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drivers: entropy_mcux_caam: Add semaphore

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Add a semaphore to the entropy mcux caam driver
to make the driver thread safe, since some static
variables in the HAL can be the source of
some race conditions.

Signed-off-by: Declan Snyder <declan.snyder@nxp.com>
This commit is contained in:
Declan Snyder 2023-05-05 16:44:41 +00:00 • committed by David Leach
commit f4c2dc54b4
1 changed files with 14 additions and 0 deletions
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14
drivers/entropy/entropy_mcux_caam.c
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@ -10,6 +10,7 @@
#include <zephyr/drivers/entropy.h>
#include <zephyr/random/rand32.h>
#include <zephyr/init.h>
#include <zephyr/kernel.h>
#include "fsl_caam.h"
@ -21,6 +22,10 @@ static caam_job_ring_interface_t jrif0 __attribute__((__section__(".nocache")));
static uint8_t rng_buff_pool[CONFIG_ENTRY_MCUX_CAAM_POOL_SIZE]
__attribute__((__section__(".nocache")));
/* This semaphore is needed to prevent race condition to static variables in the HAL driver */
K_SEM_DEFINE(mcux_caam_sem, 1, 1)
static int entropy_mcux_caam_get_entropy(const struct device *dev,
uint8_t *buffer,
uint16_t length)
@ -30,6 +35,8 @@ static int entropy_mcux_caam_get_entropy(const struct device *dev,
caam_handle_t handle;
uint16_t read_length = 0;
uint16_t insert_idx = 0;
int ret = 0;
k_timeout_t sem_timeout = K_MSEC(10);
handle.jobRing = kCAAM_JobRing0;
@ -41,10 +48,17 @@ static int entropy_mcux_caam_get_entropy(const struct device *dev,
while (insert_idx < length) {
read_length = MIN(sizeof(rng_buff_pool), (length - insert_idx));
ret = k_sem_take(&mcux_caam_sem, sem_timeout);
if (ret) {
return ret;
}
status = CAAM_RNG_GetRandomData(
config->base, &handle, kCAAM_RngStateHandle0,
&rng_buff_pool[0], read_length, kCAAM_RngDataAny, NULL);
k_sem_give(&mcux_caam_sem);
memcpy(&buffer[insert_idx], &rng_buff_pool[0], read_length);
insert_idx += read_length;
}