
+		off = sys_read32(TRNG_BASE + TRNG_O_ALARMSTOP);
+		/* Clear alarms */
+		sys_write32(0, TRNG_BASE + TRNG_O_ALARMMASK);
+		sys_write32(0, TRNG_BASE + TRNG_O_ALARMSTOP);
+		/* De-tune FROs */
+		sys_write32(off, TRNG_BASE + TRNG_O_FRODETUNE);
+		/* Re-enable FROs */
+		sys_write32(off, TRNG_BASE + TRNG_O_FROEN);
+	}
+}
+
+static int entropy_cc13xx_cc26xx_init(struct device *dev)
+{
+	struct entropy_cc13xx_cc26xx_data *data = get_dev_data(dev);
+
+	/* Power TRNG domain */
+	PRCMPowerDomainOn(PRCM_DOMAIN_PERIPH);
+
+	/* Enable TRNG peripheral clocks */
+	PRCMPeripheralRunEnable(PRCM_PERIPH_TRNG);
+	/* Enabled the TRNG while in sleep mode to keep the entropy pool full. After
+	 * the pool is full the TRNG will enter idle mode when random numbers are no
+	 * longer being read. */
+	PRCMPeripheralSleepEnable(PRCM_PERIPH_TRNG);
+	PRCMPeripheralDeepSleepEnable(PRCM_PERIPH_TRNG);
+
+
+	/* Load PRCM settings */
+	PRCMLoadSet();
+	while (!PRCMLoadGet()) {
+		continue;
+	}
+
+	/* Peripherals should not be accessed until power domain is on. */
+	while (PRCMPowerDomainStatus(PRCM_DOMAIN_PERIPH) !=
+	       PRCM_DOMAIN_POWER_ON) {
+		continue;
+	}
+
+	/* Initialize driver data */
+	ring_buf_init(&data->pool, sizeof(data->data), data->data);
+
+	/* Initialization as described in TRM section 18.6.1.2 */
+	TRNGReset();
+	while (sys_read32(TRNG_BASE + TRNG_O_SWRESET)) {
+		continue;
+	}
+
+	/* Set samples per cycle */
+	TRNGConfigure(0, CONFIG_ENTROPY_CC13XX_CC26XX_SAMPLES_PER_CYCLE, 0);
+	/* De-tune FROs */
+	sys_write32(TRNG_FRODETUNE_FRO_MASK_M, TRNG_BASE + TRNG_O_FRODETUNE);
+	/* Enable FROs */
+	sys_write32(TRNG_FROEN_FRO_MASK_M, TRNG_BASE + TRNG_O_FROEN);
+	/* Set shutdown and alarm thresholds */
+	sys_write32((CONFIG_ENTROPY_CC13XX_CC26XX_SHUTDOWN_THRESHOLD << 16) |
+			    CONFIG_ENTROPY_CC13XX_CC26XX_ALARM_THRESHOLD,
+		    TRNG_BASE + TRNG_O_ALARMCNT);
+
+	TRNGEnable();
+	TRNGIntEnable(TRNG_NUMBER_READY | TRNG_FRO_SHUTDOWN);
+
+	IRQ_CONNECT(DT_TI_CC13XX_CC26XX_TRNG_0_IRQ_0,
+		    DT_TI_CC13XX_CC26XX_TRNG_0_IRQ_0_PRIORITY,
+		    entropy_cc13xx_cc26xx_isr,
+		    DEVICE_GET(entropy_cc13xx_cc26xx), 0);
+	irq_enable(DT_TI_CC13XX_CC26XX_TRNG_0_IRQ_0);
+
+	return 0;
+}
+
+static const struct entropy_driver_api entropy_cc13xx_cc26xx_driver_api = {
+	.get_entropy = entropy_cc13xx_cc26xx_get_entropy,
+};
+
+static struct entropy_cc13xx_cc26xx_data entropy_cc13xx_cc26xx_data = {
+	.lock = Z_SEM_INITIALIZER(entropy_cc13xx_cc26xx_data.lock, 1, 1),
+	.sync = Z_SEM_INITIALIZER(entropy_cc13xx_cc26xx_data.sync, 0, 1),
+};
+
+DEVICE_AND_API_INIT(entropy_cc13xx_cc26xx, DT_TI_CC13XX_CC26XX_TRNG_0_LABEL,
+		    entropy_cc13xx_cc26xx_init, &entropy_cc13xx_cc26xx_data,
+		    NULL, PRE_KERNEL_1, CONFIG_KERNEL_INIT_PRIORITY_DEVICE,
+		    &entropy_cc13xx_cc26xx_driver_api);

dts/arm/ti/cc13x2_cc26x2.dtsi

@@ -52,6 +52,14 @@
 			#gpio-cells = <2>;
 		};
 
+		trng: random@40028000 {
+			compatible = "ti,cc13xx-cc26xx-trng";
+			reg = <0x40028000 0x2000>;
+			interrupts = <33 0>;
+			status = "disabled";
+			label = "TRNG";
+		};
+
 		uart0: uart@40001000 {
 			compatible = "ti,cc13xx-cc26xx-uart";
 			reg = <0x40001000 0x1000>;

dts/bindings/rng/ti,cc13xx-cc26xx-trng.yaml

@@ -0,0 +1,39 @@
+#
+# Copyright (c) 2019 Brett Witherspoon
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+---
+title: TI SimpleLink CC13xx / CC26xx True Random Number Generator (TRNG)
+version: 0.1
+
+description: >
+    This is a representation of the TI SimpleLink CC13xx / CC26xx TRNG node
+
+properties:
+    compatible:
+      type: string
+      category: required
+      description: compatible strings
+      constraint: "ti,cc13xx-cc26xx-trng"
+      generation: define
+
+    reg:
+      type: int
+      description: mmio register space
+      generation: define
+      category: required
+
+    interrupts:
+      type: compound
+      category: required
+      description: required interrupts
+      generation: define
+
+    label:
+      type: string
+      category: required
+      description: Human readable string describing the device (used by Zephyr for API name)
+      generation: define
+
+...

soc/arm/ti_simplelink/cc13x2_cc26x2/Kconfig.defconfig.series

@@ -39,6 +39,13 @@ config GPIO_CC13XX_CC26XX
 
 endif # GPIO
 
+if ENTROPY_GENERATOR
+
+config ENTROPY_CC13XX_CC26XX_RNG
+	default y
+
+endif # ENTROPY_GENERATOR
+
 if SERIAL
 
 config UART_CC13XX_CC26XX

soc/arm/ti_simplelink/cc13x2_cc26x2/dts_fixup.h

@@ -7,5 +7,6 @@
 /* SoC level DTS fixup file */
 
 #define DT_NUM_IRQ_PRIO_BITS DT_ARM_V7M_NVIC_E000E100_ARM_NUM_IRQ_PRIORITY_BITS
+#define CONFIG_ENTROPY_NAME DT_TI_CC13XX_CC26XX_TRNG_0_LABEL
 
 /* End of SoC Level DTS fixup file */