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

[Max Resch]

Hi there Marek,

Am 05/02/2024 um 12.40 schrieb Marek Behún:
> Hello Max,
> 
> Out of curiousity, what is your use case for having these random
> numbers on this platform in U-Boot?

I use 2 EspressoBin (Armada 3720) as routers, both of them use the 
TurrisMox firmware. RNG enables the EFI RNG protocol which inturn allows 
systemd-boot to populate the Linux RNG EFI seed config table which 
enables ealy initialization of the kernel prng.
The kernel also then allows the use of KASLR. When the kernel is booted 
up a module is available to interface with the Firmware to use the RNG 
directly.

Also, I'm not sure if this should be part of the patch, this could be 
enabled on some default configurations for the Armada 3700.

-- Max

> 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