drivers: stm32_rng: ensure conditional reset sequence is done

Add a check on RNG_CR_CONDRST being cleared before continuing the program to ensure that the conditional reset sequence is done. Signed-off-by: Gatien Chevallier <[email protected]> Reviewed-by: Etienne Carriere <[email protected]>
qazwsxedcrfvtg14 · Jan 10, 2024 · eb5cf77 · eb5cf77
1 parent c2c5b4b
commit eb5cf77
Showing 1 changed file with 16 additions and 1 deletion.
diff --git a/core/drivers/stm32_rng.c b/core/drivers/stm32_rng.c
@@ -279,9 +279,15 @@ static TEE_Result init_rng(void)
 		io_clrsetbits32(rng_base + RNG_CR, RNG_CR_CLKDIV,
 				clock_div << RNG_CR_CLKDIV_SHIFT);
 
-		/* No need to wait for RNG_CR_CONDRST toggle as we enable clk */
 		io_clrsetbits32(rng_base + RNG_CR, RNG_CR_CONDRST,
 				RNG_CR_RNGEN);
+
+		timeout_ref = timeout_init_us(RNG_READY_TIMEOUT_US);
+		while (io_read32(rng_base + RNG_CR) & RNG_CR_CONDRST)
+			if (timeout_elapsed(timeout_ref))
+				break;
+		if (io_read32(rng_base + RNG_CR) & RNG_CR_CONDRST)
+			panic();
 	} else {
 		io_setbits32(rng_base + RNG_CR, RNG_CR_RNGEN | cr_ced_mask);
 	}
@@ -391,6 +397,8 @@ static TEE_Result stm32_rng_pm_resume(uint32_t pm_cr)
 	io_write32(base + RNG_SR, 0);
 
 	if (stm32_rng->ddata->has_cond_reset) {
+		uint64_t timeout_ref = 0;
+
 		/*
 		 * Configuration must be set in the same access that sets
 		 * RNG_CR_CONDRST bit. Otherwise, the configuration setting is
@@ -400,6 +408,13 @@ static TEE_Result stm32_rng_pm_resume(uint32_t pm_cr)
 		io_write32(base + RNG_CR, pm_cr | RNG_CR_CONDRST);
 
 		io_clrsetbits32(base + RNG_CR, RNG_CR_CONDRST, RNG_CR_RNGEN);
+
+		timeout_ref = timeout_init_us(RNG_READY_TIMEOUT_US);
+		while (io_read32(base + RNG_CR) & RNG_CR_CONDRST)
+			if (timeout_elapsed(timeout_ref))
+				break;
+		if (io_read32(base + RNG_CR) & RNG_CR_CONDRST)
+			panic();
 	} else {
 		io_write32(base + RNG_CR, RNG_CR_RNGEN | pm_cr);
 	}