nrf_security: CRACEN: Add workaround for trng on CRACEN lite

CRACEN lite has the wrong configuration for TRNG.
Add workaround to set these directly during startup of TRNG
This might be possible to remove in the future

Signed-off-by: Dag Erik Gjørvad <[email protected]>

Author: degjorva

subsys/nrf_security/src/drivers/cracen/sxsymcrypt/src/ba431regs.h

@@ -29,6 +29,10 @@
 #define BA431_REG_Key3_OFST			(0x1Cu)
 /** TestData: Test data register. */
 #define  BA431_REG_TestData_OFST                (0x20u)
+/** RepeatThreshold: Repetition test cut-off register. */
+#define  BA431_REG_REPEATTHRESHOLD              (0x24u)
+/** PropThreshold: Proportion test cut-off. */
+#define  BA431_REG_PROPTHRESHOLD                (0x28u)
 /** Status: Status register. */
 #define BA431_REG_Status_OFST			(0x30u)
 /** InitWaitVal: Initial wait counter value. */

subsys/nrf_security/src/drivers/cracen/sxsymcrypt/src/trng.c

@@ -27,6 +27,11 @@
 			  BA431_FLD_Control_HealthTestBypass_MASK | \
 			  BA431_FLD_Control_Conditioning_Bypass_MASK)
 
+#if defined(CONFIG_CRACEN_HW_VERSION_LITE)
+#define RNG_REPEATTHRESHOLD_VAL (21)
+#define RNG_PROPTESTCUTOFF_VAL	(311)
+#endif
+
 static int ba431_check_state(void)
 {
 	uint32_t state = sx_rd_trng(BA431_REG_Status_OFST);
@@ -115,6 +120,13 @@ int sx_trng_open(struct sx_trng *ctx, const struct sx_trng_config *config)
 	sx_wr_trng(BA431_REG_ClkDiv_OFST, rng_clkdiv);
 	sx_wr_trng(BA431_REG_InitWaitVal_OFST, rng_init_wait_val);
 
+	/* CRACEN Lite has incorrect values for the TRNG tests. We update these here as a workaround
+	 */
+#if defined(CONFIG_CRACEN_HW_VERSION_LITE)
+	sx_wr_trng(BA431_REG_REPEATTHRESHOLD, RNG_REPEATTHRESHOLD_VAL);
+	sx_wr_trng(BA431_REG_PROPTHRESHOLD, RNG_PROPTESTCUTOFF_VAL);
+#endif /* CONFIG_CRACEN_HW_VERSION_LITE */
+
 	/* Configure the control register and set the enable bit */
 	control = (RNG_NB_128BIT_BLOCKS << BA431_FLD_Control_Nb128BitBlocks_LSB);
 	control |= ctrlbitmask;