On Mon, Mar 26, 2018 at 05:12:52PM +0200, Wolfgang Denk wrote: > In message <20180326135235.GA221217@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx> you wrote: > > > > P.S. https://en.wikipedia.org/wiki/Unified_Extensible_Firmware_Interface > > has a little interesting background on UEFI/CSM. > > Thanks for the pointer. > > I start wondering if the mainboard / BIOS vendors stop supporting > such older hardware, if such support could be re-added in Linux? > OK, obviously not for the boot device, but... > > In U-Boot we have an x86 emulator to be able to initialize the > on-board BIOS on (at least some) graphics cards so you can use these > on ARM or Power architecture systems. Do we really have to add > similar stuff to Linux to support legacy hardware? > > Would that even work? On the MSI Z370 Tomahawk and the Gigabyte Z270X Ultra Gaming systems, it looks like you're using what the BIOS designates as "Slot #1", which is below an Intel Root Port (00:01.0 in both cases). When the SAS3444E is in that slot, we don't even see the Root Port itself. To fix that would require Linux to have chipset-specific knowledge about how to enable that Root Port. I guess it's conceivable that could be done, but I don't know if the information required is public. I assume this would be controlled by some MSR or other Intel-specific knob. On the Gigabyte AB350 Gaming system, you're using "Slot #1" (this comes from the Slot Capabilities register and may not match any silk-screened labels on the board). This is below an AMD PCIe switch, where 04:04.0 is the Downstream Port leading to that slot. When the SAS3444E is in the slot, we do see the 04:04.0 Downstream Port, so we *should* still be able to see the SAS device. This is now all in the PCIe domain so the BIOS should be pretty much out of the picture, and I can't explain why we don't see the SAS3444E device. On that system, you could try something like this to reset the SAS3444E device and try to rescan the bus: # setpci -s04:04.0 BRIDGE_CONTROL.w=0x40 # sleep 1 # setpci -s04:04.0 BRIDGE_CONTROL.w=0x00 # sleep 10 # echo 1 > /sys/bus/pci/rescan Check the dmesg log afterwards to see if anything happened.
