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1// SPDX-License-Identifier: GPL-2.02/*3 * CZ.NIC's Turris Omnia MCU TRNG driver4 *5 * 2024 by Marek Behún <kabel@kernel.org>6 */7 8#include <linux/bitfield.h>9#include <linux/completion.h>10#include <linux/container_of.h>11#include <linux/errno.h>12#include <linux/gpio/consumer.h>13#include <linux/gpio/driver.h>14#include <linux/hw_random.h>15#include <linux/i2c.h>16#include <linux/interrupt.h>17#include <linux/minmax.h>18#include <linux/string.h>19#include <linux/types.h>20 21#include <linux/turris-omnia-mcu-interface.h>22#include "turris-omnia-mcu.h"23 24#define OMNIA_CMD_TRNG_MAX_ENTROPY_LEN 6425 26static irqreturn_t omnia_trng_irq_handler(int irq, void *dev_id)27{28 struct omnia_mcu *mcu = dev_id;29 30 complete(&mcu->trng_entropy_ready);31 32 return IRQ_HANDLED;33}34 35static int omnia_trng_read(struct hwrng *rng, void *data, size_t max, bool wait)36{37 struct omnia_mcu *mcu = container_of(rng, struct omnia_mcu, trng);38 u8 reply[1 + OMNIA_CMD_TRNG_MAX_ENTROPY_LEN];39 int err, bytes;40 41 if (!wait && !completion_done(&mcu->trng_entropy_ready))42 return 0;43 44 do {45 if (wait_for_completion_interruptible(&mcu->trng_entropy_ready))46 return -ERESTARTSYS;47 48 err = omnia_cmd_read(mcu->client,49 OMNIA_CMD_TRNG_COLLECT_ENTROPY,50 reply, sizeof(reply));51 if (err)52 return err;53 54 bytes = min3(reply[0], max, OMNIA_CMD_TRNG_MAX_ENTROPY_LEN);55 } while (wait && !bytes);56 57 memcpy(data, &reply[1], bytes);58 59 return bytes;60}61 62int omnia_mcu_register_trng(struct omnia_mcu *mcu)63{64 struct device *dev = &mcu->client->dev;65 u8 irq_idx, dummy;66 int irq, err;67 68 if (!(mcu->features & OMNIA_FEAT_TRNG))69 return 0;70 71 irq_idx = omnia_int_to_gpio_idx[__bf_shf(OMNIA_INT_TRNG)];72 irq = gpiod_to_irq(gpio_device_get_desc(mcu->gc.gpiodev, irq_idx));73 if (irq < 0)74 return dev_err_probe(dev, irq, "Cannot get TRNG IRQ\n");75 76 /*77 * If someone else cleared the TRNG interrupt but did not read the78 * entropy, a new interrupt won't be generated, and entropy collection79 * will be stuck. Ensure an interrupt will be generated by executing80 * the collect entropy command (and discarding the result).81 */82 err = omnia_cmd_read(mcu->client, OMNIA_CMD_TRNG_COLLECT_ENTROPY,83 &dummy, 1);84 if (err)85 return err;86 87 init_completion(&mcu->trng_entropy_ready);88 89 err = devm_request_threaded_irq(dev, irq, NULL, omnia_trng_irq_handler,90 IRQF_ONESHOT, "turris-omnia-mcu-trng",91 mcu);92 if (err)93 return dev_err_probe(dev, err, "Cannot request TRNG IRQ\n");94 95 mcu->trng.name = "turris-omnia-mcu-trng";96 mcu->trng.read = omnia_trng_read;97 98 err = devm_hwrng_register(dev, &mcu->trng);99 if (err)100 return dev_err_probe(dev, err, "Cannot register TRNG\n");101 102 return 0;103}104