104 lines
2.6 KiB
C
104 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* CZ.NIC's Turris Omnia MCU TRNG driver
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*
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* 2024 by Marek Behún <kabel@kernel.org>
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*/
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#include <linux/bitfield.h>
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#include <linux/completion.h>
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#include <linux/container_of.h>
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#include <linux/errno.h>
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#include <linux/gpio/consumer.h>
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#include <linux/gpio/driver.h>
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#include <linux/hw_random.h>
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#include <linux/i2c.h>
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#include <linux/interrupt.h>
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#include <linux/minmax.h>
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#include <linux/string.h>
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#include <linux/types.h>
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#include <linux/turris-omnia-mcu-interface.h>
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#include "turris-omnia-mcu.h"
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#define OMNIA_CMD_TRNG_MAX_ENTROPY_LEN 64
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static irqreturn_t omnia_trng_irq_handler(int irq, void *dev_id)
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{
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struct omnia_mcu *mcu = dev_id;
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complete(&mcu->trng_entropy_ready);
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return IRQ_HANDLED;
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}
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static int omnia_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)
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{
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struct omnia_mcu *mcu = container_of(rng, struct omnia_mcu, trng);
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u8 reply[1 + OMNIA_CMD_TRNG_MAX_ENTROPY_LEN];
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int err, bytes;
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if (!wait && !completion_done(&mcu->trng_entropy_ready))
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return 0;
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do {
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if (wait_for_completion_interruptible(&mcu->trng_entropy_ready))
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return -ERESTARTSYS;
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err = omnia_cmd_read(mcu->client,
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OMNIA_CMD_TRNG_COLLECT_ENTROPY,
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reply, sizeof(reply));
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if (err)
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return err;
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bytes = min3(reply[0], max, OMNIA_CMD_TRNG_MAX_ENTROPY_LEN);
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} while (wait && !bytes);
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memcpy(data, &reply[1], bytes);
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return bytes;
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}
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int omnia_mcu_register_trng(struct omnia_mcu *mcu)
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{
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struct device *dev = &mcu->client->dev;
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u8 irq_idx, dummy;
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int irq, err;
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if (!(mcu->features & OMNIA_FEAT_TRNG))
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return 0;
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irq_idx = omnia_int_to_gpio_idx[__bf_shf(OMNIA_INT_TRNG)];
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irq = gpiod_to_irq(gpio_device_get_desc(mcu->gc.gpiodev, irq_idx));
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if (irq < 0)
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return dev_err_probe(dev, irq, "Cannot get TRNG IRQ\n");
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/*
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* If someone else cleared the TRNG interrupt but did not read the
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* entropy, a new interrupt won't be generated, and entropy collection
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* will be stuck. Ensure an interrupt will be generated by executing
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* the collect entropy command (and discarding the result).
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*/
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err = omnia_cmd_read(mcu->client, OMNIA_CMD_TRNG_COLLECT_ENTROPY,
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&dummy, 1);
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if (err)
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return err;
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init_completion(&mcu->trng_entropy_ready);
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err = devm_request_threaded_irq(dev, irq, NULL, omnia_trng_irq_handler,
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IRQF_ONESHOT, "turris-omnia-mcu-trng",
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mcu);
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if (err)
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return dev_err_probe(dev, err, "Cannot request TRNG IRQ\n");
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mcu->trng.name = "turris-omnia-mcu-trng";
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mcu->trng.read = omnia_trng_read;
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err = devm_hwrng_register(dev, &mcu->trng);
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if (err)
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return dev_err_probe(dev, err, "Cannot register TRNG\n");
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return 0;
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}
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