> From: Andy Shevchenko <andy.shevche...@gmail.com> > Date: Thu, 9 Apr 2020 12:06:11 +0300 > > On Thu, Apr 9, 2020 at 2:00 AM Simon Glass <s...@chromium.org> wrote: > > > > At present if reading a BAR returns 0xffffffff (e.g. the device is not > > present) then the value is masked and a different value is returned. > > This makes it harder to detect the problem when debugging. > > If you insisting on the code, you may need to reword the commit > message, at least by removing ambiguous "device not present", because > this is not how PCI spec defines situations when device is not > present.
In addition to that: The 0xffffffff value is an artifact of how x86 systems handle aborted PCI transactions. Other architectures will probably generate a fault of some sorts. It looks like at least some of the pci drivers in u-boot emulate the x86 behaviour but I'm not sure all of them do.