Re: [edk2-devel] [PATCH 0/2] MdeModulePkg: Make the screen seamless

["Gao, Zhichao" <zhichao.gao@intel.com>]

> -----Original Message-----
> From: Laszlo Ersek [mailto:lersek@redhat.com]
> Sent: Friday, April 12, 2019 4:06 PM
> To: devel@edk2.groups.io; Gao, Zhichao <zhichao.gao@intel.com>
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Wu, Hao A <hao.a.wu@intel.com>;
> Ni, Ray <ray.ni@intel.com>; Zeng, Star <star.zeng@intel.com>; Gao, Liming
> <liming.gao@intel.com>; Sean Brogan <sean.brogan@microsoft.com>;
> Michael Turner <Michael.Turner@microsoft.com>; Bret Barkelew
> <Bret.Barkelew@microsoft.com>
> Subject: Re: [edk2-devel] [PATCH 0/2] MdeModulePkg: Make the screen
> seamless
> 
> On 04/12/19 05:14, Gao, Zhichao wrote:
> > For now most platforms support display function at PEI phase.
> > But the conspliter and graphics console driver would clear the screen
> > at BDS connect console phase. Maybe some platforms would show logo in
> > the next or maybe not. For consumers, it looks like the screen
> > flashed.
> > So change the behavior of graphics console devices while connect
> > console devices to maintain seamless screen from PEI.
> >
> > Test has done on MinPlatform Kabylake-RVP3 which support PEI display.
> >
> > Cc: Jian J Wang <jian.j.wang@intel.com>
> > Cc: Hao Wu <hao.a.wu@intel.com>
> > Cc: Ray Ni <ray.ni@intel.com>
> > Cc: Star Zeng <star.zeng@intel.com>
> > Cc: Liming Gao <liming.gao@intel.com>
> > Cc: Sean Brogan <sean.brogan@microsoft.com>
> > Cc: Michael Turner <Michael.Turner@microsoft.com>
> > Cc: Bret Barkelew <Bret.Barkelew@microsoft.com>
> >
> > Aaron Antone (2):
> >   MdeModulePkg/ConSplitterDxe: Optimize the
> ConSplitterTextOutSetMode
> >   MdeModulePkg/GraphicsConsoleDxe: Do not clean the screen
> >
> >  .../Console/ConSplitterDxe/ConSplitter.c      | 34 +++++++++-----
> >  .../Console/ConSplitterDxe/ConSplitter.h      |  4 +-
> >  .../GraphicsConsoleDxe/GraphicsConsole.c      | 45 +++++++++----------
> >  3 files changed, 48 insertions(+), 35 deletions(-)
> >
> 
> EFI_GRAPHICS_OUTPUT_PROTOCOL.SetMode() is specified to clear the
> screen to black. Is this series compatible with that?

No. We only consider the console section.
There are two pcds to control the graphics output mode PcdVideoHorizontalResolution and PcdVideoVerticalResolution. Usually we set them as zero to make the mode to be the max mode the graphics supported and the graphics output protocol would initialize the mode to be the max mode in general. If so the SetMode would not  be runt. But that is done in the graphics output driver and the driver is usually a binary file. So we can't desire that the graphics driver  would set the max mode, that is the graphics output driver's vendor decided.
In the other condition, these two pcds would set a value and then graphics output driver would focus to set the mode and clear the screen. That is controlled by the consumer. By default the two pcds is initialized as 800 and 600. Because this resolution may be the most normal resolution and the screen would always be cleared.
 
In my opinion, the behavior of graphics output section in this driver is fine and should not be changed. And also, it is hard for us to control it because the driver is usually not open source.
The upon results are based on kabylake Rvp3 platform. Maybe I missed something. Any incorrect, please feel free to point out.

Thanks,
Zhichao

> 
> Thanks,
> Laszlo