// SPDX-License-Identifier: BSD-2-Clause
/*
 * Copyright (c) 2016, Linaro Limited
 */

#include <initcall.h>
#include <io.h>
#include <keep.h>
#include <kernel/interrupt.h>
#include <kernel/misc.h>
#include <kernel/spinlock.h>
#include <mm/core_memprot.h>
#include <mm/core_mmu.h>
#include <platform_config.h>
#include <rng_support.h>

#define	RNG_OUTPUT_L            0x0000
#define	RNG_OUTPUT_H            0x0004
#define	RNG_STATUS              0x0008
#  define RNG_READY             BIT(0)
#  define SHUTDOWN_OFLO         BIT(1)
#define	RNG_INTMASK             0x000C
#define	RNG_INTACK              0x0010
#define	RNG_CONTROL             0x0014
#  define ENABLE_TRNG           BIT(10)
#define	RNG_CONFIG              0x0018
#define	RNG_ALARMCNT            0x001C
#define	RNG_FROENABLE           0x0020
#define	RNG_FRODETUNE           0x0024
#define	RNG_ALARMMASK           0x0028
#define	RNG_ALARMSTOP           0x002C
#define	RNG_LFSR_L              0x0030
#define	RNG_LFSR_M              0x0034
#define	RNG_LFSR_H              0x0038
#define	RNG_COUNT               0x003C
#define	RNG_OPTIONS             0x0078
#define	RNG_EIP_REV             0x007C
#define	RNG_MMR_STATUS_EN       0x1FD8
#define	RNG_REV                 0x1FE0
#define	RNG_SYS_CONFIG_REG      0x1FE4
#  define RNG_AUTOIDLE          BIT(0)
#define	RNG_MMR_STATUS_SET      0x1FEC
#define	RNG_SOFT_RESET_REG      0x1FF0
#  define RNG_SOFT_RESET        BIT(0)
#define	RNG_IRQ_EOI_REG         0x1FF4
#define	RNG_IRQSTATUS           0x1FF8

#define RNG_CONTROL_STARTUP_CYCLES_SHIFT        16
#define RNG_CONTROL_STARTUP_CYCLES_MASK         GENMASK_32(31, 16)

#define RNG_CONFIG_MAX_REFIL_CYCLES_SHIFT       16
#define RNG_CONFIG_MAX_REFIL_CYCLES_MASK        GENMASK_32(31, 16)
#define RNG_CONFIG_MIN_REFIL_CYCLES_SHIFT       0
#define RNG_CONFIG_MIN_REFIL_CYCLES_MASK        GENMASK_32(7, 0)

#define RNG_ALARMCNT_ALARM_TH_SHIFT             0
#define RNG_ALARMCNT_ALARM_TH_MASK              GENMASK_32(7, 0)
#define RNG_ALARMCNT_SHUTDOWN_TH_SHIFT          16
#define RNG_ALARMCNT_SHUTDOWN_TH_MASK           GENMASK_32(20, 16)

#define RNG_CONTROL_STARTUP_CYCLES              0xff
#define RNG_CONFIG_MIN_REFIL_CYCLES             0x21
#define RNG_CONFIG_MAX_REFIL_CYCLES             0x22
#define RNG_ALARM_THRESHOLD                     0xff
#define RNG_SHUTDOWN_THRESHOLD                  0x4

#define RNG_FRO_MASK    GENMASK_32(23, 0)

#define RNG_REG_SIZE    0x2000

register_phys_mem_pgdir(MEM_AREA_IO_SEC, RNG_BASE, RNG_REG_SIZE);

static unsigned int rng_lock = SPINLOCK_UNLOCK;
static vaddr_t rng;

static void dra7_rng_read64(uint32_t *low_word, uint32_t *high_word)
{
	/* Is the result ready (available)? */
	while (!(io_read32(rng + RNG_STATUS) & RNG_READY)) {
		/* Is the shutdown threshold reached? */
		if (io_read32(rng + RNG_STATUS) & SHUTDOWN_OFLO) {
			uint32_t alarm = io_read32(rng + RNG_ALARMSTOP);
			uint32_t tune = io_read32(rng + RNG_FRODETUNE);

			/* Clear the alarm events */
			io_write32(rng + RNG_ALARMMASK, 0x0);
			io_write32(rng + RNG_ALARMSTOP, 0x0);
			/* De-tune offending FROs */
			io_write32(rng + RNG_FRODETUNE, tune ^ alarm);
			/* Re-enable the shut down FROs */
			io_write32(rng + RNG_FROENABLE, RNG_FRO_MASK);
			/* Clear the shutdown overflow event */
			io_write32(rng + RNG_INTACK, SHUTDOWN_OFLO);

			DMSG("Fixed FRO shutdown\n");
		}
	}
	/* Read random value */
	*low_word = io_read32(rng + RNG_OUTPUT_L);
	*high_word = io_read32(rng + RNG_OUTPUT_H);
	/* Acknowledge read complete */
	io_write32(rng + RNG_INTACK, RNG_READY);
}

TEE_Result hw_get_random_bytes(void *buf, size_t len)
{
	static union {
		uint32_t val[2];
		uint8_t byte[8];
	} fifo;
	static size_t fifo_pos;
	uint8_t *buffer = buf;
	size_t buffer_pos = 0;

	while (buffer_pos < len) {
		uint32_t exceptions = cpu_spin_lock_xsave(&rng_lock);

		/* Refill our FIFO */
		if (fifo_pos == 0)
			dra7_rng_read64(&fifo.val[0], &fifo.val[1]);

		buffer[buffer_pos++] = fifo.byte[fifo_pos++];
		fifo_pos %= 8;

		cpu_spin_unlock_xrestore(&rng_lock, exceptions);
	}

	return TEE_SUCCESS;
}

static TEE_Result dra7_rng_init(void)
{
	uint32_t val;

	rng = (vaddr_t)phys_to_virt(RNG_BASE, MEM_AREA_IO_SEC, RNG_REG_SIZE);

	/* Execute a software reset */
	io_write32(rng + RNG_SOFT_RESET_REG, RNG_SOFT_RESET);

	/* Wait for the software reset completion by polling */
	while (io_read32(rng + RNG_SOFT_RESET_REG) & RNG_SOFT_RESET)
		;

	/* Switch to low-power operating mode */
	io_write32(rng + RNG_SYS_CONFIG_REG, RNG_AUTOIDLE);

	/*
	 * Select the number of clock input cycles to the
	 * FROs between two samples
	 */
	val = 0;

	/* Ensure initial latency */
	val |= RNG_CONFIG_MIN_REFIL_CYCLES <<
			RNG_CONFIG_MIN_REFIL_CYCLES_SHIFT;
	val |= RNG_CONFIG_MAX_REFIL_CYCLES <<
			RNG_CONFIG_MAX_REFIL_CYCLES_SHIFT;
	io_write32(rng + RNG_CONFIG, val);

	/* Configure the desired FROs */
	io_write32(rng + RNG_FRODETUNE, 0x0);

	/* Enable all FROs */
	io_write32(rng + RNG_FROENABLE, 0xffffff);

	/*
	 * Select the maximum number of samples after
	 * which if a repeating pattern is still detected, an
	 * alarm event is generated
	 */
	val = RNG_ALARM_THRESHOLD << RNG_ALARMCNT_ALARM_TH_SHIFT;

	/*
	 * Set the shutdown threshold to the number of FROs
	 * allowed to be shut downed
	 */
	val |= RNG_SHUTDOWN_THRESHOLD << RNG_ALARMCNT_SHUTDOWN_TH_SHIFT;
	io_write32(rng + RNG_ALARMCNT, val);

	/* Enable the RNG module */
	val = RNG_CONTROL_STARTUP_CYCLES << RNG_CONTROL_STARTUP_CYCLES_SHIFT;
	val |= ENABLE_TRNG;
	io_write32(rng + RNG_CONTROL, val);

	IMSG("DRA7x TRNG initialized");

	return TEE_SUCCESS;
}
driver_init(dra7_rng_init);
