[U-Boot] [PATCH 6/6] x86: Allow disabling IGD on Intel Queensbay

[Bin Meng]

Hi Simon,

On Sat, Oct 3, 2015 at 10:29 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Bin,
>
> On 1 October 2015 at 08:36, Bin Meng <bmeng.cn at gmail.com> wrote:
>> Add a Kconfig option to disable the Integrated Graphics Device (IGD)
>> so that it does not show in the PCI configuration space as a VGA
>> disaplay controller. This gives a chance for U-Boot to run PCI/PCIe
>> based graphics card's VGA BIOS and use that for the graphics console.
>>
>> Signed-off-by: Bin Meng <bmeng.cn at gmail.com>
>>
>> ---
>>
>>  arch/x86/cpu/queensbay/Kconfig            |  8 ++++++++
>>  arch/x86/cpu/queensbay/tnc.c              | 19 +++++++++++++++++++
>>  arch/x86/include/asm/arch-queensbay/tnc.h |  5 +++++
>>  include/configs/crownbay.h                |  1 +
>>  4 files changed, 33 insertions(+)
>
> Acked-by: Simon Glass <sjg at chromium.org>
>
> But do we really want configs for such device-specific things? I
> wonder if device tree would be better. E.g. add 'status = "disabled"'
> in the PCI node.
>

I am not sure if I understand you correctly. To me 'status =
"disabled"' is a generic device binding, and when it comes to PCI
device, how do we define a device is in a 'disabled' state? Is it we
program the COMMAND register to disable bus master, mem and I/O
access? Or we program a chipset-specific register (Intel chipset
normally has such) to make it invisible from PCI configuration space
completely? And as you said, this is really chipset-specific thing, so
I chose to do via a platform-specific configuration macro, instead of
doing such work under a generic bindings ..

[snip]

Regards,
Bin