// SPDX-License-Identifier: GPL-2.0
/*
 * TRNG driver for the StarFive JH7110 SoC
 *
 * Copyright (C) 2022 StarFive Technology Co.
 */

#include <linux/clk.h>
#include <linux/completion.h>
#include <linux/delay.h>
#include <linux/err.h>
#include <linux/hw_random.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/pm_runtime.h>
#include <linux/random.h>
#include <linux/reset.h>

/* trng register offset */
#define STARFIVE_CTRL			0x00
#define STARFIVE_STAT			0x04
#define STARFIVE_MODE			0x08
#define STARFIVE_SMODE			0x0C
#define STARFIVE_IE			0x10
#define STARFIVE_ISTAT			0x14
#define STARFIVE_RAND0			0x20
#define STARFIVE_RAND1			0x24
#define STARFIVE_RAND2			0x28
#define STARFIVE_RAND3			0x2C
#define STARFIVE_RAND4			0x30
#define STARFIVE_RAND5			0x34
#define STARFIVE_RAND6			0x38
#define STARFIVE_RAND7			0x3C
#define STARFIVE_AUTO_RQSTS		0x60
#define STARFIVE_AUTO_AGE		0x64

/* CTRL CMD */
#define STARFIVE_CTRL_EXEC_NOP		0x0
#define STARFIVE_CTRL_GENE_RANDNUM	0x1
#define STARFIVE_CTRL_EXEC_RANDRESEED	0x2

/* STAT */
#define STARFIVE_STAT_NONCE_MODE	BIT(2)
#define STARFIVE_STAT_R256		BIT(3)
#define STARFIVE_STAT_MISSION_MODE	BIT(8)
#define STARFIVE_STAT_SEEDED		BIT(9)
#define STARFIVE_STAT_LAST_RESEED(x)	((x) << 16)
#define STARFIVE_STAT_SRVC_RQST		BIT(27)
#define STARFIVE_STAT_RAND_GENERATING	BIT(30)
#define STARFIVE_STAT_RAND_SEEDING	BIT(31)

/* MODE */
#define STARFIVE_MODE_R256		BIT(3)

/* SMODE */
#define STARFIVE_SMODE_NONCE_MODE	BIT(2)
#define STARFIVE_SMODE_MISSION_MODE	BIT(8)
#define STARFIVE_SMODE_MAX_REJECTS(x)	((x) << 16)

/* IE */
#define STARFIVE_IE_RAND_RDY_EN		BIT(0)
#define STARFIVE_IE_SEED_DONE_EN	BIT(1)
#define STARFIVE_IE_LFSR_LOCKUP_EN	BIT(4)
#define STARFIVE_IE_GLBL_EN		BIT(31)

#define STARFIVE_IE_ALL			(STARFIVE_IE_GLBL_EN | \
					 STARFIVE_IE_RAND_RDY_EN | \
					 STARFIVE_IE_SEED_DONE_EN | \
					 STARFIVE_IE_LFSR_LOCKUP_EN)

/* ISTAT */
#define STARFIVE_ISTAT_RAND_RDY		BIT(0)
#define STARFIVE_ISTAT_SEED_DONE	BIT(1)
#define STARFIVE_ISTAT_LFSR_LOCKUP	BIT(4)

#define STARFIVE_RAND_LEN		sizeof(u32)

#define to_trng(p)			container_of(p, struct starfive_trng, rng)

enum reseed {
	RANDOM_RESEED,
	NONCE_RESEED,
};

enum mode {
	PRNG_128BIT,
	PRNG_256BIT,
};

struct starfive_trng {
	struct device		*dev;
	void __iomem		*base;
	struct clk		*hclk;
	struct clk		*ahb;
	struct reset_control	*rst;
	struct hwrng		rng;
	struct completion	random_done;
	struct completion	reseed_done;
	u32			mode;
	u32			mission;
	u32			reseed;
	/* protects against concurrent write to ctrl register */
	spinlock_t		write_lock;
};

static u16 autoreq;
module_param(autoreq, ushort, 0);
MODULE_PARM_DESC(autoreq, "Auto-reseeding after random number requests by host reaches specified counter:\n"
				" 0 - disable counter\n"
				" other - reload value for internal counter");

static u16 autoage;
module_param(autoage, ushort, 0);
MODULE_PARM_DESC(autoage, "Auto-reseeding after specified timer countdowns to 0:\n"
				" 0 - disable timer\n"
				" other - reload value for internal timer");

static inline int starfive_trng_wait_idle(struct starfive_trng *trng)
{
	u32 stat;

	return readl_relaxed_poll_timeout(trng->base + STARFIVE_STAT, stat,
					  !(stat & (STARFIVE_STAT_RAND_GENERATING |
						    STARFIVE_STAT_RAND_SEEDING)),
					  10, 100000);
}

static inline void starfive_trng_irq_mask_clear(struct starfive_trng *trng)
{
	/* clear register: ISTAT */
	u32 data = readl(trng->base + STARFIVE_ISTAT);

	writel(data, trng->base + STARFIVE_ISTAT);
}

static int starfive_trng_cmd(struct starfive_trng *trng, u32 cmd, bool wait)
{
	int wait_time = 1000;

	/* allow up to 40 us for wait == 0 */
	if (!wait)
		wait_time = 40;

	switch (cmd) {
	case STARFIVE_CTRL_GENE_RANDNUM:
		reinit_completion(&trng->random_done);
		spin_lock_irq(&trng->write_lock);
		writel(cmd, trng->base + STARFIVE_CTRL);
		spin_unlock_irq(&trng->write_lock);
		if (!wait_for_completion_timeout(&trng->random_done, usecs_to_jiffies(wait_time)))
			return -ETIMEDOUT;
		break;
	case STARFIVE_CTRL_EXEC_RANDRESEED:
		reinit_completion(&trng->reseed_done);
		spin_lock_irq(&trng->write_lock);
		writel(cmd, trng->base + STARFIVE_CTRL);
		spin_unlock_irq(&trng->write_lock);
		if (!wait_for_completion_timeout(&trng->reseed_done, usecs_to_jiffies(wait_time)))
			return -ETIMEDOUT;
		break;
	default:
		return -EINVAL;
	}

	return 0;
}

static int starfive_trng_init(struct hwrng *rng)
{
	struct starfive_trng *trng = to_trng(rng);
	u32 mode, intr = 0;

	/* setup Auto Request/Age register */
	writel(autoage, trng->base + STARFIVE_AUTO_AGE);
	writel(autoreq, trng->base + STARFIVE_AUTO_RQSTS);

	/* clear register: ISTAT */
	starfive_trng_irq_mask_clear(trng);

	intr |= STARFIVE_IE_ALL;
	writel(intr, trng->base + STARFIVE_IE);

	mode  = readl(trng->base + STARFIVE_MODE);

	switch (trng->mode) {
	case PRNG_128BIT:
		mode &= ~STARFIVE_MODE_R256;
		break;
	case PRNG_256BIT:
		mode |= STARFIVE_MODE_R256;
		break;
	default:
		mode |= STARFIVE_MODE_R256;
		break;
	}

	writel(mode, trng->base + STARFIVE_MODE);

	return starfive_trng_cmd(trng, STARFIVE_CTRL_EXEC_RANDRESEED, 1);
}

static irqreturn_t starfive_trng_irq(int irq, void *priv)
{
	u32 status;
	struct starfive_trng *trng = (struct starfive_trng *)priv;

	status = readl(trng->base + STARFIVE_ISTAT);
	if (status & STARFIVE_ISTAT_RAND_RDY) {
		writel(STARFIVE_ISTAT_RAND_RDY, trng->base + STARFIVE_ISTAT);
		complete(&trng->random_done);
	}

	if (status & STARFIVE_ISTAT_SEED_DONE) {
		writel(STARFIVE_ISTAT_SEED_DONE, trng->base + STARFIVE_ISTAT);
		complete(&trng->reseed_done);
	}

	if (status & STARFIVE_ISTAT_LFSR_LOCKUP) {
		writel(STARFIVE_ISTAT_LFSR_LOCKUP, trng->base + STARFIVE_ISTAT);
		/* SEU occurred, reseeding required*/
		spin_lock(&trng->write_lock);
		writel(STARFIVE_CTRL_EXEC_RANDRESEED, trng->base + STARFIVE_CTRL);
		spin_unlock(&trng->write_lock);
	}

	return IRQ_HANDLED;
}

static void starfive_trng_cleanup(struct hwrng *rng)
{
	struct starfive_trng *trng = to_trng(rng);

	writel(0, trng->base + STARFIVE_CTRL);

	reset_control_assert(trng->rst);
	clk_disable_unprepare(trng->hclk);
	clk_disable_unprepare(trng->ahb);
}

static int starfive_trng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
{
	struct starfive_trng *trng = to_trng(rng);
	int ret;

	pm_runtime_get_sync(trng->dev);

	if (trng->mode == PRNG_256BIT)
		max = min_t(size_t, max, (STARFIVE_RAND_LEN * 8));
	else
		max = min_t(size_t, max, (STARFIVE_RAND_LEN * 4));

	if (wait) {
		ret = starfive_trng_wait_idle(trng);
		if (ret)
			return -ETIMEDOUT;
	}

	ret = starfive_trng_cmd(trng, STARFIVE_CTRL_GENE_RANDNUM, wait);
	if (ret)
		return ret;

	memcpy_fromio(buf, trng->base + STARFIVE_RAND0, max);

	pm_runtime_put_sync_autosuspend(trng->dev);

	return max;
}

static int starfive_trng_probe(struct platform_device *pdev)
{
	int ret;
	int irq;
	struct starfive_trng *trng;

	trng = devm_kzalloc(&pdev->dev, sizeof(*trng), GFP_KERNEL);
	if (!trng)
		return -ENOMEM;

	platform_set_drvdata(pdev, trng);
	trng->dev = &pdev->dev;

	trng->base = devm_platform_ioremap_resource(pdev, 0);
	if (IS_ERR(trng->base))
		return dev_err_probe(&pdev->dev, PTR_ERR(trng->base),
				     "Error remapping memory for platform device.\n");

	irq = platform_get_irq(pdev, 0);
	if (irq < 0)
		return irq;

	init_completion(&trng->random_done);
	init_completion(&trng->reseed_done);
	spin_lock_init(&trng->write_lock);

	ret = devm_request_irq(&pdev->dev, irq, starfive_trng_irq, 0, pdev->name,
			       (void *)trng);
	if (ret)
		return dev_err_probe(&pdev->dev, irq,
				     "Failed to register interrupt handler\n");

	trng->hclk = devm_clk_get(&pdev->dev, "hclk");
	if (IS_ERR(trng->hclk))
		return dev_err_probe(&pdev->dev, PTR_ERR(trng->hclk),
				     "Error getting hardware reference clock\n");

	trng->ahb = devm_clk_get(&pdev->dev, "ahb");
	if (IS_ERR(trng->ahb))
		return dev_err_probe(&pdev->dev, PTR_ERR(trng->ahb),
				     "Error getting ahb reference clock\n");

	trng->rst = devm_reset_control_get_shared(&pdev->dev, NULL);
	if (IS_ERR(trng->rst))
		return dev_err_probe(&pdev->dev, PTR_ERR(trng->rst),
				     "Error getting hardware reset line\n");

	clk_prepare_enable(trng->hclk);
	clk_prepare_enable(trng->ahb);
	reset_control_deassert(trng->rst);

	trng->rng.name = dev_driver_string(&pdev->dev);
	trng->rng.init = starfive_trng_init;
	trng->rng.cleanup = starfive_trng_cleanup;
	trng->rng.read = starfive_trng_read;

	trng->mode = PRNG_256BIT;
	trng->mission = 1;
	trng->reseed = RANDOM_RESEED;

	pm_runtime_use_autosuspend(&pdev->dev);
	pm_runtime_set_autosuspend_delay(&pdev->dev, 100);
	pm_runtime_enable(&pdev->dev);

	ret = devm_hwrng_register(&pdev->dev, &trng->rng);
	if (ret) {
		pm_runtime_disable(&pdev->dev);

		reset_control_assert(trng->rst);
		clk_disable_unprepare(trng->ahb);
		clk_disable_unprepare(trng->hclk);

		return dev_err_probe(&pdev->dev, ret, "Failed to register hwrng\n");
	}

	return 0;
}

static int __maybe_unused starfive_trng_suspend(struct device *dev)
{
	struct starfive_trng *trng = dev_get_drvdata(dev);

	clk_disable_unprepare(trng->hclk);
	clk_disable_unprepare(trng->ahb);

	return 0;
}

static int __maybe_unused starfive_trng_resume(struct device *dev)
{
	struct starfive_trng *trng = dev_get_drvdata(dev);

	clk_prepare_enable(trng->hclk);
	clk_prepare_enable(trng->ahb);

	return 0;
}

static DEFINE_SIMPLE_DEV_PM_OPS(starfive_trng_pm_ops, starfive_trng_suspend,
				starfive_trng_resume);

static const struct of_device_id trng_dt_ids[] __maybe_unused = {
	{ .compatible = "starfive,jh7110-trng" },
	{ }
};
MODULE_DEVICE_TABLE(of, trng_dt_ids);

static struct platform_driver starfive_trng_driver = {
	.probe	= starfive_trng_probe,
	.driver	= {
		.name		= "jh7110-trng",
		.pm		= &starfive_trng_pm_ops,
		.of_match_table	= of_match_ptr(trng_dt_ids),
	},
};

module_platform_driver(starfive_trng_driver);

MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("StarFive True Random Number Generator");