linux-kernel - Re: [PATCH v5 2/3] hw_random: cctrng: introduce Arm CryptoCell driver

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Message-ID: <412a4da61063b8c8a72729f03c06480c5f1374fb.camel@pengutronix.de>
Date:   Mon, 23 Mar 2020 15:56:19 +0100
From:   Rouven Czerwinski <r.czerwinski@...gutronix.de>
To:     Hadar Gat <hadar.gat@....com>, Matt Mackall <mpm@...enic.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Florian Fainelli <f.fainelli@...il.com>,
        Alexander Sverdlin <alexander.sverdlin@...ia.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tomer Maimon <tmaimon77@...il.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Zaibo Xu <xuzaibo@...wei.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc:     linux-crypto@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Gilad Ben-Yossef <gilad@...yossef.com>,
        Ofir Drang <ofir.drang@....com>
Subject: Re: [PATCH v5 2/3] hw_random: cctrng: introduce Arm CryptoCell
 driver

Hello Hadar,

On Sun, 2020-03-22 at 17:31 +0200, Hadar Gat wrote:
> Introduce low level Arm CryptoCell TRNG HW support.
> 
> Signed-off-by: Hadar Gat <hadar.gat@....com>
> ---
>  drivers/char/hw_random/Kconfig  |  12 +
>  drivers/char/hw_random/Makefile |   1 +
>  drivers/char/hw_random/cctrng.c | 735
> ++++++++++++++++++++++++++++++++++++++++
>  drivers/char/hw_random/cctrng.h |  69 ++++
>  4 files changed, 817 insertions(+)
>  create mode 100644 drivers/char/hw_random/cctrng.c
>  create mode 100644 drivers/char/hw_random/cctrng.h
> 
> [...]
> +static int cctrng_probe(struct platform_device *pdev)
> +{
> +	struct resource *req_mem_cc_regs = NULL;
> +	struct cctrng_drvdata *drvdata;
> +	struct device *dev = &pdev->dev;
> +	int rc = 0;
> +	u32 val;
> +	int irq;
> +
> +	drvdata = devm_kzalloc(dev, sizeof(*drvdata), GFP_KERNEL);
> +	if (!drvdata)
> +		return -ENOMEM;
> +
> +	drvdata->rng.name = devm_kstrdup(dev, dev_name(dev),
> GFP_KERNEL);
> +	if (!drvdata->rng.name)
> +		return -ENOMEM;
> +
> +	drvdata->rng.read = cctrng_read;
> +	drvdata->rng.priv = (unsigned long)drvdata;

You are not initializing drvdata->rng.quality to a default value, which
results in the TRNG not being used by the kernel by default. If its a
perfect TRNG this should be set to 1024, i.e. 1024 bits of entropy per
1024 bits of input.

Regards,
Rouven Czerwinski