Documentation: Add basic flashing tutorial for Lenovo

* Add basic flashing tutorial
** Describe internal and external flashing
** Describe flash supply diode protection
** Gives general advices on flashing
** Describe how to use flashrom --ifd
*  Describe basic flashing on Lenovo T4xx devices
** Describe how to disassemble and access the flash IC on T4xx
** Describe flash layout on Sandy Bridge and Ivy Bridge series.

Change-Id: Ia833e27f4e7d89ee32be9bed21a0c021839facec
Signed-off-by: Patrick Rudolph <siro@das-labor.org>
Reviewed-on: https://review.coreboot.org/27852
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Philipp Deppenwiese <zaolin.daisuki@gmail.com>

7 files changed, 313 insertions, 0 deletions

diff --git a/Documentation/flash_tutorial/ext_power.md b/Documentation/flash_tutorial/ext_power.md
new file mode 100644
index 000000000000..542ccfd934f0
--- /dev/null
+++ b/Documentation/flash_tutorial/ext_power.md
@@ -0,0 +1,28 @@
+# Flashing firmware externally supplying direct power
+
+**WARNING:** Never use a high current rated power supply, like PC ATX power
+             supply. It'll literally melt your PCB traces on short circuit.
+
+On some mainboards the flash IC Vcc pin is connected to a diode, which prevents
+powering the rest of the board.
+
+![][flash_ic_diode]
+
+Please have a look at the mainboard specific documentation for details.
+
+On those boards it's safe to use a programmer and supply power externally.
+
+**WARNING:** Verify that you apply the correct voltage!
+
+## USB programmer
+USB programmers are usually current limited by the host USB hub. On USB 2.0
+ports the limit is 500mA, which is sufficient to power the flash. Those are
+the best choice as they are stateless and have a fast power on reset cycle.
+
+## Single board computers (like BeagleBone Black / RPi)
+Be careful when connecting a flash chip, especially when using a Pomona
+test-clip. A short circuit or overcurrent (250mA) causes a brown-out reset,
+resulting in a reboot of the running operating system (and possible loss of
+remote shell).
+
+[flash_ic_diode]: flash_ic_diode.svg
diff --git a/Documentation/flash_tutorial/ext_standalone.md b/Documentation/flash_tutorial/ext_standalone.md
new file mode 100644
index 000000000000..3a676ce47ca4
--- /dev/null
+++ b/Documentation/flash_tutorial/ext_standalone.md
@@ -0,0 +1,23 @@
+# Flashing firmware standalone
+
+If none of the other methods work, there are three possibilities:
+
+## Desolder
+You must remove or desolder the flash IC before you can flash it.
+It's recommended to solder a socket in place of the flash IC.
+
+When flashing the IC, always connect all input pins.
+If in doubt, pull /WP, /HOLD, /RESET and alike up towards Vcc.
+
+## SPI flash emulator
+If you are a developer, you might want to use an [EM100Pro] instead, which sets
+the onboard flash on hold, and allows to run custom firmware.
+It provides a very fast development cycle without actually writing to flash.
+
+## SPI flash overwrite
+It is possible to set the onboard flash on hold and use another flash chip.
+Connect all lines one-to-one, except /HOLD. Pull /HOLD of the soldered flash IC
+low, and /HOLD of your replacement flash IC high.
+
+
+[EM100Pro]: https://www.dediprog.com/product/EM100Pro
diff --git a/Documentation/flash_tutorial/flash_ic_diode.svg b/Documentation/flash_tutorial/flash_ic_diode.svg
new file mode 100644
index 000000000000..22cd87277fad
--- /dev/null
+++ b/Documentation/flash_tutorial/flash_ic_diode.svg
@@ -0,0 +1,61 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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+      <tspan x="348.75" y="457.909">VCC</tspan>
+    </text>
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+      <tspan x="345.752" y="463.247">HOLD</tspan>
+    </text>
+    <line style="fill: none; fill-opacity:0; stroke-width: 0.2; stroke: #000000" x1="346.652" y1="459.159" x2="358.402" y2="459.159"/>
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+      <tspan x="349.752" y="468.247">CLK</tspan>
+    </text>
+    <text font-size="4.51549" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="353.502" y="472.997">
+      <tspan x="353.502" y="472.997">DI</tspan>
+    </text>
+    <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #000000" x1="313.49" y1="456.922" x2="322.143" y2="456.922"/>
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+      <tspan x="323.752" y="458.372">CS</tspan>
+    </text>
+    <text font-size="4.51549" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="324.127" y="468.497">
+      <tspan x="324.127" y="468.497">WP</tspan>
+    </text>
+    <text font-size="4.51549" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="323.752" y="472.997">
+      <tspan x="323.752" y="472.997">GND</tspan>
+    </text>
+    <text font-size="4.51549" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="324.127" y="463.497">
+      <tspan x="324.127" y="463.497">DO</tspan>
+    </text>
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diff --git a/Documentation/flash_tutorial/flash_ic_no_diode.svg b/Documentation/flash_tutorial/flash_ic_no_diode.svg
new file mode 100644
index 000000000000..543c9262df53
--- /dev/null
+++ b/Documentation/flash_tutorial/flash_ic_no_diode.svg
@@ -0,0 +1,55 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.0//EN" "http://www.w3.org/TR/2001/PR-SVG-20010719/DTD/svg10.dtd">
+<svg width="4cm" height="3cm" viewBox="311 435 65 45" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
+  <g>
+    <g>
+      <rect style="fill: #ffffff" x="322.124" y="451.034" width="37.75" height="26.6444"/>
+      <rect style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #000000" x="322.124" y="451.034" width="37.75" height="26.6444"/>
+      <text font-size="4.51556" style="fill: #000000;text-anchor:middle;font-family:sans-serif;font-style:normal;font-weight:normal" x="340.999" y="465.734">
+        <tspan x="340.999" y="465.734"></tspan>
+      </text>
+    </g>
+    <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #000000" x1="359.874" y1="456.784" x2="368.528" y2="456.784"/>
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+      <tspan x="348.75" y="457.91">VCC</tspan>
+    </text>
+    <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #000000" x1="359.762" y1="461.772" x2="368.652" y2="461.784"/>
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+      <tspan x="345.752" y="463.246">HOLD</tspan>
+    </text>
+    <line style="fill: none; fill-opacity:0; stroke-width: 0.2; stroke: #000000" x1="346.652" y1="459.16" x2="358.402" y2="459.16"/>
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+      <tspan x="349.752" y="468.246">CLK</tspan>
+    </text>
+    <text font-size="4.51556" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="353.502" y="472.996">
+      <tspan x="353.502" y="472.996">DI</tspan>
+    </text>
+    <line style="fill: none; fill-opacity:0; stroke-width: 1; stroke: #000000" x1="313.49" y1="456.922" x2="322.142" y2="456.922"/>
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+      <tspan x="323.752" y="458.372">CS</tspan>
+    </text>
+    <text font-size="4.51556" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="324.128" y="468.496">
+      <tspan x="324.128" y="468.496">WP</tspan>
+    </text>
+    <text font-size="4.51556" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="323.752" y="472.996">
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+    </text>
+    <text font-size="4.51556" style="fill: #000000;text-anchor:start;font-family:sans-serif;font-style:normal;font-weight:normal" x="324.128" y="463.496">
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diff --git a/Documentation/flash_tutorial/index.md b/Documentation/flash_tutorial/index.md
new file mode 100644
index 000000000000..1a291372a6b3
--- /dev/null
+++ b/Documentation/flash_tutorial/index.md
@@ -0,0 +1,105 @@
+# Flashing firmware tutorial
+
+Updating the firmware is possible using the **internal method**, where the updates
+happen from a running system, or using the **external method**, where the system
+is in a shut down state and an external programmer is attached to write into the
+flash IC.
+
+## Contents
+
+* [Flashing internaly](int_flashrom.md)
+* [Flashing firmware standalone](ext_standalone.md)
+* [Flashing firmware externally supplying direct power](ext_power.md)
+* [Flashing firmware externally without supplying direct power](no_ext_power.md)
+
+## General advice
+
+* It's recommended to only flash the BIOS region.
+* Always verify the firmware image.
+* If you flash externally and have transmission errors:
+  * Use short wires
+  * Reduce clock frequency
+  * Check power supply
+  * Make sure that there are no other bus masters (EC, ME, SoC, ...)
+
+## Internal method
+
+This method using [flashrom] is available on many platforms, as long as they
+aren't locked down.
+
+There are various protection schemes that make it impossible to modify or
+replace a firmware from a running system. coreboot allows to disable these
+mechanisms, making it possible to overwrite (or update) the firmware from a
+running system.
+
+Usually you must use the **external method** once to install a retrofitted
+coreboot and then you can use the **internal method** for future updates.
+
+There are multiple ways to update the firmware:
+* Using flashrom's *internal* programmer to directly write into the firmware
+  flash IC, running on the target machine itself
+* A proprietary software to update the firmware, running on the target machine
+  itself
+* A UEFI firmware update capsule
+
+More details on flashrom's
+* [internal programmer](int_flashrom.md)
+
+## External method
+
+External flashing is possible on many platforms, but requires disassembling
+the target hardware. You need to buy a flash programmer, that
+exposes the same interface as your flash IC (likely SPI).
+
+Please also have a look at the mainboard-specific documentation for details.
+
+After exposing the firmware flash IC, read the schematics and use one of the
+possible methods:
+
+* [Flashing firmware standalone](ext_standalone.md)
+* [Flashing firmware externally supplying direct power](ext_power.md)
+* [Flashing firmware externally without supplying direct power](no_ext_power.md)
+
+**WARNING:** Using the wrong method or accidentally using the wrong pinout might
+  permanently damage your hardware!
+
+## Using a layout file
+On platforms where the flash IC is shared with other components you might want
+to write only a part of the flash IC. On Intel for example there are IFD, ME and
+GBE which don't need to be updated to install coreboot.
+To make [flashrom] only write the *bios* region, leaving Intel ME and Intel IFD
+untouched, you can use a layout file, which can be created using ifdtool
+
+```bash
+ifdtool -f rom.layout coreboot.rom
+```
+
+and looks similar to:
+
+```
+00000000:00000fff fd
+00500000:00bfffff bios
+00003000:004fffff me
+00001000:00002fff gbe
+```
+
+By specifying *-l* and *-i* [flashrom] writes a single region:
+```bash
+flashrom -l rom.layout -i bios -w coreboot.rom -p <programmer>
+```
+
+## Using an IFD to determine the layout
+flashrom version 1.0 supports reading the layout from the IFD (first 4KiB of
+the ROM). You don't need to manually specify a layout it, but it only works
+under the following conditions:
+
+* Only available on Intel ICH7+
+* There's only one flash IC when flashing externally
+
+```bash
+flashrom --ifd -i bios -w coreboot.rom -p <programmer>
+```
+
+**TODO** explain FMAP regions, normal/fallback mechanism, flash lock mechanisms
+
+[flashrom]: https://www.flashrom.org/Flashrom
diff --git a/Documentation/flash_tutorial/int_flashrom.md b/Documentation/flash_tutorial/int_flashrom.md
new file mode 100644
index 000000000000..28b534b003ea
--- /dev/null
+++ b/Documentation/flash_tutorial/int_flashrom.md
@@ -0,0 +1,19 @@
+# Flashing firmware internally
+
+**WARNING:** If you flash a broken firmware and have no recovery mechanism, you
+             must use the **external method** to flash a working firmware again.
+
+## Using flashrom
+This method does only work on Linux, if it isn't locked down.
+You may also need to boot with 'iomem=relaxed' in the kernel command
+line if CONFIG_IO_STRICT_DEVMEM is set.
+
+
+For more details please also check [flashrom's wiki].
+Use the programmer *internal* to flash *coreboot.rom* internally:
+
+```bash
+flashrom -p internal -w coreboot.rom
+```
+
+[flashrom's wiki]: https://www.flashrom.org/Flashrom
diff --git a/Documentation/flash_tutorial/no_ext_power.md b/Documentation/flash_tutorial/no_ext_power.md
new file mode 100644
index 000000000000..b97ba4cc7a1f
--- /dev/null
+++ b/Documentation/flash_tutorial/no_ext_power.md
@@ -0,0 +1,22 @@
+# Flashing firmware externally supplying no power
+
+On some mainboards the flash IC's Vcc pin is connected to the internal
+power-rail, powering the entire board if the flash IC is powered externally.
+Likely it powers other chips which access the flash IC, preventing the external
+programmer from reading/writing the chip. It also violates the components'
+power sequence, bringing the ICs into an undefined state.
+
+![][flash_ic_no_diode]
+
+Please have a look at the mainboard specific documentation for details.
+
+On those boards it's recommended to use a programmer without supplying power
+externally.
+
+The key to read and write the flash IC is to put the machine into *S3* sleep-
+state or *S5* sleep-state *maybe* with Wake-On-LAN enabled.
+Another option that sometimes works is to keep the device in reset. This method requires
+knowledge of the board schematics and might require hardware modifications.
+Use a multimeter to make sure the flash IC is powered in those sleep states.
+
+[flash_ic_no_diode]: flash_ic_no_diode.svg