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/* SPDX-License-Identifier: GPL-2.0-only */
/* Inspired by OvmfPkg/QemuFlashFvbServicesRuntimeDxe/QemuFlash.c from edk2 */
#include <arch/mmio.h>
#include <boot_device.h>
#include <console/console.h>
#include <commonlib/helpers.h>
#include <commonlib/region.h>
#include <string.h>
#define WRITE_BYTE_CMD 0x10
#define BLOCK_ERASE_CMD 0x20
#define CLEAR_STATUS_CMD 0x50
#define READ_STATUS_CMD 0x70
#define BLOCK_ERASE_CONFIRM_CMD 0xD0
#define READ_ARRAY_CMD 0xFF
#define CLEARED_ARRAY_STATUS 0x00
#define QEMU_FLASH_BLOCK_SIZE 0x1000
#if CONFIG(ELOG)
#include <southbridge/intel/common/pmutil.h>
/*
* ELOG and VBOOT options are automatically enabled when building with
* CHROMEOS=y. While the former allows for logging PCH state (not that there is
* much to log on QEMU), the latter currently forces 16 MiB ROM size, which in
* turn doesn't allow mounting as pflash in QEMU. Using pflash is required to
* have writable flash, which means that the following function will not be
* able to write to the flash based log until ROM size and layout is changed in
* Flashmap used when building for vboot.
*/
void pch_log_state(void) {}
#endif
static ssize_t qemu_writeat(const struct region_device *rd, const void *b,
size_t offset, size_t size)
{
const struct mem_region_device *mdev;
size_t i;
volatile char *ptr;
const char *buf = b;
mdev = container_of(rd, __typeof__(*mdev), rdev);
ptr = &mdev->base[offset];
for (i = 0; i < size; i++) {
write8(ptr, WRITE_BYTE_CMD);
write8(ptr, buf[i]);
ptr++;
}
/* Restore flash to read mode. */
if (size > 0) {
write8(ptr - 1, READ_ARRAY_CMD);
}
return size;
}
static ssize_t qemu_eraseat(const struct region_device *rd, size_t offset,
size_t size)
{
const struct mem_region_device *mdev;
size_t i;
volatile char *ptr;
mdev = container_of(rd, __typeof__(*mdev), rdev);
ptr = &mdev->base[offset];
if (!IS_ALIGNED(offset, QEMU_FLASH_BLOCK_SIZE)) {
printk(BIOS_ERR, "%s: erased offset isn't multiple of block size\n",
__func__);
return -1;
}
if (!IS_ALIGNED(size, QEMU_FLASH_BLOCK_SIZE)) {
printk(BIOS_ERR, "%s: erased size isn't multiple of block size\n",
__func__);
return -1;
}
for (i = 0; i < size; i += QEMU_FLASH_BLOCK_SIZE) {
write8(ptr, BLOCK_ERASE_CMD);
write8(ptr, BLOCK_ERASE_CONFIRM_CMD);
ptr += QEMU_FLASH_BLOCK_SIZE;
}
/* Restore flash to read mode. */
if (size > 0) {
write8(ptr - QEMU_FLASH_BLOCK_SIZE, READ_ARRAY_CMD);
}
return size;
}
static struct region_device_ops flash_ops;
static const struct mem_region_device boot_dev =
MEM_REGION_DEV_INIT(0x100000000ULL - CONFIG_ROM_SIZE, CONFIG_ROM_SIZE, &flash_ops);
/*
* Depending on how firmware image was passed to QEMU, it may behave as:
*
* - ROM - memory mapped reads, writes are ignored (FW image mounted with
* '-bios');
* - RAM - memory mapped reads and writes (FW image mounted with e.g.
* '-device loader');
* - flash - memory mapped reads, write and erase possible through commands.
* Contrary to physical flash devices erase is not required before writing,
* but it also doesn't hurt. Flash may be split into read-only and read-write
* parts, like OVMF_CODE.fd and OVMF_VARS.fd. Maximal combined size of system
* firmware is hardcoded (QEMU < 5.0.0) or set by default to 8 MiB. On QEMU
* version 5.0.0 or newer, it is configurable with `max-fw-size` machine
* configuration option, up to 16 MiB to not overlap with IOAPIC memory range
* (FW image(s) mounted with '-drive if=pflash').
*
* This function detects which of the above applies and fills region_device_ops
* accordingly.
*/
void boot_device_init(void)
{
volatile char *ptr;
char original, readback;
static bool initialized = false;
if (initialized)
return;
/*
* mmap, munmap and readat are always identical to mem_rdev_rw_ops, other
* functions may vary.
*/
flash_ops = mem_rdev_rw_ops;
/*
* Find first byte different than any of the commands, simplified.
*
* Detection code few lines below writes commands and tries to read back
* the response. To make that code simpler, make sure that original byte
* is different than any of the commands or expected responses. It is
* expected that such byte will always be found - it is virtually
* impossible to write valid x86 code with just bytes ending with 0, and
* there are also ASCII characters in metadata (CBFS, FMAP) that has bytes
* matching those assumptions.
*/
ptr = (volatile char *)boot_dev.base;
original = read8(ptr);
while (original == (char)0xFF || (original & 0x0F) == 0)
original = read8(++ptr);
/*
* Detect what type of flash we're dealing with. This also clears any stale
* status bits, so the next read of status register should return known
* value (if pflash is used).
*/
write8(ptr, CLEAR_STATUS_CMD);
readback = read8(ptr);
if (readback == CLEAR_STATUS_CMD) {
printk(BIOS_DEBUG, "QEMU flash behaves as RAM\n");
/* Restore original content. */
write8(ptr, original);
} else {
/* Either ROM or QEMU flash implementation. */
write8(ptr, READ_STATUS_CMD);
readback = read8(ptr);
if (readback == original) {
printk(BIOS_DEBUG, "QEMU flash behaves as ROM\n");
/* ROM means no writing nor erasing. */
flash_ops.writeat = NULL;
flash_ops.eraseat = NULL;
} else if (readback == CLEARED_ARRAY_STATUS) {
/* Try writing original value to test whether flash is writable. */
write8(ptr, WRITE_BYTE_CMD);
write8(ptr, original);
write8(ptr, READ_STATUS_CMD);
readback = read8(ptr);
if (readback & 0x10 /* programming error */) {
printk(BIOS_DEBUG,
"QEMU flash behaves as write-protected flash\n");
flash_ops.writeat = NULL;
flash_ops.eraseat = NULL;
} else {
printk(BIOS_DEBUG, "QEMU flash behaves as writable flash\n");
flash_ops.writeat = qemu_writeat;
flash_ops.eraseat = qemu_eraseat;
}
/* Restore flash to read mode. */
write8(ptr, READ_ARRAY_CMD);
} else {
printk(BIOS_ERR, "Unexpected QEMU flash behavior, assuming ROM\n");
/*
* This shouldn't happen and first byte of flash may already be
* corrupted by testing, but don't take any further risk.
*/
flash_ops.writeat = NULL;
flash_ops.eraseat = NULL;
}
}
initialized = true;
}
/* boot_device_ro() is defined in arch/x86/mmap_boot.c */
const struct region_device *boot_device_rw(void)
{
return &boot_dev.rdev;
}
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