打造高通UEFI与Linux Android的完美协同：从入门到进阶

QTI针对UEFI规范使用TianocoreEDK2实现。 它是一种开放源代码实施，可从www.tianocore.org/edk2/获得。 TianoCore EDK II提供了现代，适用于UEFI和PI规范的功能丰富的跨平台固件开发环境。 它具有BSD许可证。

0、高通UEFI由两部分组成 XBL 和 ABL

XBL core contains chipset-specific core protocols (drivers) and core applications (such as
charging)
ABL contains chipset-independent applications such as fastboot

XBL core is part of the non-HLOS boot_images code. ABL is part of the open source Linux
Android source tree on Code Aurora Forum. ABL source is BSD-licensed.

1、高通uefi各个阶段入口函数

SEC: _ModuleEntryPoint in Xblcore\moduleEntryPoint.asm
SEC's C entry point: CEntryPoint
SEC loading DXE: LoadDxeCoreFromFv()
DXE: DxeMain()
BDS: BdsEntry() in Qcommpkg\drivers\bdsdxe\bdsentry.c
2、默认的LA启动应用

DefaultChargerApp = "QcomChargerApp"
DefaultBDSBootApp = "LinuxLoader"

路径：boot_images/QcomPkg/SDM845Pkg/LA/uefiplat.cfg

3、启动应用程序时可以使用哪种API?
1. in XBL source code tree, we can use LaunchAppFromGuidedFv()
2. in linux os loader application, we can use LaunchApp()

4、UEFI/PI specification defined 7 Phases, but how about Linux Android release for 8998?
A: yes, UEFI/PI specification defines 7 phases like: SEC/PEI/DXE/BDS/TSL/RT/AL,
But 8998 LA build is only using SEC, DXE, BDS.

二、uefi 显示库调用顺序

1、bsddxeimage->displaydxe->MDPlib->MDPPlatformlib

2、platform panneldetection->panel intialization->start timing engine or auto refresh->exit bootservices(disable display ->save variables)

3. DisplayDxeInitialize-> MDPSetProperty->Display_Utils_Initialize->CheckTargetPanelSupport-> MDPPlatformConfigure（MDPPlatformLib.c）

三、QcomChargerApp 里面会加载displaydxe驱动，显示应该从这里开始的

EFI_STATUS QcomChargerApp_PostProcessing( VOID )
{
EFI_STATUS Status = EFI_SUCCESS;
EFI_QCOM_DISPLAY_UTILS_PROTOCOL *pDisplayUtilsProtocol = NULL;
EFI_DISPLAY_UTILS_RENDERLOGO_CONFIG RenderLogoCfg = { 0 };

if(!pQcomChargerProtocol)
{
Status = gBS->LocateProtocol( &gQcomChargerProtocolGuid, NULL, (VOID **)&pQcomChargerProtocol );
}

QcomChargerAppEvent_ExitLPM();

Status = QcomChargerAppEvent_ReportStatusCode(gEfiPciIoProtocolGuid, LPM_EXIT);

/* Close timer events */
QcomChargerAppEvent_DisplayTimerEvent(FALSE, FALSE);

/* Ensure charging is enabled when booting from UEFI to HLOS */
Status |= pQcomChargerProtocol->EnableCharging(TRUE);

if(NULL == pDisplayUtilsProtocol)
{
Status |= gBS->LocateProtocol( &gQcomDisplayUtilsProtocolGuid, NULL, (VOID **)&pDisplayUtilsProtocol);
}

if((EFI_SUCCESS == Status) && (pDisplayUtilsProtocol != NULL))
{
RenderLogoCfg.uDisplayId = 0;
RenderLogoCfg.uFlags     = DISPLAY_UTILS_RENDERLOGO_CLEARSCREEN;
RenderLogoCfg.xPosition  = 0;
RenderLogoCfg.yPosition  = 0;
Status |= pDisplayUtilsProtocol->DisplayUtilsRenderLogo(&RenderLogoCfg);
}

return Status;
}