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References: <20200128110102.11522-1-martin@kaiser.cx> <20200128110102.11522-6-martin@kaiser.cx>
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From:   PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>
Date:   Wed, 12 Feb 2020 21:53:09 +0530
Message-ID: <CANc+2y6oasMLCzDJAebFca4yoWWTL4r3Esyws-K5EuMLwbuAqA@mail.gmail.com>
Subject: Re: [PATCH 5/6] hwrng: imx-rngc - check the rng type
To:     Martin Kaiser <martin@kaiser.cx>
Cc:     Herbert Xu <herbert@gondor.apana.org.au>,
        NXP Linux Team <linux-imx@nxp.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@vger.kernel.org>,
        linux-arm-kernel@lists.infradead.org,
        open list <linux-kernel@vger.kernel.org>
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Sender: linux-crypto-owner@vger.kernel.org
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On Tue, 28 Jan 2020 at 16:31, Martin Kaiser <martin@kaiser.cx> wrote:
>
> Read the rng type and hardware revision during probe. Fail the probe
> operation if the type is not one of rngc or rngb.
> (There's also an rnga type, which needs a different driver.)
>
> Display the type and revision in a debug print if probe was successful.
>
> Signed-off-by: Martin Kaiser <martin@kaiser.cx>
> ---
>  drivers/char/hw_random/imx-rngc.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/char/hw_random/imx-rngc.c b/drivers/char/hw_random/imx-rngc.c
> index 8222055b9e9b..27d85fced30b 100644
> --- a/drivers/char/hw_random/imx-rngc.c
> +++ b/drivers/char/hw_random/imx-rngc.c
> @@ -18,12 +18,22 @@
>  #include <linux/completion.h>
>  #include <linux/io.h>
>
> +#define RNGC_VER_ID                    0x0000
>  #define RNGC_COMMAND                   0x0004
>  #define RNGC_CONTROL                   0x0008
>  #define RNGC_STATUS                    0x000C
>  #define RNGC_ERROR                     0x0010
>  #define RNGC_FIFO                      0x0014
>
> +/* the fields in the ver id register */
> +#define RNGC_TYPE_SHIFT                28
> +#define RNGC_VER_MAJ_SHIFT             8
> +
> +/* the rng_type field */
> +#define RNGC_TYPE_RNGB                 0x1
> +#define RNGC_TYPE_RNGC                 0x2
> +
> +
>  #define RNGC_CMD_CLR_ERR               0x00000020
>  #define RNGC_CMD_CLR_INT               0x00000010
>  #define RNGC_CMD_SEED                  0x00000002
> @@ -212,6 +222,8 @@ static int imx_rngc_probe(struct platform_device *pdev)
>         struct imx_rngc *rngc;
>         int ret;
>         int irq;
> +       u32 ver_id;
> +       u8  rng_type;
>
>         rngc = devm_kzalloc(&pdev->dev, sizeof(*rngc), GFP_KERNEL);
>         if (!rngc)
> @@ -237,6 +249,17 @@ static int imx_rngc_probe(struct platform_device *pdev)
>         if (ret)
>                 return ret;
>
> +       ver_id = readl(rngc->base + RNGC_VER_ID);
> +       rng_type = ver_id >> RNGC_TYPE_SHIFT;
> +       /*
> +        * This driver supports only RNGC and RNGB. (There's a different
> +        * driver for RNGA.)
> +        */
> +       if (rng_type != RNGC_TYPE_RNGC && rng_type != RNGC_TYPE_RNGB) {
> +               ret = -ENODEV;
> +               goto err;
> +       }
> +
>         ret = devm_request_irq(&pdev->dev,
>                         irq, imx_rngc_irq, 0, pdev->name, (void *)rngc);
>         if (ret) {
> @@ -269,7 +292,10 @@ static int imx_rngc_probe(struct platform_device *pdev)
>                 goto err;
>         }
>
> -       dev_info(&pdev->dev, "Freescale RNGC registered.\n");
> +       dev_info(&pdev->dev,
> +               "Freescale RNG%c registered (HW revision %d.%02d)\n",
> +               rng_type == RNGC_TYPE_RNGB ? 'B' : 'C',
> +               (ver_id >> RNGC_VER_MAJ_SHIFT) & 0xff, ver_id & 0xff);
>         return 0;
>
>  err:
> --
> 2.20.1
>

Reviewed-by: PrasannaKumar Muralidharan <prasannatsmkumar@gmail.com>