linux-kernel - Re: [PATCH] crypto: caam - adjust RNG timing to support more devices

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Date:   Mon, 17 Jul 2023 14:43:34 +0200
From:   Bastian Krause <bst@...gutronix.de>
To:     meenakshi.aggarwal@....com, horia.geanta@....com, V.sethi@....com,
        pankaj.gupta@....com, gaurav.jain@....com,
        herbert@...dor.apana.org.au, davem@...emloft.net,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Victoria Milhoan <vicki.milhoan@...escale.com>,
        Dan Douglass <dan.douglass@....com>,
        Vipul Kumar <vipul_kumar@...tor.com>, kernel@...gutronix.de
Subject: Re: [PATCH] crypto: caam - adjust RNG timing to support more devices

On 6/12/23 10:26, meenakshi.aggarwal@....com wrote:
> From: Victoria Milhoan <vicki.milhoan@...escale.com>
> 
> Adjust RNG timing parameters to support more i.MX6 devices.
> 
> Signed-off-by: Victoria Milhoan <vicki.milhoan@...escale.com>
> Signed-off-by: Dan Douglass <dan.douglass@....com>
> Signed-off-by: Vipul Kumar <vipul_kumar@...tor.com>
> Signed-off-by: Horia Geantă <horia.geanta@....com>
> ---
>   drivers/crypto/caam/ctrl.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)

This patch seems to breaks CAAM RNG instantiation on an i.MX8MM at my end:

caam 30900000.crypto: Entropy delay = 3200
caam 30900000.crypto: Entropy delay = 3600
[...]
caam 30900000.crypto: Entropy delay = 12400
caam 30900000.crypto: failed to instantiate RNG
caam: probe of 30900000.crypto failed with error -11

If I revert this patch or increase RTSDCTL_ENT_DLY_MAX to a value > 
66800, it works again:

caam 30900000.crypto: Entropy delay = 32800
caam 30900000.crypto: Entropy delay = 33200
[...]
caam 30900000.crypto: Entropy delay = 66800
caam 30900000.crypto: Instantiated RNG4 SH0
caam 30900000.crypto: Instantiated RNG4 SH1
caam 30900000.crypto: device ID = 0x0a16040100000000 (Era 9)
caam 30900000.crypto: job rings = 2, qi = 0
caam algorithms registered in /proc/crypto
caam 30900000.crypto: caam pkc algorithms registered in /proc/crypto
caam 30900000.crypto: registering rng-caam
Executing RNG SELF-TEST with wait
random: crng init done
caam 30900000.crypto: rng crypto API alg registered prng-caam

Regards,
Bastian

> 
> diff --git a/drivers/crypto/caam/ctrl.c b/drivers/crypto/caam/ctrl.c
> index 5fed3cf354c0..62dd069942e4 100644
> --- a/drivers/crypto/caam/ctrl.c
> +++ b/drivers/crypto/caam/ctrl.c
> @@ -383,8 +383,8 @@ static void kick_trng(struct device *dev, int ent_delay)
>   	wr_reg32(&r4tst->rtsdctl, val);
>   	/* min. freq. count, equal to 1/4 of the entropy sample length */
>   	wr_reg32(&r4tst->rtfrqmin, ent_delay >> 2);
> -	/* disable maximum frequency count */
> -	wr_reg32(&r4tst->rtfrqmax, RTFRQMAX_DISABLE);
> +	/* max. freq. count, equal to 16 times the entropy sample length */
> +	wr_reg32(&r4tst->rtfrqmax, ent_delay << 4);
>   	/* read the control register */
>   	val = rd_reg32(&r4tst->rtmctl);
>   start_rng:

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