Hi Fabio,
Vabhav is working on a fix for the Linux driver. He would be introducing a new property in the CAAM device tree node, which would be used for specifying the entropy delay value. This would make the solution generic. This property is optional.
Also, please note that the entropy delay value has been derived for i.MX6SX after a silicon characterization study.
Regards
Varun
> -----Original Message-----
> From: Fabio Estevam <festevam@xxxxxxxxx>
> Sent: Saturday, April 16, 2022 7:24 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>
> Subject: [EXT] [PATCH v2] crypto: caam - fix i.MX6SX entropy delay value
>
> Caution: EXT Email
>
> 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
> caam_jr 2101000.jr: 20003c5b: CCB: desc idx 60: RNG: Hardware error ...
>
> 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%2Fpatchwo
> rk.ozlabs.org%2Fproject%2Fuboot%2Fpatch%2F20220415111049.2565744-1-
> gaurav.jain%40nxp.com%2F&data=04%7C01%7CV.Sethi%40nxp.com%7C7
> 9659c64ea334807ca2c08da1fb0b1b3%7C686ea1d3bc2b4c6fa92cd99c5c301635
> %7C0%7C0%7C637857141005203180%7CUnknown%7CTWFpbGZsb3d8eyJWIjoi
> MC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000
> &sdata=%2BpR3ecPQNZ001zRGWe%2FWo%2FayfltO6zYK1p%2BwQ57c6J
> U%3D&reserved=0
>
> Signed-off-by: Fabio Estevam <festevam@xxxxxxx>
> ---
> Change since v1:
> - Align the fix with U-Boot.
>
> drivers/crypto/caam/ctrl.c | 11 +++++++++++
> 1 file changed, 11 insertions(+)
>
> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c index
> ca0361b2dbb0..c515c20442d5 100644
> --- a/drivers/crypto/caam/ctrl.c
> +++ b/drivers/crypto/caam/ctrl.c
> @@ -648,6 +648,8 @@ static int caam_probe(struct platform_device *pdev)
> return ret;
> }
>
> + if (of_machine_is_compatible("fsl,imx6sx"))
> + ent_delay = 12000;
>
> /* Get configuration properties from device tree */
> /* First, get register page */
> @@ -871,6 +873,15 @@ static int caam_probe(struct platform_device *pdev)
> */
> ret = instantiate_rng(dev, inst_handles,
> gen_sk);
> + /*
> + * Entropy delay is calculated via self-test method.
> + * Self-test 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 (of_machine_is_compatible("fsl,imx6sx"))
> + break;
> if (ret == -EAGAIN)
> /*
> * if here, the loop will rerun,
> --
> 2.25.1
