flashrom

The first thing that came to my mind is something like that:

static int atahpt_toggle_flash_access(struct atahpt_data *data, int toggle)
{
	uint32_t reg32 = 0;

	if (toggle) {
		data->flash_access = pci_read_long(data->dev, REG_FLASH_ACCESS);
		reg32 = BIT(BIT_FLASH_ACCESS);
	}

	reg32 |= data->flash_access;

	pci_write_long(data->dev, REG_FLASH_ACCESS, reg32);
	return 0;
}