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drivers: sam: entropy: implement get_entropy_isr

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The commit contributes the implementation of
get_entropy_isr API function for the SAM entropy
driver. The implementation is similar to get_entropy,
with the difference that it does not invoke k_yield()
when called with the ENTROPY_BUSYWAIT options flag set.
When the function is invoked without the ENTROPY_BUSYWAIT
flag, it simply returns whatever data is available,
without busy waiting on the RNG herdware.

Signed-off-by: Ioannis Glaropoulos <Ioannis.Glaropoulos@nordicsemi.no>
This commit is contained in:
Ioannis Glaropoulos 2019-08-23 14:00:19 +02:00
commit 99cca4672c
1 changed files with 70 additions and 6 deletions
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76
drivers/entropy/entropy_sam.c
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@ -18,7 +18,7 @@ struct trng_sam_dev_cfg {
#define DEV_CFG(dev) \ #define DEV_CFG(dev) \
((const struct trng_sam_dev_cfg *const)(dev)->config->config_info) ((const struct trng_sam_dev_cfg *const)(dev)->config->config_info)
static int entropy_sam_wait_ready(Trng *const trng) static int entropy_sam_wait_ready(Trng * const trng, u32_t flags)
{ {
/* According to the reference manual, the generator provides /* According to the reference manual, the generator provides
* one 32-bit random value every 84 peripheral clock cycles. * one 32-bit random value every 84 peripheral clock cycles.
@ -36,14 +36,23 @@ static int entropy_sam_wait_ready(Trng *const trng)
return -ETIMEDOUT; return -ETIMEDOUT;
} }
k_yield(); 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; return 0;
} }
static int entropy_sam_get_entropy(struct device *dev, u8_t *buffer, static int entropy_sam_get_entropy_internal(struct device *dev, u8_t *buffer,
u16_t length) u16_t length, u32_t flags)
{ {
Trng *const trng = DEV_CFG(dev)->regs; Trng *const trng = DEV_CFG(dev)->regs;
@ -52,7 +61,7 @@ static int entropy_sam_get_entropy(struct device *dev, u8_t *buffer,
u32_t value; u32_t value;
int res; int res;
res = entropy_sam_wait_ready(trng); res = entropy_sam_wait_ready(trng, flags);
if (res < 0) { if (res < 0) {
return res; return res;
} }
@ -68,6 +77,60 @@ static int entropy_sam_get_entropy(struct device *dev, u8_t *buffer,
return 0; return 0;
} }
static int entropy_sam_get_entropy(struct device *dev, u8_t *buffer,
u16_t length)
{
return entropy_sam_get_entropy_internal(dev, buffer, length, 0);
}
static int entropy_sam_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->TRNG_ISR & TRNG_ISR_DATRDY)) {
/* Data not ready */
break;
}
value = trng->TRNG_ODATA;
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_sam_get_entropy_internal(dev,
buffer, length, flags);
if (ret == 0) {
/* Data retrieved successfully. */
return cnt;
}
return ret;
}
}
static int entropy_sam_init(struct device *dev) static int entropy_sam_init(struct device *dev)
{ {
Trng *const trng = DEV_CFG(dev)->regs; Trng *const trng = DEV_CFG(dev)->regs;
@ -82,7 +145,8 @@ static int entropy_sam_init(struct device *dev)
} }
static const struct entropy_driver_api entropy_sam_api = { static const struct entropy_driver_api entropy_sam_api = {
.get_entropy = entropy_sam_get_entropy .get_entropy = entropy_sam_get_entropy,
.get_entropy_isr = entropy_sam_get_entropy_isr
}; };
static const struct trng_sam_dev_cfg trng_sam_cfg = { static const struct trng_sam_dev_cfg trng_sam_cfg = {