[4/6] hwrng: st: Add support for ST's HW Random Number Generator

Message ID 1442002110-28733-5-git-send-email-lee.jones@linaro.org
State Superseded
Headers show

Commit Message

Lee Jones Sept. 11, 2015, 8:08 p.m.
Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
---
 drivers/char/hw_random/Kconfig  |  10 +++
 drivers/char/hw_random/Makefile |   1 +
 drivers/char/hw_random/st-rng.c | 142 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 153 insertions(+)
 create mode 100644 drivers/char/hw_random/st-rng.c

Comments

Kieran Bingham Sept. 12, 2015, 10:58 p.m. | #1
Hi Lee,

On 11 September 2015 at 21:08, Lee Jones <lee.jones@linaro.org> wrote:
> Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
> Signed-off-by: Lee Jones <lee.jones@linaro.org>
> ---
>  drivers/char/hw_random/Kconfig  |  10 +++
>  drivers/char/hw_random/Makefile |   1 +
>  drivers/char/hw_random/st-rng.c | 142 ++++++++++++++++++++++++++++++++++++++++
>  3 files changed, 153 insertions(+)
>  create mode 100644 drivers/char/hw_random/st-rng.c
>
> diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
> index f48cf11..bb6cb77 100644
> --- a/drivers/char/hw_random/Kconfig
> +++ b/drivers/char/hw_random/Kconfig
> @@ -346,6 +346,16 @@ config HW_RANDOM_MSM
>
>           If unsure, say Y.
>
> +config HW_RANDOM_ST
> +       tristate "ST Microelectronics HW Random Number Generator support"
> +       depends on HW_RANDOM && ARCH_STI
> +       ---help---
> +         This driver provides kernel-side support for the Random Number
> +         Generator hardware found on STi series of SoCs.
> +
> +         To compile this driver as a module, choose M here: the
> +         module will be called st-rng.
> +
>  config HW_RANDOM_XGENE
>         tristate "APM X-Gene True Random Number Generator (TRNG) support"
>         depends on HW_RANDOM && ARCH_XGENE
> diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
> index 055bb01..8bcfb45 100644
> --- a/drivers/char/hw_random/Makefile
> +++ b/drivers/char/hw_random/Makefile
> @@ -30,4 +30,5 @@ obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
>  obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
>  obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
>  obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
> +obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
>  obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
> diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
> new file mode 100644
> index 0000000..717a831
> --- /dev/null
> +++ b/drivers/char/hw_random/st-rng.c
> @@ -0,0 +1,142 @@
> +/*
> + * ST Random Number Generator Driver ST's Platforms
> + *
> + * Author: Pankaj Dev: <pankaj.dev@st.com>
> + *         Lee Jones <lee.jones@linaro.org>
> + *
> + * Copyright (C) 2015 STMicroelectronics (R&D) Limited
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/delay.h>
> +#include <linux/hw_random.h>
> +#include <linux/io.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/platform_device.h>
> +#include <linux/slab.h>
> +
> +/* Registers */
> +#define ST_RNG_STATUS_REG              0x20
> +#define ST_RNG_DATA_REG                        0x24
> +
> +/* Registers fields */
> +#define ST_RNG_STATUS_BAD_SEQUENCE     BIT(0)
> +#define ST_RNG_STATUS_BAD_ALTERNANCE   BIT(1)
> +#define ST_RNG_STATUS_FIFO_FULL                BIT(5)
> +
> +#define ST_RNG_FIFO_SIZE               8
> +#define ST_RNG_SAMPLE_SIZE             2 /* 2 Byte (16bit) samples */
> +
> +/* Samples are available every 0.667us, which we round to 1us */
> +#define ST_RNG_FILL_FIFO_TIMEOUT   (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
> +
> +struct st_rng_data {
> +       void __iomem    *base;
> +       struct clk      *clk;
> +       struct hwrng    ops;
> +};
> +
> +static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
> +{
> +       struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
> +       u32 status;
> +       int i;
> +
> +       if (max < sizeof(u16))
> +               return -EINVAL;
> +
> +       /* Wait until FIFO is full - max 4uS*/
> +       for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
> +               status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
> +               if (status & ST_RNG_STATUS_FIFO_FULL)
> +                       break;
> +               udelay(1);
> +       }
> +
> +       if (i == ST_RNG_FILL_FIFO_TIMEOUT)
> +               return 0;
> +
> +       for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
> +               *(u16 *)(data + i) =
> +                       readl_relaxed(ddata->base + ST_RNG_DATA_REG);

Will this code always be called with max % 2 == 0? ...
 I.e. will
    st_rng_read(rng, data[5], 5, waitflg)
 overflow an array?


> +
> +       return i - 2;   /* No of bytes read */

  Really? Doesn't this return 0 on st_rng_read(rng, data[2], 2, waitflg);

> +}
> +
> +static int st_rng_probe(struct platform_device *pdev)
> +{
> +       struct st_rng_data *ddata;
> +       struct resource *res;
> +       struct clk *clk;
> +       void __iomem *base;
> +       int ret;
> +
> +       ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
> +       if (!ddata)
> +               return -ENOMEM;
> +
> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       base = devm_ioremap_resource(&pdev->dev, res);
> +       if (IS_ERR(base))

Are we leaking ddata here ? I.e. before its attached with set_drvdata?

> +               return PTR_ERR(base);
> +
> +       clk = devm_clk_get(&pdev->dev, NULL);
> +       if (!clk)

And here ...

> +               return -EINVAL;
> +
> +       clk_prepare_enable(clk);
> +
> +       ddata->ops.priv = (unsigned long)ddata;
> +       ddata->ops.read = st_rng_read;
> +       ddata->ops.name = pdev->name;
> +       ddata->base     = base;
> +       ddata->clk      = clk;
> +
> +       dev_set_drvdata(&pdev->dev, ddata);
> +
> +       ret = hwrng_register(&ddata->ops);
> +       if (ret) {
> +               dev_err(&pdev->dev, "Failed to register HW RNG\n");
> +               return ret;
> +       }
> +
> +       dev_info(&pdev->dev, "Successfully registered HW RNG\n");
> +
> +       return 0;
> +}
> +
> +static int st_rng_remove(struct platform_device *pdev)
> +{
> +       struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
> +
> +       hwrng_unregister(&ddata->ops);
> +
> +       clk_disable_unprepare(ddata->clk);
> +
> +       return 0;
> +}
> +
> +static const struct of_device_id st_rng_match[] = {
> +       { .compatible = "st,rng" },
> +       {},
> +};
> +MODULE_DEVICE_TABLE(of, st_rng_match);
> +
> +static struct platform_driver st_rng_driver = {
> +       .driver = {
> +               .name = "st-hwrandom",
> +               .of_match_table = of_match_ptr(st_rng_match),
> +       },
> +       .probe = st_rng_probe,
> +       .remove = st_rng_remove
> +};
> +
> +module_platform_driver(st_rng_driver);
> +
> +MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
> +MODULE_LICENSE("GPL v2");
> --
> 1.9.1
>
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--
Regards
Kieran

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Fabio Estevam Sept. 12, 2015, 11:04 p.m. | #2
On Fri, Sep 11, 2015 at 5:08 PM, Lee Jones <lee.jones@linaro.org> wrote:

> +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +       base = devm_ioremap_resource(&pdev->dev, res);
> +       if (IS_ERR(base))
> +               return PTR_ERR(base);
> +
> +       clk = devm_clk_get(&pdev->dev, NULL);
> +       if (!clk)
> +               return -EINVAL;

This should be:

    if (IS_ERR(clk))
        return PTR_ERR(clk);

> +
> +       clk_prepare_enable(clk);

This may fail, so better check its return value and propagate it on error.

> +
> +       ddata->ops.priv = (unsigned long)ddata;
> +       ddata->ops.read = st_rng_read;
> +       ddata->ops.name = pdev->name;
> +       ddata->base     = base;
> +       ddata->clk      = clk;
> +
> +       dev_set_drvdata(&pdev->dev, ddata);
> +
> +       ret = hwrng_register(&ddata->ops);
> +       if (ret) {
> +               dev_err(&pdev->dev, "Failed to register HW RNG\n");
> +               return ret;
> +       }
> +
> +       dev_info(&pdev->dev, "Successfully registered HW RNG\n");

No need to put this info.
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Lee Jones Sept. 14, 2015, 7:42 a.m. | #3
On Sat, 12 Sep 2015, Fabio Estevam wrote:

> On Fri, Sep 11, 2015 at 5:08 PM, Lee Jones <lee.jones@linaro.org> wrote:
> 
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       base = devm_ioremap_resource(&pdev->dev, res);
> > +       if (IS_ERR(base))
> > +               return PTR_ERR(base);
> > +
> > +       clk = devm_clk_get(&pdev->dev, NULL);
> > +       if (!clk)
> > +               return -EINVAL;
> 
> This should be:
> 
>     if (IS_ERR(clk))
>         return PTR_ERR(clk);

You're right.  Will fix.

> > +
> > +       clk_prepare_enable(clk);
> 
> This may fail, so better check its return value and propagate it on error.

Looks like the jury is out on this one.

$ git grep clk_prepare_enable | grep '= clk\|if (' | wc -l
659
$ git grep clk_prepare_enable | grep -v '= clk\|if (' | wc -l
569

... but it's not a problem to fix up.  Will do.

> > +       ddata->ops.priv = (unsigned long)ddata;
> > +       ddata->ops.read = st_rng_read;
> > +       ddata->ops.name = pdev->name;
> > +       ddata->base     = base;
> > +       ddata->clk      = clk;
> > +
> > +       dev_set_drvdata(&pdev->dev, ddata);
> > +
> > +       ret = hwrng_register(&ddata->ops);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "Failed to register HW RNG\n");
> > +               return ret;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "Successfully registered HW RNG\n");
> 
> No need to put this info.

Ah, you caught me!

I know these types of prints are usually deemed not useful; however,
unless there is a failure both this driver and the core driver are
silent, so the user doesn't know that 1 or more of these devices are
available.  I personally like to see an entry in the bootlog for this
kind of functionality.
Lee Jones Sept. 14, 2015, 8:04 a.m. | #4
On Sat, 12 Sep 2015, Kieran Bingham wrote:
> On 11 September 2015 at 21:08, Lee Jones <lee.jones@linaro.org> wrote:
> > Signed-off-by: Pankaj Dev <pankaj.dev@st.com>
> > Signed-off-by: Lee Jones <lee.jones@linaro.org>
> > ---
> >  drivers/char/hw_random/Kconfig  |  10 +++
> >  drivers/char/hw_random/Makefile |   1 +
> >  drivers/char/hw_random/st-rng.c | 142 ++++++++++++++++++++++++++++++++++++++++
> >  3 files changed, 153 insertions(+)
> >  create mode 100644 drivers/char/hw_random/st-rng.c
> >
> > diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
> > index f48cf11..bb6cb77 100644
> > --- a/drivers/char/hw_random/Kconfig
> > +++ b/drivers/char/hw_random/Kconfig
> > @@ -346,6 +346,16 @@ config HW_RANDOM_MSM
> >
> >           If unsure, say Y.
> >
> > +config HW_RANDOM_ST
> > +       tristate "ST Microelectronics HW Random Number Generator support"
> > +       depends on HW_RANDOM && ARCH_STI
> > +       ---help---
> > +         This driver provides kernel-side support for the Random Number
> > +         Generator hardware found on STi series of SoCs.
> > +
> > +         To compile this driver as a module, choose M here: the
> > +         module will be called st-rng.
> > +
> >  config HW_RANDOM_XGENE
> >         tristate "APM X-Gene True Random Number Generator (TRNG) support"
> >         depends on HW_RANDOM && ARCH_XGENE
> > diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
> > index 055bb01..8bcfb45 100644
> > --- a/drivers/char/hw_random/Makefile
> > +++ b/drivers/char/hw_random/Makefile
> > @@ -30,4 +30,5 @@ obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
> >  obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
> >  obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
> >  obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
> > +obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
> >  obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
> > diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
> > new file mode 100644
> > index 0000000..717a831
> > --- /dev/null
> > +++ b/drivers/char/hw_random/st-rng.c
> > @@ -0,0 +1,142 @@
> > +/*
> > + * ST Random Number Generator Driver ST's Platforms
> > + *
> > + * Author: Pankaj Dev: <pankaj.dev@st.com>
> > + *         Lee Jones <lee.jones@linaro.org>
> > + *
> > + * Copyright (C) 2015 STMicroelectronics (R&D) Limited
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +
> > +#include <linux/clk.h>
> > +#include <linux/delay.h>
> > +#include <linux/hw_random.h>
> > +#include <linux/io.h>
> > +#include <linux/module.h>
> > +#include <linux/of.h>
> > +#include <linux/platform_device.h>
> > +#include <linux/slab.h>
> > +
> > +/* Registers */
> > +#define ST_RNG_STATUS_REG              0x20
> > +#define ST_RNG_DATA_REG                        0x24
> > +
> > +/* Registers fields */
> > +#define ST_RNG_STATUS_BAD_SEQUENCE     BIT(0)
> > +#define ST_RNG_STATUS_BAD_ALTERNANCE   BIT(1)
> > +#define ST_RNG_STATUS_FIFO_FULL                BIT(5)
> > +
> > +#define ST_RNG_FIFO_SIZE               8
> > +#define ST_RNG_SAMPLE_SIZE             2 /* 2 Byte (16bit) samples */
> > +
> > +/* Samples are available every 0.667us, which we round to 1us */
> > +#define ST_RNG_FILL_FIFO_TIMEOUT   (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
> > +
> > +struct st_rng_data {
> > +       void __iomem    *base;
> > +       struct clk      *clk;
> > +       struct hwrng    ops;
> > +};
> > +
> > +static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
> > +{
> > +       struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
> > +       u32 status;
> > +       int i;
> > +
> > +       if (max < sizeof(u16))
> > +               return -EINVAL;
> > +
> > +       /* Wait until FIFO is full - max 4uS*/
> > +       for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
> > +               status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
> > +               if (status & ST_RNG_STATUS_FIFO_FULL)
> > +                       break;
> > +               udelay(1);
> > +       }
> > +
> > +       if (i == ST_RNG_FILL_FIFO_TIMEOUT)
> > +               return 0;
> > +
> > +       for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
> > +               *(u16 *)(data + i) =
> > +                       readl_relaxed(ddata->base + ST_RNG_DATA_REG);
> 
> Will this code always be called with max % 2 == 0? ...
>  I.e. will
>     st_rng_read(rng, data[5], 5, waitflg)
>  overflow an array?

.read() can be called with either 16, 32 or the size of the cache,
which is unlikely to be anything !(N^2) (it's 64 in our case).

> > +
> > +       return i - 2;   /* No of bytes read */
> 
>   Really? Doesn't this return 0 on st_rng_read(rng, data[2], 2, waitflg);

Hmm... I assumed the OA's math was good here.

Good spot.  I will run some tests to confirm.

> > +}
> > +
> > +static int st_rng_probe(struct platform_device *pdev)
> > +{
> > +       struct st_rng_data *ddata;
> > +       struct resource *res;
> > +       struct clk *clk;
> > +       void __iomem *base;
> > +       int ret;
> > +
> > +       ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
> > +       if (!ddata)
> > +               return -ENOMEM;
> > +
> > +       res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> > +       base = devm_ioremap_resource(&pdev->dev, res);
> > +       if (IS_ERR(base))
> 
> Are we leaking ddata here ? I.e. before its attached with set_drvdata?

It won't leak.  That's the point of devm_*.

Please see: Documentation/driver-model/devres.txt

> > +               return PTR_ERR(base);
> > +
> > +       clk = devm_clk_get(&pdev->dev, NULL);
> > +       if (!clk)
> 
> And here ...

Nope.

> > +               return -EINVAL;
> > +
> > +       clk_prepare_enable(clk);
> > +
> > +       ddata->ops.priv = (unsigned long)ddata;
> > +       ddata->ops.read = st_rng_read;
> > +       ddata->ops.name = pdev->name;
> > +       ddata->base     = base;
> > +       ddata->clk      = clk;
> > +
> > +       dev_set_drvdata(&pdev->dev, ddata);
> > +
> > +       ret = hwrng_register(&ddata->ops);
> > +       if (ret) {
> > +               dev_err(&pdev->dev, "Failed to register HW RNG\n");
> > +               return ret;
> > +       }
> > +
> > +       dev_info(&pdev->dev, "Successfully registered HW RNG\n");
> > +
> > +       return 0;
> > +}
> > +
> > +static int st_rng_remove(struct platform_device *pdev)
> > +{
> > +       struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
> > +
> > +       hwrng_unregister(&ddata->ops);
> > +
> > +       clk_disable_unprepare(ddata->clk);
> > +
> > +       return 0;
> > +}
> > +
> > +static const struct of_device_id st_rng_match[] = {
> > +       { .compatible = "st,rng" },
> > +       {},
> > +};
> > +MODULE_DEVICE_TABLE(of, st_rng_match);
> > +
> > +static struct platform_driver st_rng_driver = {
> > +       .driver = {
> > +               .name = "st-hwrandom",
> > +               .of_match_table = of_match_ptr(st_rng_match),
> > +       },
> > +       .probe = st_rng_probe,
> > +       .remove = st_rng_remove
> > +};
> > +
> > +module_platform_driver(st_rng_driver);
> > +
> > +MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
> > +MODULE_LICENSE("GPL v2");
> >
> 
>

Patch

diff --git a/drivers/char/hw_random/Kconfig b/drivers/char/hw_random/Kconfig
index f48cf11..bb6cb77 100644
--- a/drivers/char/hw_random/Kconfig
+++ b/drivers/char/hw_random/Kconfig
@@ -346,6 +346,16 @@  config HW_RANDOM_MSM
 
 	  If unsure, say Y.
 
+config HW_RANDOM_ST
+	tristate "ST Microelectronics HW Random Number Generator support"
+	depends on HW_RANDOM && ARCH_STI
+	---help---
+	  This driver provides kernel-side support for the Random Number
+	  Generator hardware found on STi series of SoCs.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called st-rng.
+
 config HW_RANDOM_XGENE
 	tristate "APM X-Gene True Random Number Generator (TRNG) support"
 	depends on HW_RANDOM && ARCH_XGENE
diff --git a/drivers/char/hw_random/Makefile b/drivers/char/hw_random/Makefile
index 055bb01..8bcfb45 100644
--- a/drivers/char/hw_random/Makefile
+++ b/drivers/char/hw_random/Makefile
@@ -30,4 +30,5 @@  obj-$(CONFIG_HW_RANDOM_TPM) += tpm-rng.o
 obj-$(CONFIG_HW_RANDOM_BCM2835) += bcm2835-rng.o
 obj-$(CONFIG_HW_RANDOM_IPROC_RNG200) += iproc-rng200.o
 obj-$(CONFIG_HW_RANDOM_MSM) += msm-rng.o
+obj-$(CONFIG_HW_RANDOM_ST) += st-rng.o
 obj-$(CONFIG_HW_RANDOM_XGENE) += xgene-rng.o
diff --git a/drivers/char/hw_random/st-rng.c b/drivers/char/hw_random/st-rng.c
new file mode 100644
index 0000000..717a831
--- /dev/null
+++ b/drivers/char/hw_random/st-rng.c
@@ -0,0 +1,142 @@ 
+/*
+ * ST Random Number Generator Driver ST's Platforms
+ *
+ * Author: Pankaj Dev: <pankaj.dev@st.com>
+ *         Lee Jones <lee.jones@linaro.org>
+ *
+ * Copyright (C) 2015 STMicroelectronics (R&D) Limited
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/hw_random.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/platform_device.h>
+#include <linux/slab.h>
+
+/* Registers */
+#define ST_RNG_STATUS_REG		0x20
+#define ST_RNG_DATA_REG			0x24
+
+/* Registers fields */
+#define ST_RNG_STATUS_BAD_SEQUENCE	BIT(0)
+#define ST_RNG_STATUS_BAD_ALTERNANCE	BIT(1)
+#define ST_RNG_STATUS_FIFO_FULL		BIT(5)
+
+#define ST_RNG_FIFO_SIZE		8
+#define ST_RNG_SAMPLE_SIZE		2 /* 2 Byte (16bit) samples */
+
+/* Samples are available every 0.667us, which we round to 1us */
+#define ST_RNG_FILL_FIFO_TIMEOUT   (1 * (ST_RNG_FIFO_SIZE / ST_RNG_SAMPLE_SIZE))
+
+struct st_rng_data {
+	void __iomem	*base;
+	struct clk	*clk;
+	struct hwrng	ops;
+};
+
+static int st_rng_read(struct hwrng *rng, void *data, size_t max, bool wait)
+{
+	struct st_rng_data *ddata = (struct st_rng_data *)rng->priv;
+	u32 status;
+	int i;
+
+	if (max < sizeof(u16))
+		return -EINVAL;
+
+	/* Wait until FIFO is full - max 4uS*/
+	for (i = 0; i < ST_RNG_FILL_FIFO_TIMEOUT; i++) {
+		status = readl_relaxed(ddata->base + ST_RNG_STATUS_REG);
+		if (status & ST_RNG_STATUS_FIFO_FULL)
+			break;
+		udelay(1);
+	}
+
+	if (i == ST_RNG_FILL_FIFO_TIMEOUT)
+		return 0;
+
+	for (i = 0; i < ST_RNG_FIFO_SIZE && i < max; i += 2)
+		*(u16 *)(data + i) =
+			readl_relaxed(ddata->base + ST_RNG_DATA_REG);
+
+	return i - 2;	/* No of bytes read */
+}
+
+static int st_rng_probe(struct platform_device *pdev)
+{
+	struct st_rng_data *ddata;
+	struct resource *res;
+	struct clk *clk;
+	void __iomem *base;
+	int ret;
+
+	ddata = devm_kzalloc(&pdev->dev, sizeof(*ddata), GFP_KERNEL);
+	if (!ddata)
+		return -ENOMEM;
+
+	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+	base = devm_ioremap_resource(&pdev->dev, res);
+	if (IS_ERR(base))
+		return PTR_ERR(base);
+
+	clk = devm_clk_get(&pdev->dev, NULL);
+	if (!clk)
+		return -EINVAL;
+
+	clk_prepare_enable(clk);
+
+	ddata->ops.priv	= (unsigned long)ddata;
+	ddata->ops.read	= st_rng_read;
+	ddata->ops.name	= pdev->name;
+	ddata->base	= base;
+	ddata->clk	= clk;
+
+	dev_set_drvdata(&pdev->dev, ddata);
+
+	ret = hwrng_register(&ddata->ops);
+	if (ret) {
+		dev_err(&pdev->dev, "Failed to register HW RNG\n");
+		return ret;
+	}
+
+	dev_info(&pdev->dev, "Successfully registered HW RNG\n");
+
+	return 0;
+}
+
+static int st_rng_remove(struct platform_device *pdev)
+{
+	struct st_rng_data *ddata = dev_get_drvdata(&pdev->dev);
+
+	hwrng_unregister(&ddata->ops);
+
+	clk_disable_unprepare(ddata->clk);
+
+	return 0;
+}
+
+static const struct of_device_id st_rng_match[] = {
+	{ .compatible = "st,rng" },
+	{},
+};
+MODULE_DEVICE_TABLE(of, st_rng_match);
+
+static struct platform_driver st_rng_driver = {
+	.driver = {
+		.name = "st-hwrandom",
+		.of_match_table = of_match_ptr(st_rng_match),
+	},
+	.probe = st_rng_probe,
+	.remove = st_rng_remove
+};
+
+module_platform_driver(st_rng_driver);
+
+MODULE_AUTHOR("Pankaj Dev <pankaj.dev@st.com>");
+MODULE_LICENSE("GPL v2");