Reviewed-by: Vabhav Sharma <vabhav.sharma@xxxxxxx>
> -----Original Message-----
> From: Fabio Estevam <festevam@xxxxxxxxx>
> Sent: Wednesday, April 20, 2022 5:36 PM
> To: herbert@xxxxxxxxxxxxxxxxxxx
> Cc: Horia Geanta <horia.geanta@xxxxxxx>; Gaurav Jain
> <gaurav.jain@xxxxxxx>; Varun Sethi <V.Sethi@xxxxxxx>; linux-
> crypto@xxxxxxxxxxxxxxx; Fabio Estevam <festevam@xxxxxxx>;
> stable@xxxxxxxxxxxxxxx
> Subject: [PATCH v5] crypto: caam - fix i.MX6SX entropy delay value
>
> From: Fabio Estevam <festevam@xxxxxxx>
>
> 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@xxxxxxxxxxxxxxx>
> Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG")
> Signed-off-by: Fabio Estevam <festevam@xxxxxxx>
> Reviewed-by: Horia Geantă <horia.geanta@xxxxxxx>
> ---
> 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
