RE: [PATCH v5] crypto: caam - fix i.MX6SX entropy delay value

Reviewed-by: Vabhav Sharma vabhav.sharma@nxp.com

-----Original Message----- From: Fabio Estevam festevam@gmail.com Sent: Wednesday, April 20, 2022 5:36 PM To: herbert@gondor.apana.org.au Cc: Horia Geanta horia.geanta@nxp.com; Gaurav Jain gaurav.jain@nxp.com; Varun Sethi V.Sethi@nxp.com; linux- crypto@vger.kernel.org; Fabio Estevam festevam@denx.de; stable@vger.kernel.org Subject: [PATCH v5] crypto: caam - fix i.MX6SX entropy delay value

From: Fabio Estevam festevam@denx.de

Since commit 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG") the following CAAM errors can be seen on i.MX6SX:

caam_jr 2101000.jr: 20003c5b: CCB: desc idx 60: RNG: Hardware error hwrng: no data available

This error is due to an incorrect entropy delay for i.MX6SX.

Fix it by increasing the minimum entropy delay for i.MX6SX as done in U-Boot: https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatch work.ozlabs.org%2Fproject%2Fuboot%2Fpatch%2F20220415111049.2565744- 1- gaurav.jain%40nxp.com%2F&data=05%7C01%7Cmeenakshi.aggarwal%4 0nxp.com%7Caf57d0186dde479aa9cf08da22c687d0%7C686ea1d3bc2b4c6fa92 cd99c5c301635%7C0%7C0%7C637860533324307730%7CUnknown%7CTWFpb GZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI 6Mn0%3D%7C3000%7C%7C%7C&sdata=UhqjgESpgMhOhJS%2BT4ghI6y NIvyybOI8yEv5%2FjKNcDE%3D&reserved=0

As explained in the U-Boot patch:

"RNG self tests are run to determine the correct entropy delay. Such tests are executed with different voltages and temperatures to identify the worst case value for the entropy delay. For i.MX6SX, it was determined that after adding a margin value of 1000 the minimum entropy delay should be at least 12000."

Cc: stable@vger.kernel.org Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG") Signed-off-by: Fabio Estevam festevam@denx.de Reviewed-by: Horia Geantă horia.geanta@nxp.com

---

Changes since v4:

• Change the function name to needs_entropy_delay_adjustment() -

Vabhav

• Improve the commit log by adding the explanation from the U-Boot patch -

Vabhav

drivers/crypto/caam/ctrl.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)

diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c index ca0361b2dbb0..f87aa2169e5f 100644 --- a/drivers/crypto/caam/ctrl.c +++ b/drivers/crypto/caam/ctrl.c @@ -609,6 +609,13 @@ static bool check_version(struct fsl_mc_version *mc_version, u32 major, } #endif

+static bool needs_entropy_delay_adjustment(void) +{

• if (of_machine_is_compatible("fsl,imx6sx"))

• return true;
  

• return false;

+}

/* Probe routine for CAAM top (controller) level */ static int caam_probe(struct platform_device *pdev) { @@ -855,6 +862,8 @@ static int caam_probe(struct platform_device *pdev) * Also, if a handle was instantiated, do not change * the TRNG parameters. */

• 	if (needs_entropy_delay_adjustment())
  

• 		ent_delay = 12000;
  if (!(ctrlpriv->rng4_sh_init || inst_handles)) {
  	dev_info(dev,
  		 "Entropy delay = %u\n",
  

@@ -871,6 +880,15 @@ static int caam_probe(struct platform_device *pdev) */ ret = instantiate_rng(dev, inst_handles, gen_sk);

• 	/*
  

• 	 * Entropy delay is determined via TRNG
  

characterization.

• 	 * TRNG characterization is run across different
  

voltages

• 	 * and temperatures.
  

• 	 * If worst case value for ent_dly is identified,
  

• 	 * the loop can be skipped for that platform.
  

• 	 */
  

• 	if (needs_entropy_delay_adjustment())
  

• 		break;
  if (ret == -EAGAIN)
  	/*
  	 * if here, the loop will rerun,
  

-- 2.25.1