[meta-intel] [PATCH 1/1] README: Documentation of hardware features

[nitin.a.kamble at intel.com]

From: Nitin A Kamble <nitin.a.kamble at intel.com>

Starting a new documentation section to describe the layer specific hardware
features. At this point the intel-ucode machine feature is described here.
In the future more such features will be described in this section.

Signed-off-by: Nitin A Kamble <nitin.a.kamble at intel.com>
---
 README | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 75 insertions(+)

diff --git a/README b/README
index c829fdb..f633f36 100644
--- a/README
+++ b/README
@@ -83,3 +83,78 @@ The meta-intel maintainers will do their best to review and/or pull in
 a patch or patchset within 24 hours of the time it was posted.  For
 larger and/or more involved patches and patchsets, the review process
 may take longer.
+
+
+Machine Features in the meta-intel layer
+========================================
+
+Many machine features are available in the oecore/poky layer for BSP use.
+The meta-intel layer makes some additional machine features available for BSPs
+using the meta-intel layer.
+
+Requirements
+------------
+
+The additional machine features are only available when the meta-intel layer
+is included in the build config, and the meta-intel.inc file is included in
+the machine configuration of the interested BSP.
+
+To make these features available for your machine, you will need to:
+
+1. have a configuration line as seen below in the bblayers.conf
+	BBLAYERS += "<local path>/meta-intel.git"
+2. have the following line in the machine configuration
+	require conf/machine/include/meta-intel.inc
+
+Once the above requirements are met, then the machine features provided by
+the meta-intel layer will be available for the BSP use.
+
+Available Machine Features
+--------------------------
+
+As of now the meta-intel layer provides the following list of machine features.
+In the future, more machine features may be available in this list.
+
+* intel-ucode
+
+These machine features can be included by listing them in the MACHINE_FEATURES
+variable in the machine configuration file.
+
+Details of the Machine Features
+-------------------------------
+
+* intel-ucode: This feature provides microcode updating support for Intel
+  processors. With the intel-ucode feature, images get complete support for
+  updating the microcode on Intel processors. This feature enables microcode
+  updating at early boot time by placing the microcode data files in the
+  initrd image. It also puts the user land microcode updating tool iucode_tool
+  and the microcode data file in the target images.
+
+  Q. Why to enable this microcode feature?
+  A. Intel releases microcode updates to correct processor behavior as
+     documented in the respective processor specification updates. While
+     the regular approach to getting this microcode update is via a BIOS
+     upgrade, this can be an administrative hassle and not always possible
+     in the field. The intel-ucode feature enables the microcode update
+     capability from the Linux OS. It provides an easy path for upgrading
+     processor microcode without need of changing BIOS. Once the feature
+     is enabled, it is also possible to update the existing images with
+     newer microcode update in the future.
+
+  Q. How to bundle only specific microcodes in the target image?
+  A. The Intel microcode data file released by Intel contains microcode
+     updates for multiple processors. If the BSP image will be running only
+     on a certain kind of processors, then the number of microcodes bundled in
+     the target image can be filtered by specifying the UCODE_FILTER_SIGNATURES
+     variable. A sequence of iucode-tool parameters are listed in the
+     UCODE_FILTER_SIGNATURES variable to filter the microcodes from the
+     microcode data file. For more information on these parameters refer to
+     the iucode-tool manual page, which can be seen over here:
+       http://manned.org/iucode-tool
+
+  Q. When to not enable this microcode feature?
+  A. The microcode datafile and the associated tools take small (few KB)
+     space on the target image. The BSPs which are highly sensitive to the
+     target image size, which are not experiencing any microcode related issues,
+     may consider not enabling this feature to save the target image foot print.
+
-- 
1.8.1.4