Unverified Commit 41bb142a authored by Marek Behún's avatar Marek Behún Committed by Arnd Bergmann
Browse files

platform: cznic: turris-omnia-mcu: Add support for MCU provided TRNG 



Add support for true random number generator provided by the MCU.
New Omnia boards come without the Atmel SHA204-A chip. Instead the
crypto functionality is provided by new microcontroller, which has
a TRNG peripheral.

Signed-off-by: default avatarMarek Behún <kabel@kernel.org>
Acked-by: default avatarBartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20240701113010.16447-7-kabel@kernel.org


Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
parent ab89fb5f

drivers/platform/cznic/Kconfig

+2 −0
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ config TURRIS_OMNIA_MCU 
	depends on I2C

	select GPIOLIB

	select GPIOLIB_IRQCHIP

	select HW_RANDOM

	select RTC_CLASS

	select WATCHDOG_CORE

	help
@@ -27,6 +28,7 @@ config TURRIS_OMNIA_MCU 
	  - board poweroff into true low power mode (with voltage regulators

	    disabled) and the ability to configure wake up from this mode (via

	    rtcwake)

	  - true random number generator (if available on the MCU)

	  - MCU watchdog

	  - GPIO pins

	    - to get front button press events (the front button can be

drivers/platform/cznic/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -4,4 +4,5 @@ obj-$(CONFIG_TURRIS_OMNIA_MCU) += turris-omnia-mcu.o 
turris-omnia-mcu-y		:= turris-omnia-mcu-base.o

turris-omnia-mcu-y		+= turris-omnia-mcu-gpio.o

turris-omnia-mcu-y		+= turris-omnia-mcu-sys-off-wakeup.o

turris-omnia-mcu-y		+= turris-omnia-mcu-trng.o

turris-omnia-mcu-y		+= turris-omnia-mcu-watchdog.o

drivers/platform/cznic/turris-omnia-mcu-base.c

+5 −1
Original line number Diff line number Diff line
@@ -381,7 +381,11 @@ static int omnia_mcu_probe(struct i2c_client *client) 
	if (err)

		return err;



	return omnia_mcu_register_gpiochip(mcu);

	err = omnia_mcu_register_gpiochip(mcu);

	if (err)

		return err;



	return omnia_mcu_register_trng(mcu);

}



static const struct of_device_id of_omnia_mcu_match[] = {

drivers/platform/cznic/turris-omnia-mcu-gpio.c

+1 −1
Original line number Diff line number Diff line
@@ -195,7 +195,7 @@ static const struct omnia_gpio omnia_gpios[64] = { 
};



/* mapping from interrupts to indexes of GPIOs in the omnia_gpios array */

static const u8 omnia_int_to_gpio_idx[32] = {

const u8 omnia_int_to_gpio_idx[32] = {

	[__bf_shf(OMNIA_INT_CARD_DET)]			= 4,

	[__bf_shf(OMNIA_INT_MSATA_IND)]			= 5,

	[__bf_shf(OMNIA_INT_USB30_OVC)]			= 6,

drivers/platform/cznic/turris-omnia-mcu-trng.c

0 → 100644
+103 −0
Original line number Diff line number Diff line 
// SPDX-License-Identifier: GPL-2.0

/*

 * CZ.NIC's Turris Omnia MCU TRNG driver

 *

 * 2024 by Marek Behún <kabel@kernel.org>

 */



#include <linux/bitfield.h>

#include <linux/completion.h>

#include <linux/container_of.h>

#include <linux/errno.h>

#include <linux/gpio/consumer.h>

#include <linux/gpio/driver.h>

#include <linux/hw_random.h>

#include <linux/i2c.h>

#include <linux/interrupt.h>

#include <linux/minmax.h>

#include <linux/string.h>

#include <linux/types.h>



#include <linux/turris-omnia-mcu-interface.h>

#include "turris-omnia-mcu.h"



#define OMNIA_CMD_TRNG_MAX_ENTROPY_LEN	64



static irqreturn_t omnia_trng_irq_handler(int irq, void *dev_id)

{

	struct omnia_mcu *mcu = dev_id;



	complete(&mcu->trng_entropy_ready);



	return IRQ_HANDLED;

}



static int omnia_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)

{

	struct omnia_mcu *mcu = container_of(rng, struct omnia_mcu, trng);

	u8 reply[1 + OMNIA_CMD_TRNG_MAX_ENTROPY_LEN];

	int err, bytes;



	if (!wait && !completion_done(&mcu->trng_entropy_ready))

		return 0;



	do {

		if (wait_for_completion_interruptible(&mcu->trng_entropy_ready))

			return -ERESTARTSYS;



		err = omnia_cmd_read(mcu->client,

				     OMNIA_CMD_TRNG_COLLECT_ENTROPY,

				     reply, sizeof(reply));

		if (err)

			return err;



		bytes = min3(reply[0], max, OMNIA_CMD_TRNG_MAX_ENTROPY_LEN);

	} while (wait && !bytes);



	memcpy(data, &reply[1], bytes);



	return bytes;

}



int omnia_mcu_register_trng(struct omnia_mcu *mcu)

{

	struct device *dev = &mcu->client->dev;

	u8 irq_idx, dummy;

	int irq, err;



	if (!(mcu->features & OMNIA_FEAT_TRNG))

		return 0;



	irq_idx = omnia_int_to_gpio_idx[__bf_shf(OMNIA_INT_TRNG)];

	irq = gpiod_to_irq(gpio_device_get_desc(mcu->gc.gpiodev, irq_idx));

	if (!irq)

		return dev_err_probe(dev, -ENXIO, "Cannot get TRNG IRQ\n");



	/*

	 * If someone else cleared the TRNG interrupt but did not read the

	 * entropy, a new interrupt won't be generated, and entropy collection

	 * will be stuck. Ensure an interrupt will be generated by executing

	 * the collect entropy command (and discarding the result).

	 */

	err = omnia_cmd_read(mcu->client, OMNIA_CMD_TRNG_COLLECT_ENTROPY,

			     &dummy, 1);

	if (err)

		return err;



	init_completion(&mcu->trng_entropy_ready);



	err = devm_request_threaded_irq(dev, irq, NULL, omnia_trng_irq_handler,

					IRQF_ONESHOT, "turris-omnia-mcu-trng",

					mcu);

	if (err)

		return dev_err_probe(dev, err, "Cannot request TRNG IRQ\n");



	mcu->trng.name = "turris-omnia-mcu-trng";

	mcu->trng.read = omnia_trng_read;



	err = devm_hwrng_register(dev, &mcu->trng);

	if (err)

		return dev_err_probe(dev, err, "Cannot register TRNG\n");



	return 0;

}