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Message-ID: <CANc+2y63p1b5ATDY0oU4nLckk9CJhSs3CXGHy=NwoXn_awP9aA@mail.gmail.com>
Date: Tue, 18 Oct 2016 21:39:17 +0530
From: PrasannaKumar Muralidharan <prasannatsmkumar@...il.com>
To: Corentin Labbe <clabbe.montjoie@...il.com>
Cc: Herbert Xu <herbert@...dor.apana.org.au>, davem@...emloft.net,
maxime.ripard@...e-electrons.com, wens@...e.org,
linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] crypto: sun4i-ss: support the Security System PRNG
Hi Corentin,
I have a few minor comments.
On 18 October 2016 at 18:04, Corentin Labbe <clabbe.montjoie@...il.com> wrote:
> From: LABBE Corentin <clabbe.montjoie@...il.com>
>
> The Security System have a PRNG.
> This patch add support for it as an hwrng.
>
> Signed-off-by: Corentin Labbe <clabbe.montjoie@...il.com>
> ---
> drivers/crypto/Kconfig | 8 ++++
> drivers/crypto/sunxi-ss/Makefile | 1 +
> drivers/crypto/sunxi-ss/sun4i-ss-core.c | 14 +++++++
> drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c | 70 ++++++++++++++++++++++++++++++++
> drivers/crypto/sunxi-ss/sun4i-ss.h | 8 ++++
> 5 files changed, 101 insertions(+)
> create mode 100644 drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
>
> diff --git a/drivers/crypto/Kconfig b/drivers/crypto/Kconfig
> index 4d2b81f..38f7aca 100644
> --- a/drivers/crypto/Kconfig
> +++ b/drivers/crypto/Kconfig
> @@ -538,6 +538,14 @@ config CRYPTO_DEV_SUN4I_SS
> To compile this driver as a module, choose M here: the module
> will be called sun4i-ss.
>
> +config CRYPTO_DEV_SUN4I_SS_PRNG
> + bool "Support for Allwinner Security System PRNG"
> + depends on CRYPTO_DEV_SUN4I_SS
> + select HW_RANDOM
> + help
> + This driver provides kernel-side support for the Pseudo-Random
> + Number Generator found in the Security System.
> +
> config CRYPTO_DEV_ROCKCHIP
> tristate "Rockchip's Cryptographic Engine driver"
> depends on OF && ARCH_ROCKCHIP
> diff --git a/drivers/crypto/sunxi-ss/Makefile b/drivers/crypto/sunxi-ss/Makefile
> index 8f4c7a2..ca049ee 100644
> --- a/drivers/crypto/sunxi-ss/Makefile
> +++ b/drivers/crypto/sunxi-ss/Makefile
> @@ -1,2 +1,3 @@
> obj-$(CONFIG_CRYPTO_DEV_SUN4I_SS) += sun4i-ss.o
> sun4i-ss-y += sun4i-ss-core.o sun4i-ss-hash.o sun4i-ss-cipher.o
> +sun4i-ss-$(CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG) += sun4i-ss-hwrng.o
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-core.c b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> index 3ac6c6c..fa739de 100644
> --- a/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss-core.c
> @@ -359,6 +359,16 @@ static int sun4i_ss_probe(struct platform_device *pdev)
> }
> }
> platform_set_drvdata(pdev, ss);
> +
> +#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
> + /* Voluntarily made the PRNG optional */
> + err = sun4i_ss_hwrng_register(&ss->hwrng);
> + if (!err)
> + dev_info(ss->dev, "sun4i-ss PRNG loaded");
> + else
> + dev_err(ss->dev, "sun4i-ss PRNG failed");
> +#endif
> +
> return 0;
> error_alg:
> i--;
> @@ -386,6 +396,10 @@ static int sun4i_ss_remove(struct platform_device *pdev)
> int i;
> struct sun4i_ss_ctx *ss = platform_get_drvdata(pdev);
>
> +#ifdef CONFIG_CRYPTO_DEV_SUN4I_SS_PRNG
> + sun4i_ss_hwrng_remove(&ss->hwrng);
> +#endif
> +
> for (i = 0; i < ARRAY_SIZE(ss_algs); i++) {
> switch (ss_algs[i].type) {
> case CRYPTO_ALG_TYPE_ABLKCIPHER:
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
> new file mode 100644
> index 0000000..95fadb7
> --- /dev/null
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss-hwrng.c
> @@ -0,0 +1,70 @@
> +#include "sun4i-ss.h"
> +
> +static int sun4i_ss_hwrng_init(struct hwrng *hwrng)
> +{
> + struct sun4i_ss_ctx *ss;
> +
> + ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
> + get_random_bytes(ss->seed, SS_SEED_LEN);
> +
> + return 0;
> +}
> +
> +static int sun4i_ss_hwrng_read(struct hwrng *hwrng, void *buf,
> + size_t max, bool wait)
> +{
> + int i;
> + u32 v;
> + u32 *data = buf;
> + const u32 mode = SS_OP_PRNG | SS_PRNG_CONTINUE | SS_ENABLED;
> + size_t len;
> + struct sun4i_ss_ctx *ss;
> +
> + ss = container_of(hwrng, struct sun4i_ss_ctx, hwrng);
> + len = min_t(size_t, SS_DATA_LEN, max);
> +
> + spin_lock_bh(&ss->slock);
Is spin_lock_bh really required here? I could see it is being used in
sun4i-ss-hash.c but could not find any comment/info about the need.
> + writel(mode, ss->base + SS_CTL);
> +
> + /* write the seed */
> + for (i = 0; i < SS_SEED_LEN / 4; i++)
> + writel(ss->seed[i], ss->base + SS_KEY0 + i * 4);
> + writel(mode | SS_PRNG_START, ss->base + SS_CTL);
> +
> + /* Read the random data */
> + readsl(ss->base + SS_TXFIFO, data, len / 4);
> +
> + if (len % 4 > 0) {
> + v = readl(ss->base + SS_TXFIFO);
> + memcpy(data + len / 4, &v, len % 4);
> + }
hwrng core asks for "rng_buffer_size()" of data which is a multiple of
4. So len % 4 will be 0. I think the above check is not required. Feel
free to correct if I am wrong.
> + /* Update the seed */
> + for (i = 0; i < SS_SEED_LEN / 4; i++) {
> + v = readl(ss->base + SS_KEY0 + i * 4);
> + ss->seed[i] = v;
> + }
> +
> + writel(0, ss->base + SS_CTL);
> + spin_unlock_bh(&ss->slock);
> + return len;
> +}
> +
> +int sun4i_ss_hwrng_register(struct hwrng *hwrng)
> +{
> + hwrng->name = "sun4i Security System PRNG";
> + hwrng->init = sun4i_ss_hwrng_init;
> + hwrng->read = sun4i_ss_hwrng_read;
> + hwrng->quality = 1000;
> +
> + /* Cannot use devm_hwrng_register() since we need to hwrng_unregister
> + * before stopping clocks/regulator
> + */
> + return hwrng_register(hwrng);
> +}
> +
> +void sun4i_ss_hwrng_remove(struct hwrng *hwrng)
> +{
> + hwrng_unregister(hwrng);
> +}
> diff --git a/drivers/crypto/sunxi-ss/sun4i-ss.h b/drivers/crypto/sunxi-ss/sun4i-ss.h
> index f04c0f8..1297510 100644
> --- a/drivers/crypto/sunxi-ss/sun4i-ss.h
> +++ b/drivers/crypto/sunxi-ss/sun4i-ss.h
> @@ -23,6 +23,7 @@
> #include <linux/scatterlist.h>
> #include <linux/interrupt.h>
> #include <linux/delay.h>
> +#include <linux/hw_random.h>
> #include <crypto/md5.h>
> #include <crypto/sha.h>
> #include <crypto/hash.h>
> @@ -125,6 +126,9 @@
> #define SS_RXFIFO_EMP_INT_ENABLE (1 << 2)
> #define SS_TXFIFO_AVA_INT_ENABLE (1 << 0)
>
> +#define SS_SEED_LEN (192 / 8)
> +#define SS_DATA_LEN (160 / 8)
> +
> struct sun4i_ss_ctx {
> void __iomem *base;
> int irq;
> @@ -134,6 +138,8 @@ struct sun4i_ss_ctx {
> struct device *dev;
> struct resource *res;
> spinlock_t slock; /* control the use of the device */
> + struct hwrng hwrng;
> + u32 seed[SS_SEED_LEN / 4];
> };
>
> struct sun4i_ss_alg_template {
> @@ -199,3 +205,5 @@ int sun4i_ss_des_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
> unsigned int keylen);
> int sun4i_ss_des3_setkey(struct crypto_ablkcipher *tfm, const u8 *key,
> unsigned int keylen);
> +int sun4i_ss_hwrng_register(struct hwrng *hwrng);
> +void sun4i_ss_hwrng_remove(struct hwrng *hwrng);
> --
> 2.7.3
>
> --
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