[PATCH v5 3/8] stm32mp1: rng: Add a driver for random number generator(rng) device
Sughosh Ganu
sughosh.ganu at linaro.org
Fri Dec 27 13:58:46 CET 2019
On Fri, 27 Dec 2019 at 18:25, Heinrich Schuchardt <xypron.glpk at gmx.de>
wrote:
> On 12/27/19 1:42 PM, Heinrich Schuchardt 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.
>
> RM0436 Reference manual STM32MP157 advanced Arm®-based 32-bit MPUs
>
>
> https://www.st.com/content/ccc/resource/technical/document/reference_manual/group0/51/ba/9e/5e/78/5b/4b/dd/DM00327659/files/DM00327659.pdf/jcr:content/translations/en.DM00327659.pdf
>
> chapter 37.3.7 - "Error management" requires the following error handling:
>
> 1. Clear the SEIS bit by writing it to “0”.
> 2. Read out 12 words from the RNG_DR register, and discard each of them
> in order to clean the pipeline.
> 3. Confirm that SEIS is still cleared. Random number generation is back
> to normal
>
> So the same error handling can be used for both SoCs.
>
Which is what the current logic is doing. In case, the SEIS bit is still
set after reading the 12 words, the driver returns an error, else it
continues.
-sughosh
More information about the U-Boot
mailing list