Jeff Geerling

Well this is weird... `lspci` is showing nothing after recompiling, and I see: ``` [ 0.865707] brcm-pcie fd500000.pcie: host bridge /scb/pcie@7d500000 ranges: [ 0.865731] brcm-pcie fd500000.pcie: No bus range found...

I keep getting that `[ 1.464096] brcm-pcie fd500000.pcie: link down` after every reboot... switching back to a known-good microSD to make sure I haven't done something bad to the hardware....

After re-allocating 1GB of memory to the PCIe bus again, the device is getting recognized again (phew!), so back to recompiling the kernel the 6th time today.

Sooooo close: Darn, *so close*: ``` $ dmesg | grep radeon [ 0.000000] Linux version 5.4.72-v7l-radeon+ (pi@raspberrypi) (gcc version 8.3.0 (Raspbian 8.3.0-6+rpi1)) #1 SMP Fri Oct 23 22:10:38 BST 2020...

I think we may be out of luck, in this case, as @pelwell [mentions](https://www.raspberrypi.org/forums/viewtopic.php?p=1746705#p1746705) that the spec sheet for the BCM2711 says: > Supports accessing external PCIe configuration space and...

Some good reading here: [PCI BARs and other means of accessing the GPU](https://envytools.readthedocs.io/en/latest/hw/bus/bars.html)

Related: https://github.com/geerlingguy/raspberry-pi-pcie-devices/issues/6 Also, I found out more clues through the grapevine today: > You need to find out if the platform supports a cache coherent PCIe interface. The PCI spec...

Further: > tl;dr - It's not the board, it's the old card. > > Looks like the driver is unable to access the PCI ROM which is required to fetch...

Over in the raspberrypi/linux project, it looks like this commit (https://github.com/raspberrypi/linux/commit/54db4b2fa4d17251c2f6e639f849b27c3b553939) has increased the default BAR allocation to 1GB by default—nice!

`unrelenting.technology` over on my blog [posted](https://www.jeffgeerling.com/comment/12488#comment-12488): > Very interesting that the BAR space is configurable on the Broadcrap SoC. > > You can get around the I/O BAR issue on...