docs: add disable write protect howto

BUG=b:140551928
BRANCH=none
TEST=read doc

Change-Id: I37409c284a1959c584146e41d3d586785a6683f2
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1816927
Reviewed-by: Wai-Hong Tam <waihong@google.com>

1 files changed, 136 insertions, 0 deletions

diff --git a/docs/ccd_howtos.md b/docs/ccd_howtos.md
index d08e88cfd4..874db1d415 100644
--- a/docs/ccd_howtos.md
+++ b/docs/ccd_howtos.md
@@ -64,6 +64,142 @@ This goes through the steps to connect SuzyQ and start using CCD.
         [Setup CCD] instructions to enable them. Being able to use the cr50
         console is a good enough sign that your Suzyq setup is ok.
 
+---
+## I Just Want to Disable Write Protect
+Cr50 has a couple of ways to remove write protect. The biggest difference in the
+process is whether or not you want to open the case and whether or not you need
+write protect disable to be permanent.
+
+**Opening CCD might require the AP can boot. If you're relying on CCD to recover
+a bricked machine, you may want to do the optional CCD setup steps before
+flashing RO firmware.**
+
+### Process if You're Okay Opening Case
+Cr50 will disable write protect if you remove the battery.
+
+#### Steps
+
+1.  **Open the Case.**
+
+2.  **Remove the battery.** Cr50 disables write protect when the battery is
+    disconnected. On chromeboxes you need to remove the write protect screw.
+
+3.  (bob only) remove the write protect screw. Bob uses cr50 and a write protect
+    screw. Cr50 has to disable write protect and the screw has to be removed for
+    write protect to be disabled.
+
+4.  (optional) Check write protect is disabled from the AP.
+
+                AP > flashrom --wp-status
+
+5.  (optional) Reconnecting the battery will reenable write protect. You can
+    disable SW write protect if you want to be able to rewrite RO firmware
+    without needing to keep the battery disconnected.
+
+                AP > flashrom -p host --wp-disable
+
+6.  **(recommended) Run some basic commands to setup CCD.** It's really easy to
+    open cr50 with the battery removed. You might want to setup CCD while you
+    already have the case open and the battery is disconnected. Doing these
+    extra CCD setup steps may make it easier to recover a bricked device using
+    CCD. These will require SuzyQ.
+
+    *   **Open Cr50** from the AP or Cr50 console. This will happen immediately.
+
+
+                AP > gsctool -a -o
+
+        or
+
+                Cr50 > ccd open
+
+
+
+    *   **Setup capabilities.** This can only be done from the Cr50 console.
+
+        Enable flashing the AP/EC CCD open.
+
+                Cr50 > ccd set OverrideWP Always
+                Cr50 > ccd set FlashAP Always
+                Cr50 > ccd set FlashEC Always
+
+        Enable opening Cr50 without booting the AP.
+
+                Cr50 > ccd set OpenNoDevMode Always
+                Cr50 > ccd set OpenFromUSB Always
+
+### Process With Case Closed
+Full instructions are at [Setup CCD], but here are are the basic steps. If
+you're unsure about a step here you should take a look at the [Setup CCD] doc.
+It goes into a lot more detail.
+
+#### Requirements
+
+*   A [SuzyQ]. Cr50 console access is required to disable write protect.
+*   The device needs to be able to boot.
+*   The GBB\_FLAG\_FORCE\_DEV\_SWITCH\_ON GBB flag is cleared.
+
+#### Steps
+1.  **Open CCD.** Here's the most generic way to open ccd. For the full open
+    options see [Setup CCD].
+
+    *   **[Enter dev mode](case_closed_debugging_cr50.md#enter-dev-mode).**
+        These are clamshell instructions for other types of chromeOS devices
+        refer to the full setup doc.
+
+        *   Boot into recovery by pressing the power button, refresh, and
+            escape.
+
+        *   At the recovery screen press Ctrl+D and enter.
+
+    *   **Use gsctool to open Cr50 from the AP.** Press the power button when
+        prompted. This will take ~5 minutes.
+
+                AP > gsctool -a -o
+
+2.  **[Connect](#How-to-Use-SuzyQ) to the Cr50 console** using SuzyQ or servo
+    v4.
+
+                > minicom -D /dev/ttyUSB0
+
+3.  **Disable write protect** using Cr50 [wp console command].
+
+    cmd to disable until cr50 reboots:
+
+                cr50 > wp disable
+
+    cmd to disable it indefinitely:
+
+                cr50 > wp disable atboot
+
+
+4.  (optional) Check write protect is disabled. ccd open takes the AP out of dev
+    mode, so you can reenter dev mode and check the wp status from the AP or you
+    can use ccd to check.
+
+    From AP (after reentering dev mode):
+
+                AP > flashrom --wp-status
+
+    Using CCD:
+
+                from chroot > flashrom -p raiden_debug_spi:target=AP --wp-status
+
+5.  **(recommended) Setup capabilities**, so you can flash the device or open
+    ccd without being able to boot the AP.
+
+    Make flashing the AP/EC accessible without opening CCD
+
+                Cr50 > ccd set OverrideWP Always
+                Cr50 > ccd set FlashAP Always
+                Cr50 > ccd set FlashEC Always
+
+    Enable opening Cr50 without booting the AP
+
+                Cr50 > ccd set OpenNoDevMode Always
+                Cr50 > ccd set OpenFromUSB Always
+
 [Setup CCD]: ./case_closed_debugging_cr50.md#CCD-Setup
 [sparkfun]: https://www.sparkfun.com/products/14746
 [SuzyQ]: https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/refs/heads/master/docs/ccd.md#suzyq-suzyqable
+[wp console command]: ./case_closed_debugging_cr50.md#WP-control