Re: [BUG] rockpro64: PCI BAR reassignment broken by commit 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit memory addresses")

[Peter Geis <pgwipeout@gmail.com>]

On Tue, May 25, 2021 at 9:57 AM Ard Biesheuvel <ardb@kernel.org> wrote:
>
> On Tue, 25 May 2021 at 15:42, Punit Agrawal <punitagrawal@gmail.com> wrote:
> >
> > Hi Ard,
> >
> > Ard Biesheuvel <ardb@kernel.org> writes:
> >
> > > On Sun, 23 May 2021 at 13:06, Punit Agrawal <punitagrawal@gmail.com> wrote:
> > >>
> > >> Robin Murphy <robin.murphy@arm.com> writes:
> > >>
> > >> > [ +linux-pci for visibility ]
> > >> >
> > >> > On 2021-05-18 10:09, Alexandru Elisei wrote:
> > >> >> After doing a git bisect I was able to trace the following error when booting my
> > >> >> rockpro64 v2 (rk3399 SoC) with a PCIE NVME expansion card:
> > >> >> [..]
> > >> >> [    0.305183] rockchip-pcie f8000000.pcie: host bridge /pcie@f8000000 ranges:
> > >> >> [    0.305248] rockchip-pcie f8000000.pcie:      MEM 0x00fa000000..0x00fbdfffff ->
> > >> >> 0x00fa000000
> > >> >> [    0.305285] rockchip-pcie f8000000.pcie:       IO 0x00fbe00000..0x00fbefffff ->
> > >> >> 0x00fbe00000
> > >> >> [    0.306201] rockchip-pcie f8000000.pcie: supply vpcie1v8 not found, using dummy
> > >> >> regulator
> > >> >> [    0.306334] rockchip-pcie f8000000.pcie: supply vpcie0v9 not found, using dummy
> > >> >> regulator
> > >> >> [    0.373705] rockchip-pcie f8000000.pcie: PCI host bridge to bus 0000:00
> > >> >> [    0.373730] pci_bus 0000:00: root bus resource [bus 00-1f]
> > >> >> [    0.373751] pci_bus 0000:00: root bus resource [mem 0xfa000000-0xfbdfffff 64bit]
> > >> >> [    0.373777] pci_bus 0000:00: root bus resource [io  0x0000-0xfffff] (bus
> > >> >> address [0xfbe00000-0xfbefffff])
> > >> >> [    0.373839] pci 0000:00:00.0: [1d87:0100] type 01 class 0x060400
> > >> >> [    0.373973] pci 0000:00:00.0: supports D1
> > >> >> [    0.373992] pci 0000:00:00.0: PME# supported from D0 D1 D3hot
> > >> >> [    0.378518] pci 0000:00:00.0: bridge configuration invalid ([bus 00-00]),
> > >> >> reconfiguring
> > >> >> [    0.378765] pci 0000:01:00.0: [144d:a808] type 00 class 0x010802
> > >> >> [    0.378869] pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x00003fff 64bit]
> > >> >> [    0.379051] pci 0000:01:00.0: Max Payload Size set to 256 (was 128, max 256)
> > >> >> [    0.379661] pci 0000:01:00.0: 8.000 Gb/s available PCIe bandwidth, limited by
> > >> >> 2.5 GT/s PCIe x4 link at 0000:00:00.0 (capable of 31.504 Gb/s with 8.0 GT/s PCIe
> > >> >> x4 link)
> > >> >> [    0.393269] pci_bus 0000:01: busn_res: [bus 01-1f] end is updated to 01
> > >> >> [    0.393311] pci 0000:00:00.0: BAR 14: no space for [mem size 0x00100000]
> > >> >> [    0.393333] pci 0000:00:00.0: BAR 14: failed to assign [mem size 0x00100000]
> > >> >> [    0.393356] pci 0000:01:00.0: BAR 0: no space for [mem size 0x00004000 64bit]
> > >> >> [    0.393375] pci 0000:01:00.0: BAR 0: failed to assign [mem size 0x00004000 64bit]
> > >> >> [    0.393397] pci 0000:00:00.0: PCI bridge to [bus 01]
> > >> >> [    0.393839] pcieport 0000:00:00.0: PME: Signaling with IRQ 78
> > >> >> [    0.394165] pcieport 0000:00:00.0: AER: enabled with IRQ 78
> > >> >> [..]
> > >> >> to the commit 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to
> > >> >> resource flags for
> > >> >> 64-bit memory addresses").
> > >> >
> > >> > FWFW, my hunch is that the host bridge advertising no 32-bit memory
> > >> > resource, only only a single 64-bit non-prefetchable one (even though
> > >> > it's entirely below 4GB) might be a bit weird and tripping something
> > >> > up in the resource assignment code. It certainly seems like the thing
> > >> > most directly related to the offending commit.
> > >> >
> > >> > I'd be tempted to try fiddling with that in the DT (i.e. changing
> > >> > 0x83000000 to 0x82000000 in the PCIe node's "ranges" property) to see
> > >> > if it makes any difference. Note that even if it helps, though, I
> > >> > don't know whether that's the correct fix or just a bodge around a
> > >> > corner-case bug somewhere in the resource code.
> > >>
> > >> From digging into this further the failure seems to be due to a mismatch
> > >> of flags when allocating resources in pci_bus_alloc_from_region() -
> > >>
> > >>     if ((res->flags ^ r->flags) & type_mask)
> > >>             continue;
> > >>
> > >> Though I am also not sure why the failure is only being reported on
> > >> RK3399 - does a single 64-bit window have anything to do with it?
> > >>
> > >
> > > The NVMe in the example exposes a single 64-bit non-prefetchable BAR.
> > > Such BARs can not be allocated in a prefetchable host bridge window
> > > (unlike the converse, i.e., allocating a prefetchable BAR in a
> > > non-prefetchable host bridge window is fine)
> > >
> > > 64-bit non-prefetchable host bridge windows cannot be forwarded by PCI
> > > to PCI bridges, they simply lack the BAR registers to describe them.
> > > Therefore, non-prefetchable endpoint BARs (even 64-bit ones) need to
> > > be carved out of a host bridge's non-prefetchable 32-bit window if
> > > they need to pass through a bridge.
> >
> > Thank you for the explanation. I also looked at the PCI-to-PCI Bridge
> > spec to understand where some of the limitations are coming from.
> >
> > > So the error seems to be here that the host bridge's 32-bit
> > > non-prefetchable window has the 64-bit attribute set, even though it
> > > resides below 4 GB entirely. I suppose that the resource allocation
> > > could be made more forgiving (and it was in the past, before commit
> > > 9d57e61bf723 was applied). However, I would strongly recommend not
> > > deviating from common practice, and just describe the 32-bit
> > > addressable non-prefetchable resource window as such.
> >
> > IIUC, the host bridge's configuration (64-bit on non-prefetchable
> > window) is based on what the hardware advertises.
> >
>
> What do you mean by 'what the hardware advertises'? The host bridge is
> apparently configured to decode a 32-bit addressable window as MMIO,
> and the question is why this window has the 64-bit attribute set in
> the DT description.
>
> > Can you elaborate on what you have in mind to correct the
> > non-prefetchable resource window? Are you thinking of adding a quirk
> > somewhere to address this?
> >
>
> No. Just fix the DT.

Good Morning,

I believe Robin is correct that there is more to this.
While attempting to work out why dGPUs won't work with the rk356x
series PCIe controllers, Christian König from the amd-gpu driver
mailing list noticed the gpu was incorrectly allocated a 64bit
non-prefetchable BAR which should instead be a 32 non-prefetchable
BAR.

The ranges currently set are:
ranges = <0x81000000 0x0 0x00800000 0x3 0x00800000 0x0 0x00100000
0x82000000 0x0 0x00900000 0x3 0x00900000 0x0 0x3f700000>;

but the final allocation was:

lspci -v
00:00.0 PCI bridge: Fuzhou Rockchip Electronics Co., Ltd Device 3566
(rev 01) (prog-if 00 [Normal decode])
        Flags: bus master, fast devsel, latency 0, IRQ 96
        Bus: primary=00, secondary=01, subordinate=ff, sec-latency=0
        I/O behind bridge: 00001000-00001fff [size=4K]
        Memory behind bridge: 00900000-009fffff [size=1M]
        Prefetchable memory behind bridge:
0000000010000000-000000001fffffff [size=256M]
        Expansion ROM at 300a00000 [virtual] [disabled] [size=64K]
        Capabilities: [40] Power Management version 3
        Capabilities: [50] MSI: Enable+ Count=1/32 Maskable- 64bit+
        Capabilities: [70] Express Root Port (Slot-), MSI 00
        Capabilities: [b0] MSI-X: Enable- Count=1 Masked-
        Capabilities: [100] Advanced Error Reporting
        Capabilities: [148] Secondary PCI Express
        Capabilities: [160] L1 PM Substates
        Capabilities: [170] Vendor Specific Information: ID=0002 Rev=4
Len=100 <?>
        Kernel driver in use: pcieport

01:00.0 VGA compatible controller: Advanced Micro Devices, Inc.
[AMD/ATI] Turks PRO [Radeon HD 7570] (prog-if 00 [VGA controller])
        Subsystem: Dell Turks PRO [Radeon HD 7570]
        Flags: bus master, fast devsel, latency 0, IRQ 95
        Memory at 310000000 (64-bit, prefetchable) [size=256M]
        Memory at 300900000 (64-bit, non-prefetchable) [size=128K]
        I/O ports at 1000 [size=256]
        Expansion ROM at 300920000 [disabled] [size=128K]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable- Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1
Len=010 <?>
        Capabilities: [150] Advanced Error Reporting
        Kernel driver in use: radeon

01:00.1 Audio device: Advanced Micro Devices, Inc. [AMD/ATI] Turks
HDMI Audio [Radeon HD 6500/6600 / 6700M Series]
        Subsystem: Dell Turks HDMI Audio [Radeon HD 6500/6600 / 6700M Series]
        Flags: bus master, fast devsel, latency 0, IRQ 98
        Memory at 300940000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: [50] Power Management version 3
        Capabilities: [58] Express Legacy Endpoint, MSI 00
        Capabilities: [a0] MSI: Enable+ Count=1/1 Maskable- 64bit+
        Capabilities: [100] Vendor Specific Information: ID=0001 Rev=1
Len=010 <?>
        Capabilities: [150] Advanced Error Reporting
        Kernel driver in use: snd_hda_intel

This will obviously clobber registers during writes.
Also, if <0x82000000> (32 bit) is changed to <0x83000000> (64 bit),
most of the allocations for the dGPU fail due to no valid regions
available.

>
> > I am happy to put something together once I understand the preferred way
> > to go about it.
> >
> > Thanks,
> > Punit
> >
> > [...]
> >
>
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