[Varun Sethi <V.Sethi@nxp.com>]

Hi Fabio, Andrey,
So far we have observed this issue on i.MX6 only. Disabling prediction resistance isn't the solution for the problem. We are working on identifying the proper fix for this issue and would post the patch for the same.

Regards
Varun
>>On Tue, Jan 11, 2022 at 4:41 AM Fabio Estevam <festevam@gmail.com> wrote:
>>
>> From: Fabio Estevam <festevam@denx.de>
>>
>> Since commit 358ba762d9f1 ("crypto: caam - enable prediction resistance
>> in HRWNG") the following CAAM errors can be seen on i.MX6:
>>
>> 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
>> hwrng: no data available
>> 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
>> hwrng: no data available
>>
>> OP_ALG_PR_ON is enabled unconditionally, which may cause the problem
>> on i.MX devices.

>Is this true for every i.MX device? I haven't worked with the
>i.MX6Q/i.MX8 hardware I was enabling this feature for in a while, so
>I'm not 100% up to date on all of the problems we've seen with those,
>but last time enabling prediction resistance didn't seem to cause any
>issues besides a noticeable slowdown of random data generation.

>Can this be a Kconfig option or maybe a runtime flag so that it'd
>still be possible for some i.MX users to keep PR enabled?

>>
>> Fix the problem by only enabling OP_ALG_PR_ON on platforms that have
> >Management Complex support.
>>
> >Fixes: 358ba762d9f1 ("crypto: caam - enable prediction resistance in HRWNG")
> >Signed-off-by: Fabio Estevam <festevam@denx.de>
> >---
>  >drivers/crypto/caam/caamrng.c | 15 +++++++++++----
> > 1 file changed, 11 insertions(+), 4 deletions(-)
>>
> >diff --git a/drivers/crypto/caam/caamrng.c b/drivers/crypto/caam/caamrng.c
> >index 77d048dfe5d0..3514fe5de2a5 100644
> >--- a/drivers/crypto/caam/caamrng.c
> >+++ b/drivers/crypto/caam/caamrng.c
> >@@ -63,12 +63,19 @@ static void caam_rng_done(struct device *jrdev, u32 *desc, u32 err,
> >        complete(jctx->done);
> > }
>>
> >-static u32 *caam_init_desc(u32 *desc, dma_addr_t dst_dma)
>> +static u32 *caam_init_desc(struct device *jrdev, u32 *desc, dma_addr_t dst_dma)
> > {
>> +       struct caam_drv_private *priv = dev_get_drvdata(jrdev->parent);
> >+
> >        init_job_desc(desc, 0); /* + 1 cmd_sz */
> >        /* Generate random bytes: + 1 cmd_sz */
> >-       append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG |
>> -                        OP_ALG_PR_ON);
>> +
>> +       if (priv->mc_en)
>> +               append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG |
>> +                                 OP_ALG_PR_ON);
>> +       else
>> +               append_operation(desc, OP_ALG_ALGSEL_RNG | OP_TYPE_CLASS1_ALG);
>> +
> >        /* Store bytes: + 1 cmd_sz + caam_ptr_sz  */
> >        append_fifo_store(desc, dst_dma,
> >                          CAAM_RNG_MAX_FIFO_STORE_SIZE, FIFOST_TYPE_RNGSTORE);
> >@@ -101,7 +108,7 @@ static int caam_rng_read_one(struct device *jrdev,
>>
> >        init_completion(done);
> >        err = caam_jr_enqueue(jrdev,
>> -                             caam_init_desc(desc, dst_dma),
>> +                             caam_init_desc(jrdev, desc, dst_dma),
> >                              caam_rng_done, &jctx);
>>        if (err == -EINPROGRESS) {
> >                wait_for_completion(done);
>> --
> 2.25.1
>