For normal PHBs IODA PEs are handled on a per-bus basis so all the devices
on that bus will share a PE. Which PE specificly is determined by the location
of the MMIO BARs for the devices on the bus so we can't actually configure the
bus PEs until after MMIO resources are allocated. As a result PEs are currently
configured by pcibios_setup_bridge(), which is called just before the bridge
windows are programmed into the bus' parent bridge. Configuring the bus PE here
causes a few problems:
1. The root bus doesn't have a parent bridge so setting up the PE for the root
bus requires some hacks.
2. The PELT-V isn't setup correctly because pnv_ioda_set_peltv() assumes that
PEs will be configured in root-to-leaf order. This assumption is broken
because resource assignment is performed depth-first so the leaf bridges
are setup before their parents are. The hack mentioned in 1) results in
the "correct" PELT-V for busses immediately below the root port, but not
for devices below a switch.
3. It's possible to break the sysfs PCI rescan feature by removing all
the devices on a bus. When the last device is removed from a PE its
will be de-configured. Rescanning the devices on a bus does not cause
the bridge to be reconfigured rendering the devices on that bus
unusable.
We can address most of these problems by moving the PE setup out of
pcibios_setup_bridge() and into pcibios_bus_add_device(). This fixes 1)
and 2) because pcibios_bus_add_device() is called on each device in
root-to-leaf order so PEs for parent buses will always be configured
before their children. It also fixes 3) by ensuring the PE is
configured before initialising DMA for the device. In the event the PE
was de-configured due to removing all the devices in that PE it will
now be reconfigured when a new device is added since there's no
dependecy on the bridge_setup() hook being called.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200417073508.30356-3-oohall@gmail.com
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