/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

/* Flash memory module for Chrome EC */

#include "flash.h"
#include "registers.h"
#include "switch.h"
#include "system.h"
#include "timer.h"
#include "util.h"
#include "watchdog.h"

#define FLASH_FWB_WORDS 32
#define FLASH_FWB_BYTES (FLASH_FWB_WORDS * 4)

#define BANK_SHIFT 5 /* bank registers have 32bits each, 2^32 */
#define BANK_MASK ((1 << BANK_SHIFT) - 1) /* 5 bits */
#define F_BANK(b) ((b) >> BANK_SHIFT)
#define F_BIT(b) (1 << ((b) & BANK_MASK))

/* Flash timeouts.  These are 2x the spec sheet max. */
#define ERASE_TIMEOUT_MS 200
#define WRITE_TIMEOUT_US 300

int stuck_locked;  /* Is physical flash stuck protected? */
int all_protected; /* Has all-flash protection been requested? */

/**
 * Protect flash banks until reboot.
 *
 * @param start_bank    Start bank to protect
 * @param bank_count    Number of banks to protect
 */
static void protect_banks(int start_bank, int bank_count)
{
	int bank;
	for (bank = start_bank; bank < start_bank + bank_count; bank++)
		LM4_FLASH_FMPPE[F_BANK(bank)] &= ~F_BIT(bank);
}

/**
 * Perform a write-buffer operation.  Buffer (FWB) and address (FMA) must be
 * pre-loaded.
 *
 * @return EC_SUCCESS, or nonzero if error.
 */
static int write_buffer(void)
{
	int t;

	if (all_protected)
		return EC_ERROR_ACCESS_DENIED;

	if (!LM4_FLASH_FWBVAL)
		return EC_SUCCESS;  /* Nothing to do */

	/* Clear previous error status */
	LM4_FLASH_FCMISC = LM4_FLASH_FCRIS;

	/* Start write operation at page boundary */
	LM4_FLASH_FMC2 = 0xa4420001;

	/*
	 * Reload the watchdog timer, so that writing a large amount of flash
	 * doesn't cause a watchdog reset.
	 */
	watchdog_reload();

	/* Wait for write to complete */
	for (t = 0; LM4_FLASH_FMC2 & 0x01; t += 10) {
		if (t > WRITE_TIMEOUT_US)
			return EC_ERROR_TIMEOUT;
		udelay(10);
	}

	/* Check for error conditions - program failed, erase needed,
	 * voltage error. */
	if (LM4_FLASH_FCRIS & 0x2e01)
		return EC_ERROR_UNKNOWN;

	return EC_SUCCESS;
}

/*****************************************************************************/
/* Physical layer APIs */

int flash_physical_write(int offset, int size, const char *data)
{
	const uint32_t *data32 = (const uint32_t *)data;
	int rv;
	int i;

	if (all_protected)
		return EC_ERROR_ACCESS_DENIED;

	/* Fail if offset, size, and data aren't at least word-aligned */
	if ((offset | size | (uint32_t)(uintptr_t)data) & 3)
		return EC_ERROR_INVAL;

	/* Get initial write buffer index and page */
	LM4_FLASH_FMA = offset & ~(FLASH_FWB_BYTES - 1);
	i = (offset >> 2) & (FLASH_FWB_WORDS - 1);

	/* Copy words into buffer */
	for (; size > 0; size -= 4) {
		LM4_FLASH_FWB[i++] = *data32++;
		if (i == FLASH_FWB_WORDS) {
			rv = write_buffer();
			if (rv != EC_SUCCESS)
				return rv;

			/* Advance to next page */
			i = 0;
			LM4_FLASH_FMA += FLASH_FWB_BYTES;
		}
	}

	/* Handle final partial page, if any */
	if (i > 0)
		return write_buffer();

	return EC_SUCCESS;
}

int flash_physical_erase(int offset, int size)
{
	if (all_protected)
		return EC_ERROR_ACCESS_DENIED;

	LM4_FLASH_FCMISC = LM4_FLASH_FCRIS;  /* Clear previous error status */

	for (; size > 0; size -= CONFIG_FLASH_ERASE_SIZE,
		     offset += CONFIG_FLASH_ERASE_SIZE) {
		int t;

		/* Do nothing if already erased */
		if (flash_is_erased(offset, CONFIG_FLASH_ERASE_SIZE))
			continue;

		LM4_FLASH_FMA = offset;

		/*
		 * Reload the watchdog timer, so that erasing many flash pages
		 * doesn't cause a watchdog reset.  May not need this now that
		 * we're using msleep() below.
		 */
		watchdog_reload();

		/* Start erase */
		LM4_FLASH_FMC = 0xa4420002;

		/* Wait for erase to complete */
		for (t = 0; LM4_FLASH_FMC & 0x02; t++) {
			if (t > ERASE_TIMEOUT_MS)
				return EC_ERROR_TIMEOUT;
			msleep(1);
		}

		/* Check for error conditions - erase failed, voltage error,
		 * protection error */
		if (LM4_FLASH_FCRIS & 0x0a01)
			return EC_ERROR_UNKNOWN;
	}

	return EC_SUCCESS;
}

int flash_physical_get_protect(int bank)
{
	return (LM4_FLASH_FMPPE[F_BANK(bank)] & F_BIT(bank)) ? 0 : 1;
}

uint32_t flash_physical_get_protect_flags(void)
{
	uint32_t flags = 0;

	/* Read all-protected state from our shadow copy */
	if (all_protected)
		flags |= EC_FLASH_PROTECT_ALL_NOW;

	/* Check if blocks were stuck locked at pre-init */
	if (stuck_locked)
		flags |= EC_FLASH_PROTECT_ERROR_STUCK;

	return flags;
}

int flash_physical_protect_now(int all)
{
	if (all) {
		/* Protect the entire flash */
		all_protected = 1;
		protect_banks(0, CONFIG_FLASH_SIZE /
			      CONFIG_FLASH_BANK_SIZE);
	} else
		/* Protect the WP region (read-only section and pstate) */
		protect_banks(WP_BANK_OFFSET, WP_BANK_COUNT);

	return EC_SUCCESS;
}

uint32_t flash_physical_get_valid_flags(void)
{
	return EC_FLASH_PROTECT_RO_AT_BOOT |
	       EC_FLASH_PROTECT_RO_NOW |
	       EC_FLASH_PROTECT_ALL_NOW;
}

uint32_t flash_physical_get_writable_flags(uint32_t cur_flags)
{
	uint32_t ret = 0;

	/* If RO protection isn't enabled, its at-boot state can be changed. */
	if (!(cur_flags & EC_FLASH_PROTECT_RO_NOW))
		ret |= EC_FLASH_PROTECT_RO_AT_BOOT;

	/*
	 * If entire flash isn't protected at this boot, it can be enabled if
	 * the WP GPIO is asserted.
	 */
	if (!(cur_flags & EC_FLASH_PROTECT_ALL_NOW) &&
	    (cur_flags & EC_FLASH_PROTECT_GPIO_ASSERTED))
		ret |= EC_FLASH_PROTECT_ALL_NOW;

	return ret;
}


/*****************************************************************************/
/* High-level APIs */

int flash_pre_init(void)
{
	uint32_t reset_flags = system_get_reset_flags();
	uint32_t prot_flags = flash_get_protect();
	uint32_t unwanted_prot_flags = EC_FLASH_PROTECT_ALL_NOW |
		EC_FLASH_PROTECT_ERROR_INCONSISTENT;

	/*
	 * If we have already jumped between images, an earlier image could
	 * have applied write protection.  Nothing additional needs to be done.
	 */
	if (reset_flags & RESET_FLAG_SYSJUMP)
		return EC_SUCCESS;

	if (prot_flags & EC_FLASH_PROTECT_GPIO_ASSERTED) {
		/*
		 * Write protect is asserted.  If we want RO flash protected,
		 * protect it now.
		 */
		if ((prot_flags & EC_FLASH_PROTECT_RO_AT_BOOT) &&
		    !(prot_flags & EC_FLASH_PROTECT_RO_NOW)) {
			int rv = flash_set_protect(EC_FLASH_PROTECT_RO_NOW,
						   EC_FLASH_PROTECT_RO_NOW);
			if (rv)
				return rv;

			/* Re-read flags */
			prot_flags = flash_get_protect();
		}

		/* Update all-now flag if all flash is protected */
		if (prot_flags & EC_FLASH_PROTECT_ALL_NOW)
			all_protected = 1;

	} else {
		/* Don't want RO flash protected */
		unwanted_prot_flags |= EC_FLASH_PROTECT_RO_NOW;
	}

	/* If there are no unwanted flags, done */
	if (!(prot_flags & unwanted_prot_flags))
		return EC_SUCCESS;

	/*
	 * If the last reboot was a power-on reset, it should have cleared
	 * write-protect.  If it didn't, then the flash write protect registers
	 * have been permanently committed and we can't fix that.
	 */
	if (reset_flags & RESET_FLAG_POWER_ON) {
		stuck_locked = 1;
		return EC_ERROR_ACCESS_DENIED;
	}

	/* Otherwise, do a hard boot to clear the flash protection registers */
	system_reset(SYSTEM_RESET_HARD | SYSTEM_RESET_PRESERVE_FLAGS);

	/* That doesn't return, so if we're still here that's an error */
	return EC_ERROR_UNKNOWN;
}
