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

["Marek Behún" <kabel@kernel.org>]

So you're using A3720 with OpenBSD? Can I ask which A3720 boards do you
use?

Marek

On Mon, 05 Feb 2024 14:46:24 +0100
Mark Kettenis <mark.kettenis@xs4all.nl> wrote:

> > Date: Mon, 5 Feb 2024 12:40:14 +0100
> > From: Marek Behún <kabel@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@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@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
> >