spi-nor: Add support for Intel SPI serial flash controller

Upgrading BIOS using intel-spi

------------------------------

Many Intel CPUs like Baytrail and Braswell include SPI serial flash host

controller which is used to hold BIOS and other platform specific data.

Since contents of the SPI serial flash is crucial for machine to function,

it is typically protected by different hardware protection mechanisms to

avoid accidental (or on purpose) overwrite of the content.

Not all manufacturers protect the SPI serial flash, mainly because it

allows upgrading the BIOS image directly from an OS.

The intel-spi driver makes it possible to read and write the SPI serial

flash, if certain protection bits are not set and locked. If it finds

any of them set, the whole MTD device is made read-only to prevent

partial overwrites. By default the driver exposes SPI serial flash

contents as read-only but it can be changed from kernel command line,

passing "intel-spi.writeable=1".

Please keep in mind that overwriting the BIOS image on SPI serial flash

might render the machine unbootable and requires special equipment like

Dediprog to revive. You have been warned!

Below are the steps how to upgrade MinnowBoard MAX BIOS directly from

Linux.

 1) Download and extract the latest Minnowboard MAX BIOS SPI image

    [1]. At the time writing this the latest image is v92.

 2) Install mtd-utils package [2]. We need this in order to erase the SPI

    serial flash. Distros like Debian and Fedora have this prepackaged with

    name "mtd-utils".

 3) Add "intel-spi.writeable=1" to the kernel command line and reboot

    the board (you can also reload the driver passing "writeable=1" as

    module parameter to modprobe).

 4) Once the board is up and running again, find the right MTD partition

    (it is named as "BIOS"):

    # cat /proc/mtd

    dev:    size   erasesize  name

    mtd0: 00800000 00001000 "BIOS"

    So here it will be /dev/mtd0 but it may vary.

 5) Make backup of the existing image first:

    # dd if=/dev/mtd0ro of=bios.bak

    16384+0 records in

    16384+0 records out

    8388608 bytes (8.4 MB) copied, 10.0269 s, 837 kB/s

 6) Verify the backup

    # sha1sum /dev/mtd0ro bios.bak

    fdbb011920572ca6c991377c4b418a0502668b73  /dev/mtd0ro

    fdbb011920572ca6c991377c4b418a0502668b73  bios.bak

    The SHA1 sums must match. Otherwise do not continue any further!

 7) Erase the SPI serial flash. After this step, do not reboot the

    board! Otherwise it will not start anymore.

    # flash_erase /dev/mtd0 0 0

    Erasing 4 Kibyte @ 7ff000 -- 100 % complete

 8) Once completed without errors you can write the new BIOS image:

    # dd if=MNW2MAX1.X64.0092.R01.1605221712.bin of=/dev/mtd0

 9) Verify that the new content of the SPI serial flash matches the new

    BIOS image:

    # sha1sum /dev/mtd0ro MNW2MAX1.X64.0092.R01.1605221712.bin

    9b4df9e4be2057fceec3a5529ec3d950836c87a2  /dev/mtd0ro

    9b4df9e4be2057fceec3a5529ec3d950836c87a2 MNW2MAX1.X64.0092.R01.1605221712.bin

    The SHA1 sums should match.

 10) Now you can reboot your board and observe the new BIOS starting up

     properly.

References

----------

[1] https://firmware.intel.com/sites/default/files/MinnowBoard.MAX_.X64.92.R01.zip

[2] http://www.linux-mtd.infradead.org/

	  Flash. Enable this option if you have a device with a SPIFI

	  controller and want to access the Flash as a mtd device.

config SPI_INTEL_SPI

	tristate

config SPI_INTEL_SPI_PLATFORM

	tristate "Intel PCH/PCU SPI flash platform driver" if EXPERT

	depends on X86

	select SPI_INTEL_SPI

	help

	  This enables platform support for the Intel PCH/PCU SPI

	  controller in master mode. This controller is present in modern

	  Intel hardware and is used to hold BIOS and other persistent

	  settings. Using this driver it is possible to upgrade BIOS

	  directly from Linux.

	  Say N here unless you know what you are doing. Overwriting the

	  SPI flash may render the system unbootable.

	  To compile this driver as a module, choose M here: the module

	  will be called intel-spi-platform.

endif # MTD_SPI_NOR

obj-$(CONFIG_SPI_HISI_SFC)	+= hisi-sfc.o

obj-$(CONFIG_MTD_MT81xx_NOR)    += mtk-quadspi.o

obj-$(CONFIG_SPI_NXP_SPIFI)	+= nxp-spifi.o

obj-$(CONFIG_SPI_INTEL_SPI)	+= intel-spi.o

obj-$(CONFIG_SPI_INTEL_SPI_PLATFORM)	+= intel-spi-platform.o

/*

 * Intel PCH/PCU SPI flash platform driver.

 *

 * Copyright (C) 2016, Intel Corporation

 * Author: Mika Westerberg <mika.westerberg@linux.intel.com>

 *

 * This program is free software; you can redistribute it and/or modify

 * it under the terms of the GNU General Public License version 2 as

 * published by the Free Software Foundation.

 */

#include <linux/ioport.h>

#include <linux/module.h>

#include <linux/platform_device.h>

#include "intel-spi.h"

static int intel_spi_platform_probe(struct platform_device *pdev)

{

	struct intel_spi_boardinfo *info;

	struct intel_spi *ispi;

	struct resource *mem;

	info = dev_get_platdata(&pdev->dev);

	if (!info)

		return -EINVAL;

	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);

	ispi = intel_spi_probe(&pdev->dev, mem, info);

	if (IS_ERR(ispi))

		return PTR_ERR(ispi);

	platform_set_drvdata(pdev, ispi);

	return 0;

}

static int intel_spi_platform_remove(struct platform_device *pdev)

{

	struct intel_spi *ispi = platform_get_drvdata(pdev);

	return intel_spi_remove(ispi);

}

static struct platform_driver intel_spi_platform_driver = {

	.probe = intel_spi_platform_probe,

	.remove = intel_spi_platform_remove,

	.driver = {

		.name = "intel-spi",

	},

};

module_platform_driver(intel_spi_platform_driver);

MODULE_DESCRIPTION("Intel PCH/PCU SPI flash platform driver");

MODULE_AUTHOR("Mika Westerberg <mika.westerberg@linux.intel.com>");

MODULE_LICENSE("GPL v2");

MODULE_ALIAS("platform:intel-spi");