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From:   Vabhav Sharma <vabhav.sharma@nxp.com>
To:     "herbert@gondor.apana.org.au" <herbert@gondor.apana.org.au>,
        Fabio Estevam <festevam@gmail.com>
CC:     Horia Geanta <horia.geanta@nxp.com>,
        Gaurav Jain <gaurav.jain@nxp.com>,
        Varun Sethi <V.Sethi@nxp.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>,
        Fabio Estevam <festevam@denx.de>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: RE: [EXT] [PATCH v4] crypto: caam - fix i.MX6SX entropy delay value
Thread-Topic: [EXT] [PATCH v4] crypto: caam - fix i.MX6SX entropy delay value
Thread-Index: AQHYU+LsYV+G5+/ss0KzziVmGUYIJqz4PoFQgABfLYA=
Date:   Wed, 20 Apr 2022 11:34:28 +0000
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> -----Original Message-----
> From: Fabio Estevam <festevam@gmail.com>
> Sent: Tuesday, April 19, 2022 5:15 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: [EXT] [PATCH v4] crypto: caam - fix i.MX6SX entropy delay value
>=20
> Caution: EXT Email
>=20
> From: Fabio Estevam <festevam@denx.de>
>=20
> Since commit 358ba762d9f1 ("crypto: caam - enable prediction resistance i=
n
> HRWNG") the following CAAM errors can be seen on i.MX6SX:
>=20
> caam_jr 2101000.jr: 20003c5b: CCB: desc idx 60: RNG: Hardware error
> hwrng: no data available
>=20
> This error is due to an incorrect entropy delay for i.MX6SX.
>=20
> Fix it by increasing the minimum entropy delay for i.MX6SX as done in U-B=
oot:
> https://eur01.safelinks.protection.outlook.com/?url=3Dhttps%3A%2F%2Fpatch
> work.ozlabs.org%2Fproject%2Fuboot%2Fpatch%2F20220415111049.2565744-
> 1-
> gaurav.jain%40nxp.com%2F&amp;data=3D05%7C01%7Cgaurav.jain%40nxp.co
> m%7C9016fe4b6bb8402de08f08da21fa0703%7C686ea1d3bc2b4c6fa92cd99c5c
> 301635%7C0%7C0%7C637859655100732358%7CUnknown%7CTWFpbGZsb3d8
> eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3
> D%7C3000%7C%7C%7C&amp;sdata=3DwglpvZBmQUKn7sLRx5xpdwdgFMOc6LE
> qIMqUU0h4UZE%3D&amp;reserved=3D0
>=20
> Cc: <stable@vger.kernel.org>
> Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWN=
G")
> 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.
>=20
>  drivers/crypto/caam/ctrl.c | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>=20
> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c inde=
x
> 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
>=20
> +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 cha=
nge
>                          * the TRNG parameters.
>                          */
> +                       if (needs_extended_entropy_delay())
> +                               ent_delay =3D 12000;
>                         if (!(ctrlpriv->rng4_sh_init || inst_handles)) {
Please note if TRNG state handles are already instantiated e.g. by U-Boot b=
ootloader, It is assumed that entropy is set correctly and kick_trng() will=
 be skipped
Kindly pick the U-Boot changes as detailed in commit message.
>                                 dev_info(dev,
>                                          "Entropy delay =3D %u\n", @@ -87=
1,6 +880,15 @@ static
> int caam_probe(struct platform_device *pdev)
>                          */
>                         ret =3D instantiate_rng(dev, inst_handles,
>                                               gen_sk);
> +                       /*
> +                        * Entropy delay is determined via TRNG character=
ization.
> +                        * 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())
There is nothing like extended entropy delay and function name seems to be =
incorrect, The software test were run offline across ranges of temperature,=
 voltage and process to determine the correct entropy delay.
However, value of 12000 is determined by running said test across voltage a=
nd temperature only for iMX6SX.
> +                               break;
>                         if (ret =3D=3D -EAGAIN)
>                                 /*
>                                  * if here, the loop will rerun,
> --
> 2.25.1