[PATCH v2] rng: Add Turris Mox rWTM RNG driver

[Mark Kettenis]

> Date: Mon, 5 Feb 2024 12:40:14 +0100
> From: Marek Behún <kabel at kernel.org>
> 
> Hello Max,
> 
> Out of curiousity, what is your use case for having these random
> numbers on this platform in U-Boot?

It means that U-Boot will implement the EFI RNG protocol.  The OpenBSD
bootloader will use that to fill an initial pool of random numbers for
the kernel.  And the Linux kernel EFI stub uses it to do kernel
address space randomization.

Cheers,

Mark

> Below are a few more things to change and then you I'll give my
> Reviewed-by tag.
> 
> On Sun, 21 Jan 2024 21:17:16 +0100
> Max Resch <resch.max at gmail.com> wrote:
> 
> > A RNG driver for Armada 3720 boards running the Turris Mox rWTM firmware
> > from CZ.NIC in the secure processor.
> > 
> > Signed-off-by: Max Resch <resch.max at gmail.com>
> > ---
> > 
> > Changes in v2:
> >  - Removed ring buffer implementation
> > 
> >  drivers/rng/Kconfig           |   8 +++
> >  drivers/rng/Makefile          |   1 +
> >  drivers/rng/turris_rwtm_rng.c | 122 ++++++++++++++++++++++++++++++++++
> >  3 files changed, 131 insertions(+)
> >  create mode 100644 drivers/rng/turris_rwtm_rng.c
> > 
> > diff --git a/drivers/rng/Kconfig b/drivers/rng/Kconfig
> > index a89c899568..cd72852a47 100644
> > --- a/drivers/rng/Kconfig
> > +++ b/drivers/rng/Kconfig
> > @@ -105,4 +105,12 @@ config RNG_JH7110
> >  	help
> >  	  Enable True Random Number Generator in StarFive JH7110 SoCs.
> >  
> > +config RNG_TURRIS_RWTM
> > +	bool "Turris Mox TRNG in Secure Processor"
> > +	depends on DM_RNG && ARMADA_3700
> > +	help
> > +	  Use TRNG in Turris Mox Secure Processor Firmware. Can be used
> > +	  on other Armada-3700 devices (like EspressoBin) if Secure
> > +	  Firmware from CZ.NIC is used.
> > +
> >  endif
> > diff --git a/drivers/rng/Makefile b/drivers/rng/Makefile
> > index 7e64c4cdfc..ecae1a3da3 100644
> > --- a/drivers/rng/Makefile
> > +++ b/drivers/rng/Makefile
> > @@ -17,3 +17,4 @@ obj-$(CONFIG_RNG_SMCCC_TRNG) += smccc_trng.o
> >  obj-$(CONFIG_RNG_ARM_RNDR) += arm_rndr.o
> >  obj-$(CONFIG_TPM_RNG) += tpm_rng.o
> >  obj-$(CONFIG_RNG_JH7110) += jh7110_rng.o
> > +obj-$(CONFIG_RNG_TURRIS_RWTM) += turris_rwtm_rng.o
> > diff --git a/drivers/rng/turris_rwtm_rng.c b/drivers/rng/turris_rwtm_rng.c
> > new file mode 100644
> > index 0000000000..143fe0b47f
> > --- /dev/null
> > +++ b/drivers/rng/turris_rwtm_rng.c
> > @@ -0,0 +1,122 @@
> > +// SPDX-License-Identifier: GPL-2.0-or-later OR BSD-3-Clause
> > +/*
> > + * Copyright (c) 2024, Max Resch
> > + */
> > +
> > +#include <dm.h>
> > +#include <malloc.h>
> > +#include <rng.h>
> > +#include <asm/dma-mapping.h>
> > +#include <asm/types.h>
> > +#include <mach/mbox.h>
> > +
> > +/* size of entropy buffer */
> > +#define RNG_BUFFER_SIZE	128U
> > +
> > +struct turris_rwtm_rng_priv {
> > +	phys_addr_t buffer;
> > +};
> > +
> > +static int turris_rwtm_rng_fill_entropy(phys_addr_t entropy, size_t size)
> > +{
> > +	u32 args[3] = { 1, (u32)entropy, size };
> > +	int ret;
> > +
> > +	/* flush data cache */
> > +	flush_dcache_range(entropy, entropy + size);
> > +
> > +	/*
> > +	 * get entropy
> > +	 * args[0] = 1 copies BYTES array in args[1] of length args[2]
> > +	 */
> > +	ret = mbox_do_cmd(MBOX_CMD_GET_RANDOM, args, 3, NULL, 0);
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* invalidate data cache */
> > +	invalidate_dcache_range(entropy, entropy + size);
> > +
> > +	return 0;
> > +}
> > +
> > +static int turris_rwtm_rng_random_read(struct udevice *dev, void *data, size_t count)
> > +{
> > +	phys_addr_t p;
> > +	size_t size;
> > +	int ret;
> > +
> > +	p = ((struct turris_rwtm_rng_priv *)dev_get_priv(dev))->buffer;
> 
> Please declare
> 
>   struct turris_rwtm_rng_priv *priv = dev_get_priv(dev);
>   phys_addr_t phys;
>   size_t size;
>   int ret;
> 
> and then do 
> 
>   phys = priv->buffer;
> 
> > +	while (count) {
> > +		size = min_t(size_t, RNG_BUFFER_SIZE, count);
> > +
> > +		ret = turris_rwtm_rng_fill_entropy(p, size);
> > +
> > +		memcpy(data, (void *)p, size);
> > +		count -= size;
> > +		data = (u8 *)data + size;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +static int turris_rwtm_rng_probe(struct udevice *dev)
> > +{
> > +	struct turris_rwtm_rng_priv *priv;
> 
>   = dev_get_priv(dev);
> 
> > +	u32 args[] = { 0 };
> > +	int ret;
> > +
> > +	/*
> > +	 * check if the random command is supported
> > +	 * args[0] = 0 would copy 16 DWORDS entropy to out but we ignore them
> > +	 */
> > +	ret = mbox_do_cmd(MBOX_CMD_GET_RANDOM, args, ARRAY_SIZE(args), NULL, 0);
> > +
> > +	if (ret < 0)
> > +		return ret;
> > +
> > +	/* entropy buffer */
> > +	priv = (struct turris_rwtm_rng_priv *)dev_get_priv(dev);
> no need here, do it at the beginning
> 
> 
> > +	priv->buffer = 0;
> > +
> > +	/* buffer address need to be aligned */
> > +	dma_alloc_coherent(RNG_BUFFER_SIZE, (unsigned long *)&priv->buffer);
> > +	if (!priv->buffer)
> > +		return -ENOMEM;
> > +
> > +	return 0;
> > +}
> > +
> > +static int turris_rwtm_rng_remove(struct udevice *dev)
> > +{
> > +	phys_addr_t p;
> rename this to phys, and please do it as I described above.
> 
> > +
> > +	p = ((struct turris_rwtm_rng_priv *)dev_get_priv(dev))->buffer;
> > +	dma_free_coherent((void *)p);
> > +
> > +	return 0;
> 
> Marek
>