drivers: entropy: esp32: update register call

Update entropy driver to use proper registers

Signed-off-by: Sylvio Alves <sylvio.alves@espressif.com>

drivers/clock_control/clock_control_esp32.c

@@ -20,6 +20,7 @@
 #include <drivers/clock_control.h>
 #include <sys/util.h>
 #include "clock_control_esp32.h"
+#include "driver/periph_ctrl.h"
 
 struct esp32_clock_config {
 	uint32_t clk_src_sel;
@@ -176,6 +177,16 @@ static inline uint32_t clk_val_to_reg_val(uint32_t val)
 	return (val & UINT16_MAX) | ((val & UINT16_MAX) << 16);
 }
 
+int IRAM_ATTR esp_clk_cpu_freq(void)
+{
+	return MHZ(esp32_rom_g_ticks_per_us_pro);
+}
+
+int IRAM_ATTR esp_clk_apb_freq(void)
+{
+	return MHZ(MIN(esp32_rom_g_ticks_per_us_pro, 80));
+}
+
 void IRAM_ATTR ets_update_cpu_frequency(uint32_t ticks_per_us)
 {
 	/* Update scale factors used by ets_delay_us */
@@ -326,6 +337,9 @@ static int clock_control_esp32_init(const struct device *dev)
 		return -EINVAL;
 	}
 
+	/* Enable RNG clock. */
+	periph_module_enable(PERIPH_RNG_MODULE);
+
 	/* Re-calculate the CCOUNT register value to make time calculation correct.
 	 * This should be updated on each frequency change
 	 * New CCOUNT = Current CCOUNT * (new freq / old freq)

drivers/clock_control/clock_control_esp32.h

@@ -18,15 +18,6 @@
 #define I2C_READREG_RTC(block, reg_add)	\
 	esp32_rom_i2c_readReg(block, block##_HOSTID,  reg_add)
 
-
-# define XTHAL_GET_CCOUNT()     ({ int __ccount;					     \
-				   __asm__ __volatile__ ("rsr.ccount %0" : "=a" (__ccount)); \
-				   __ccount; })
-
-# define XTHAL_SET_CCOUNT(v)    do { int __ccount = (int)(v);						   \
-				     __asm__ __volatile__ ("wsr.ccount %0" : : "a" (__ccount) : "memory"); \
-				} while (0)
-
 /*
  * Get voltage level for CPU to run at 240 MHz, or for flash/PSRAM to run at 80 MHz.
  * 0x0: level 7; 0x1: level 6; 0x2: level 5; 0x3: level 4. (RO)

drivers/entropy/Kconfig.esp32

@@ -7,6 +7,7 @@ config ENTROPY_ESP32_RNG
 	bool "ESP32 entropy number generator driver"
 	depends on SOC_ESP32
 	select ENTROPY_HAS_DRIVER
+	default y
 	help
 	  This option enables the entropy number generator for ESP32 SoCs.
 

drivers/entropy/entropy_esp32.c

@@ -8,41 +8,53 @@
 
 #include <string.h>
 #include <drivers/entropy.h>
+#include <soc/dport_reg.h>
+#include <soc/rtc.h>
+#include <soc/wdev_reg.h>
+#include <soc/rtc_cntl_reg.h>
+#include <soc/apb_ctrl_reg.h>
+#include <esp_system.h>
+#include <soc.h>
+
+extern int esp_clk_cpu_freq(void);
+extern int esp_clk_apb_freq(void);
 
 static inline uint32_t entropy_esp32_get_u32(void)
 {
-	/*
-	 * APB Address:   0x60035144 (Safe,slower writes)
-	 * DPORT Address: 0x3ff75144 (write bug, fast writes)
-	 * In this case it won't make a difference because it is read only
-	 * More info available at:
-	 * https://www.esp32.com/viewtopic.php?f=2&t=3033&p=14227
-	 * also check: ECO and Workarounds for Bugs Document, point 3.3
+	/* The PRNG which implements WDEV_RANDOM register gets 2 bits
+	 * of extra entropy from a hardware randomness source every APB clock cycle
+	 * (provided WiFi or BT are enabled). To make sure entropy is not drained
+	 * faster than it is added, this function needs to wait for at least 16 APB
+	 * clock cycles after reading previous word. This implementation may actually
+	 * wait a bit longer due to extra time spent in arithmetic and branch statements.
 	 */
-	volatile uint32_t *rng_data_reg = (uint32_t *)DT_INST_REG_ADDR(0);
 
-	/* Read just once.  This is not optimal as the generator has
-	 * limited throughput due to scarce sources of entropy, specially
-	 * with the radios turned off.  Might want to revisit this.
-	 */
-	return *rng_data_reg;
+	uint32_t cpu_to_apb_freq_ratio =
+		esp_clk_cpu_freq() / esp_clk_apb_freq();
+
+	static uint32_t last_ccount;
+	uint32_t ccount;
+
+	do {
+		ccount = XTHAL_GET_CCOUNT();
+	} while (ccount - last_ccount < cpu_to_apb_freq_ratio * 16);
+	last_ccount = ccount;
+	return REG_READ(WDEV_RND_REG);
 }
 
-static int entropy_esp32_get_entropy(const struct device *device,
-				     uint8_t *buf, uint16_t len)
+static int entropy_esp32_get_entropy(const struct device *device, uint8_t *buf,
+				     uint16_t len)
 {
-	while (len) {
-		uint32_t v = entropy_esp32_get_u32();
+	assert(buf != NULL);
+	uint8_t *buf_bytes = (uint8_t *)buf;
 
-		if (len >= sizeof(v)) {
-			memcpy(buf, &v, sizeof(v));
+	while (len > 0) {
+		uint32_t word = entropy_esp32_get_u32();
+		uint32_t to_copy = MIN(sizeof(word), len);
 
-			buf += sizeof(v);
-			len -= sizeof(v);
-		} else {
-			memcpy(buf, &v, len);
-			break;
-		}
+		memcpy(buf_bytes, &word, to_copy);
+		buf_bytes += to_copy;
+		len -= to_copy;
 	}
 
 	return 0;
@@ -50,10 +62,11 @@ static int entropy_esp32_get_entropy(const struct device *device,
 
 static int entropy_esp32_init(const struct device *device)
 {
+	/* clock initialization handled by clock manager */
 	return 0;
 }
 
-static struct entropy_driver_api entropy_esp32_api_funcs = {
+static const struct entropy_driver_api entropy_esp32_api_funcs = {
 	.get_entropy = entropy_esp32_get_entropy
 };
 

include/arch/xtensa/xtensa_api.h

@@ -7,6 +7,7 @@
 #define ZEPHYR_ARCH_XTENSA_INCLUDE_XTENSA_API_H_
 
 #include <xtensa/hal.h>
+#include <xtensa/core-macros.h>
 #include "xtensa_rtos.h"
 #include "xtensa_context.h"