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://patchwork.ozlabs.org/project/uboot/patch/20220415111049.2565744-1-ga...

Cc: stable@vger.kernel.org Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG") Signed-off-by: Fabio Estevam festevam@denx.de --- Changes since v3: - Add a needs_extended_entropy_delay() function - Assign the 'ent_delay' inside the the RNG initialization area. (Horia) - Change the terminology as per Horia's explanation.

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..5b989a842ee9 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_extended_entropy_delay(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_extended_entropy_delay()) + 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_extended_entropy_delay()) + break; if (ret == -EAGAIN) /* * if here, the loop will rerun,