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Hello,

I am trying to use PCI-E serial port with UEFI. Unfortunately I cannot initialize serial port.
I checked with GRUB if it is working and while booted in i386-pc (legacy mode), I can configure serial port and everything works fine. However, when I boot x86_64-efi GRUB it says "serial port isn't found" when I try to access it same way I do under CSM.

I also displayed information about serial port device under EFI shell with `pci` command and it reports "(00) I/O space access enabled: 0", what probably is my problem.
I would like to ask if it is possible to enable I/O space access and use that PCI-E adapter for debugging purposes with EFI bootloader?

Before or after you exit boot services?

Before you exit boot services, you should use the Serial I/O Protocol to access it.

After you exit boot services, you can locate the adapter by enumerating PCI and enable its port-mapped I/O by setting bit 0 of the command register in the device's PCI configuration space.

I use PCIe Serial card for debug WinXP 64-bit on pure UEFI. For debugging (WinDbg) to work, you need:

• the PCIe Serial card must support access Port-Mapped I/O (PMIO) (or maybe MIXED Port-Mapped I/O (PMIO) + Memory-Mapped I/O (MMIO)
• under UEFI Shell you need to set bit 0 of command register in PCI config space e.g. my card has bus dev func 04 00 00:
  
  Code:
  mm 04000004 1 -pci
• debugging must be enabled in the BCD file - for my card I need speed 14400
• kdcom.dll must be patched - instead of the I/O address for COM1 03F8 the PCIe card address - mine has D000
• in WinDbg I need to set the speed to 115200

My card have higher CLK and therefore it must be so 14400 in BCD & 115200 in WinDbg

Read this my topic: I am looking for a PCIe card for WinXP debugging

Legacy BIOS WinDbg success: https://www.wincert.net/forum/topic/18477-i-am-looking-for-a-pcie-card-for-winxp-debugging/?do=findComment&comment=137843
Pure UEFI (CSM Disabled) WinDbg success: https://www.wincert.net/forum/topic/18477-i-am-looking-for-a-pcie-card-for-winxp-debugging/?do=findComment&comment=138077

Edited

I have built a SerialDxe.efi driver that enable I/O access (no need use mm 04000004 1 -pci anymore) but to debug Windows I still have to use baudrate 14400 in BCD and 115200 in Windbg:
SerialDxe.efi driver for my PCIe serial card