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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: [PATCH v5] crypto: caam - fix i.MX6SX entropy delay value
Thread-Topic: [PATCH v5] crypto: caam - fix i.MX6SX entropy delay value
Thread-Index: AQHYVK9m3zqP4sIQMUeYfZzjEtnCmaz6NsWggAAZwPA=
Date:   Thu, 21 Apr 2022 12:51:48 +0000
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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
>=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%7Cmeenakshi.aggarwal%4
> 0nxp.com%7Caf57d0186dde479aa9cf08da22c687d0%7C686ea1d3bc2b4c6fa92
> cd99c5c301635%7C0%7C0%7C637860533324307730%7CUnknown%7CTWFpb
> GZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI
> 6Mn0%3D%7C3000%7C%7C%7C&amp;sdata=3DUhqjgESpgMhOhJS%2BT4ghI6y
> NIvyybOI8yEv5%2FjKNcDE%3D&amp;reserved=3D0
>=20
> As explained in the U-Boot patch:
>=20
> "RNG self tests are run to determine the correct entropy delay.
> Such tests are executed with different voltages and temperatures to ident=
ify
> the worst case value for the entropy delay. For i.MX6SX, it was determine=
d
> that after adding a margin value of 1000 the minimum entropy delay should
> be at least 12000."
>=20
> Cc: <stable@vger.kernel.org>
> Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWN=
G")
> Signed-off-by: Fabio Estevam <festevam@denx.de>
> Reviewed-by: Horia Geant=E3 <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
>=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..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
>=20
> +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 =3D 12000;
>  			if (!(ctrlpriv->rng4_sh_init || inst_handles)) {
>  				dev_info(dev,
>  					 "Entropy delay =3D %u\n",
> @@ -871,6 +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
> 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 =3D=3D -EAGAIN)
>  				/*
>  				 * if here, the loop will rerun,
> --
> 2.25.1