On Wed, Nov 27, 2019 at 08:37:38AM +0100, Gerd Hoffmann wrote:
Hi,
Some Intel PCHs integrate pci uarts which are used for serial port debugging. For compatibility purpose, BIOS implementation may assign 0x3f8 to the pci uart's io bar at PEI stage, later during DXE stage the pci uart's bar is re-assigned to a different address.
What firmware you are running on this hardware? Something tianocore based I guess? Is the code public?
The firmware we're running on is Intel RC(Reference Code) under NDA so we can not share here.
As a result, we can't use the hard coded IO port 0x3f8 in SeaBIOS for debugging. Instead, we need read the port base address from the pci uart's BAR, either an IO BAR, or a 32bit memory BAR.
Ok, but ...
config DEBUG_SERIAL_PCI_BDFdepends on DEBUG_SERIAL_PCI_IO || DEBUG_SERIAL_PCI_MEM32hex "Serial port PCI bus/device/function"... hardcoding the BDF instead isn't that great either. Can't we just find the device while scanning for pci devices?
There might be multiple pci uart devices. So hardcoding the BDF seems to be a only solution. Actually this solution is similar to the port based uart( hard coding the port) and mmio based uart(hard coding the mmio address). Here we hard code the pci BDF.
cheers, Gerd