[meta-intel] [PATCH 03/12] README.hardware: Documentation of hardware features

[Darren Hart]

On 10/2/14, 12:16, "Tom Zanussi" <tom.zanussi at intel.com> wrote:

>On Thu, 2014-10-02 at 11:27 -0700, nitin.a.kamble at intel.com wrote:
>> From: Nitin A Kamble <nitin.a.kamble at intel.com>
>> 
>> Starting a new documentation file 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 file.
>> 
>> Signed-off-by: Nitin A Kamble <nitin.a.kamble at intel.com>
>> ---
>>  README.hardware | 88
>>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
>Cc:ing Paul, who had a review comment about this from last time:
>
>https://lists.yoctoproject.org/pipermail/meta-intel/2014-September/002614.
>html

Thanks Tom, yes, I thought Paul's point was valid and needs to be
addressed. It seems to me the layer README is a more appropriate location
for things like new Machine Feature documentation.

--
Darren

>
>Tom
>
>>  1 file changed, 88 insertions(+)
>>  create mode 100644 README.hardware
>> 
>> diff --git a/README.hardware b/README.hardware
>> new file mode 100644
>> index 0000000..e27fb33
>> --- /dev/null
>> +++ b/README.hardware
>> @@ -0,0 +1,88 @@
>> +                    meta-intel Layer Hardware README
>> +                    ================================
>> +
>> +This file gives details about using the meta-intel layer with the
>>machines
>> +supported in the layer. A full list of supported reference target
>>machines
>> +can be found by looking in the following directories:
>> +
>> +   conf/machine/
>> +   meta-*/conf/machine/
>> +   meta-isg/meta-*/conf/machine/
>> +
>> +The information in this file is also applicable to machines such as as
>>minnow
>> +which are defined in separate layers and utilize the meta-intel layer.
>> +
>> +
>> +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.
>> +
>
>
>


-- 
Darren Hart
Intel Open Source Technology Center