Commit b17bc6eb authored by Gatien Chevallier's avatar Gatien Chevallier Committed by Herbert Xu
Browse files

hwrng: stm32 - rework error handling in stm32_rng_read() 



Try to conceal seed errors when possible. If, despite the error
concealing tries, a seed error is still present, then return an error.

A clock error does not compromise the hardware block and data can
still be read from RNG_DR. Just warn that the RNG clock is too slow
and clear RNG_SR.

Signed-off-by: default avatarGatien Chevallier <gatien.chevallier@foss.st.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
parent 8f1c5227

drivers/char/hw_random/stm32-rng.c

+41 −12
Original line number Diff line number Diff line
@@ -43,6 +43,8 @@ 


#define RNG_HTCR		0x10



#define RNG_NB_RECOVER_TRIES	3



struct stm32_rng_data {

	u32	cr;

	u32	nscr;
@@ -162,10 +164,10 @@ static int stm32_rng_conceal_seed_error(struct hwrng *rng) 


static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)

{

	struct stm32_rng_private *priv =

	    container_of(rng, struct stm32_rng_private, rng);

	struct stm32_rng_private *priv = container_of(rng, struct stm32_rng_private, rng);

	unsigned int i = 0;

	int retval = 0, err = 0;

	u32 sr;

	int retval = 0;



	pm_runtime_get_sync((struct device *) priv->rng.priv);
@@ -174,30 +176,57 @@ static int stm32_rng_read(struct hwrng *rng, void *data, size_t max, bool wait) 


	while (max >= sizeof(u32)) {

		sr = readl_relaxed(priv->base + RNG_SR);

		/* Manage timeout which is based on timer and take */

		/* care of initial delay time when enabling rng	*/

		/*

		 * Manage timeout which is based on timer and take

		 * care of initial delay time when enabling the RNG.

		 */

		if (!sr && wait) {

			int err;



			err = readl_relaxed_poll_timeout_atomic(priv->base

								   + RNG_SR,

								   sr, sr,

								   10, 50000);

			if (err)

			if (err) {

				dev_err((struct device *)priv->rng.priv,

					"%s: timeout %x!\n", __func__, sr);

				break;

			}

		} else if (!sr) {

			/* The FIFO is being filled up */

			break;

		}



		/* If error detected or data not ready... */

		if (sr != RNG_SR_DRDY) {

			if (WARN_ONCE(sr & (RNG_SR_SEIS | RNG_SR_CEIS),

					"bad RNG status - %x\n", sr))

			if (sr & RNG_SR_SEIS) {

				err = stm32_rng_conceal_seed_error(rng);

				i++;

				if (err && i > RNG_NB_RECOVER_TRIES) {

					dev_err((struct device *)priv->rng.priv,

						"Couldn't recover from seed error\n");

					return -ENOTRECOVERABLE;

				}



				continue;

			}



			if (WARN_ONCE((sr & RNG_SR_CEIS), "RNG clock too slow - %x\n", sr))

				writel_relaxed(0, priv->base + RNG_SR);

			break;

		}



		/* Late seed error case: DR being 0 is an error status */

		*(u32 *)data = readl_relaxed(priv->base + RNG_DR);

		if (!*(u32 *)data) {

			err = stm32_rng_conceal_seed_error(rng);

			i++;

			if (err && i > RNG_NB_RECOVER_TRIES) {

				dev_err((struct device *)priv->rng.priv,

					"Couldn't recover from seed error");

				return -ENOTRECOVERABLE;

			}



			continue;

		}



		i = 0;

		retval += sizeof(u32);

		data += sizeof(u32);

		max -= sizeof(u32);