Thanks a lot for your pointers! I am going to try all of them especially DDI_HDMI_Buffer_Translation override.
> interesting. AFAIR, you are the first to ask about integrating it somewhere else :) I am sorry I just I assumed that I can use the library for internal development. The pre-OS graphics driver that I wrote in C based on information from Skylake PRM is not working so I turned to Libgfx to see what i am missing. I hope thats ok? We can not use libgfxinit in the product that we deliver. On Fri, May 10, 2019 at 2:14 AM Nico Huber <[email protected]> wrote: > Hi, > > On 09.05.19 12:03, [email protected] wrote: > > I am using Libgfxinit built for Skylake platform to enable early > > graphics from within a baremetal application. > > interesting. AFAIR, you are the first to ask about integrating it > somewhere else :) > > > The platform connects to an LCD via HDMI. > > Just to be sure is this a regular external display, or something > embedded? External HDMI displays usually just work. If there is a > signal coming, they pick it up and power on. At least that's my > experience. > > > Enabling debug log in Libgfxinit, I get the following from which it > > seems that the initialization completed successfully but the LCD remains > > powered off (orange light). Is there anything outside of this mode set > > sequence that I need to do to enable the display? > > There might be, I'm not sure. > > First, what is not visible from the log is if you set up the frame- > buffer. The Intel GPU has an MMU called graphics translator table > (GTT). If nothing is mapped at address 0 (which is set in your frame- > buffer config), it might be that the pipe doesn't deliver any pixels > and therefore no signal is delivered. If you haven't done that yet, > have a look at HW.GFX.GMA.Setup_Default_FB(). It sets up a framebuffer > in the preallocated graphics memory (aka. stolen memory). > > Second, there's a hardware option to tweak the HDMI signal. I have > never needed it so far, so it's still hard coded to the default, but > an override is prepared: DDI_HDMI_Buffer_Translation in common/hw-gfx- > gma-config.ads.template). The correct value for your device should be > visible in the VBT (Video BIOS Table for Intel). > > What often helps to debug things is a log of a working program. If > you can boot Linux on your platform, that would be most easy, just > add `drm.debug=0xe` to your kernel command line. And there is > `gfx_test` in the libgfxinit source code (see README.md). It's best > to boot with `i915.modeset=0` to disable the Intel graphics driver, > and control the machine via network or a serial console. > > Hope that helps, > Nico >
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