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drivers: entropy: stm32: clear data available IRQ flag on WB09

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The STM32WB09 TRNG does not clear FIFO_FULL IRQ flag in hardware once the
FIFO is no longer full, a behavior which differs from all other series.
This results in spurious IRQs, as the TRNG IRQ line effectively remains
high forever once a single interrupt has been generated.

Clear the flag in software after reading from the FIFO on STM32WB09 SoC.

N.B.: the error IRQ flag is already handled properly, as this flag must
also be cleared by software on other series.

Signed-off-by: Mathieu Choplain <mathieu.choplain@st.com>
This commit is contained in:
Mathieu Choplain 2025-03-19 15:32:16 +01:00 committed by Benjamin Cabé
parent 6cdc3ada3c
commit 7288223a28
1 changed files with 13 additions and 1 deletions
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14
drivers/entropy/entropy_stm32.h
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@ -91,7 +91,19 @@ static inline uint32_t ll_rng_is_active_drdy(RNG_TypeDef *RNGx)
static inline uint16_t ll_rng_read_rand_data(RNG_TypeDef *RNGx)
{
#if defined(CONFIG_SOC_STM32WB09XX)
return (uint16_t)LL_RNG_GetRndVal(RNGx);
uint16_t rnd = (uint16_t)LL_RNG_GetRndVal(RNGx);
/**
* STM32WB09 TRNG does not clear IRQ flags in hardware.
* We must clear the "FIFO full" flag now that we consumed data
* from it to ensure the TRNG's IRQ line goes back to low state.
*
* Raw register access is performed because STM32CubeWB0 v1.0.0
* package is lacking the LL function to clear IRQ flags.
*/
WRITE_REG(RNG->IRQ_SR, RNG_IRQ_SR_FF_FULL_IRQ);
return rnd;
#elif defined(CONFIG_SOC_SERIES_STM32WB0X)
/* STM32WB05 / STM32WB06 / STM32WB07 */
return LL_RNG_ReadRandData16(RNGx);