[PATCH v5 3/8] stm32mp1: rng: Add a driver for random number generator(rng) device

[Sughosh Ganu]

On Fri, 27 Dec 2019 at 18:12, Heinrich Schuchardt <xypron.glpk at gmx.de>
wrote:

> On 12/27/19 12:19 PM, Sughosh Ganu wrote:
> >
> > On Fri, 27 Dec 2019 at 13:21, Heinrich Schuchardt <xypron.glpk at gmx.de
> > <mailto:xypron.glpk at gmx.de>> wrote:
> >
> >     On 12/26/19 6:25 PM, Sughosh Ganu wrote:
> >      > Add a driver for the rng device found on stm32mp1 platforms. The
> >      > driver provides a routine for reading the random number seed from
> the
> >      > hardware device.
> >      >
> >      > Signed-off-by: Sughosh Ganu <sughosh.ganu at linaro.org
> >     <mailto:sughosh.ganu at linaro.org>>
> >      > Reviewed-by: Patrice Chotard <patrice.chotard at st.com
> >     <mailto:patrice.chotard at st.com>>
> >      > Acked-by: Patrick Delaunay <patrick.delaunay at st.com
> >     <mailto:patrick.delaunay at st.com>>
> >      > ---
> >      > Changes since V4:
> >      > * Return number of bytes read on a successful read, and a -ve
> >     value on
> >      >    error.
> >      >
> >      >   drivers/rng/Kconfig        |   7 ++
> >      >   drivers/rng/Makefile       |   1 +
> >      >   drivers/rng/stm32mp1_rng.c | 165
> >     +++++++++++++++++++++++++++++++++++++++++++++
> >      >   3 files changed, 173 insertions(+)
> >      >   create mode 100644 drivers/rng/stm32mp1_rng.c
> >      >
> >      > diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> >      > index dd44cc0..c9c4751 100644
> >      > --- a/drivers/rng/Kconfig
> >      > +++ b/drivers/rng/Kconfig
> >      > @@ -5,3 +5,10 @@ config DM_RNG
> >      >         Enable driver model for random number generator(rng)
> devices.
> >      >         This interface is used to initialise the rng device and to
> >      >         read the random seed from the device.
> >      > +
> >      > +config RNG_STM32MP1
> >      > +     bool "Enable random number generator for STM32MP1"
> >      > +     depends on ARCH_STM32MP && DM_RNG
> >      > +     default n
> >      > +     help
> >      > +       Enable STM32MP1 rng driver.
> >      > diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> >      > index 311705b..699beb3 100644
> >      > --- a/drivers/rng/Makefile
> >      > +++ b/drivers/rng/Makefile
> >      > @@ -4,3 +4,4 @@
> >      >   #
> >      >
> >      >   obj-$(CONFIG_DM_RNG) += rng-uclass.o
> >      > +obj-$(CONFIG_RNG_STM32MP1) += stm32mp1_rng.o
> >      > diff --git a/drivers/rng/stm32mp1_rng.c
> b/drivers/rng/stm32mp1_rng.c
> >      > new file mode 100644
> >      > index 0000000..56ad848
> >      > --- /dev/null
> >      > +++ b/drivers/rng/stm32mp1_rng.c
> >      > @@ -0,0 +1,165 @@
> >      > +// SPDX-License-Identifier: GPL-2.0-or-later
> >      > +/*
> >      > + * Copyright (c) 2019, Linaro Limited
> >      > + */
> >      > +
> >      > +#include <common.h>
> >      > +#include <clk.h>
> >      > +#include <dm.h>
> >      > +#include <reset.h>
> >      > +#include <rng.h>
> >      > +
> >      > +#include <asm/io.h>
> >      > +#include <linux/iopoll.h>
> >      > +#include <linux/kernel.h>
> >      > +
> >      > +#define RNG_CR 0x00
> >      > +#define RNG_CR_RNGEN BIT(2)
> >      > +#define RNG_CR_CED BIT(5)
> >      > +
> >      > +#define RNG_SR 0x04
> >      > +#define RNG_SR_SEIS BIT(6)
> >      > +#define RNG_SR_CEIS BIT(5)
> >      > +#define RNG_SR_SECS BIT(2)
> >      > +#define RNG_SR_DRDY BIT(0)
> >      > +
> >      > +#define RNG_DR 0x08
> >      > +
> >      > +struct stm32_rng_platdata {
> >      > +     fdt_addr_t base;
> >      > +     struct clk clk;
> >      > +     struct reset_ctl rst;
> >      > +};
> >      > +
> >      > +static int stm32_rng_read(struct udevice *dev, void *data,
> >     size_t len)
> >      > +{
> >      > +     int retval = 0, i, nbytes;
> >      > +     u32 sr, count, reg;
> >      > +     size_t increment;
> >      > +     struct stm32_rng_platdata *pdata = dev_get_platdata(dev);
> >      > +
> >      > +     /*
> >      > +      * Only INT_MAX number of bytes can be returned. If more
> >      > +      * bytes need to be read, the caller must do it in a loop.
> >      > +      */
> >      > +     if (len > INT_MAX)
> >      > +             len = INT_MAX;
> >      > +
> >      > +     nbytes = len;
> >      > +     while (len > 0) {
> >      > +             retval = readl_poll_timeout(pdata->base + RNG_SR,
> sr,
> >      > +                                         sr & RNG_SR_DRDY,
> 10000);
> >      > +             if (retval)
> >      > +                     return retval;
> >      > +
> >      > +             if (sr & (RNG_SR_SEIS | RNG_SR_SECS)) {
> >      > +                     /* As per SoC TRM */
> >      > +                     clrbits_le32(pdata->base + RNG_SR,
> >     RNG_SR_SEIS);
> >      > +                     for (i = 0; i < 12; i++)
> >      > +                             readl(pdata->base + RNG_DR);
> >      > +                     if (readl(pdata->base + RNG_SR) &
> >     RNG_SR_SEIS) {
> >      > +                             printf("RNG Noise");
> >      > +                             return -EIO;
> >
> >     The SEIS bit indicates a seed error. According to the RM0090
> Reference
> >     manual for the STM32F429/439 you should clear the SEIS bit and set
> the
> >     RNGEN bit to restart the RNG.
> >
> >
> https://www.st.com/content/ccc/resource/technical/document/reference_manual/3d/6d/5a/66/b4/99/40/d4/DM00031020.pdf/files/DM00031020.pdf/jcr:content/translations/en.DM00031020.pdf
> ,
> >     page 768.
> >
> >     So why do you return an error code here? What do you expect the
> caller
> >     to do?
> >
> >
> > I am referring to the stm32mp157 trm, Noise source error detection, pg
> 1939.
>
> Could you, please, provide a link to the document for stm32mp157.
>

I was required to create a login to wiki.st.com to get access to the
document. Don't think there is a link for the document available.

-sughosh