Message-ID: <CAMj1kXHsGgFedbhW2CiS5gveK3=ZxhXQ5siDeHJyttkOVKBQrQ@mail.gmail.com>
Date:   Tue, 25 May 2021 18:44:19 +0200
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Peter Geis <pgwipeout@...il.com>
Cc:     Punit Agrawal <punitagrawal@...il.com>,
        Robin Murphy <robin.murphy@....com>,
        Alexandru Elisei <alexandru.elisei@....com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        arm-mail-list <linux-arm-kernel@...ts.infradead.org>,
        Heiko Stuebner <heiko.stuebner@...obroma-systems.com>,
        Leonardo Bras <leobras.c@...il.com>,
        Rob Herring <robh@...nel.org>, PCI <linux-pci@...r.kernel.org>,
        Christian König <ckoenig.leichtzumerken@...il.com>
Subject: Re: [BUG] rockpro64: PCI BAR reassignment broken by commit
 9d57e61bf723 ("of/pci: Add IORESOURCE_MEM_64 to resource flags for 64-bit
 memory addresses")

On Tue, 25 May 2021 at 18:23, Peter Geis <pgwipeout@...il.com> wrote:
>
> On Tue, May 25, 2021 at 11:55 AM Ard Biesheuvel <ardb@...nel.org> wrote:
> >
> > On Tue, 25 May 2021 at 17:34, Peter Geis <pgwipeout@...il.com> wrote:
> > >
> > > On Tue, May 25, 2021 at 9:57 AM Ard Biesheuvel <ardb@...nel.org> wrote:
> > > >
> > > > On Tue, 25 May 2021 at 15:42, Punit Agrawal <punitagrawal@...il.com> wrote:
> > > > >
> > > > > Hi Ard,
> > > > >
> > > > > Ard Biesheuvel <ardb@...nel.org> writes:
> > > > >
> > > > > > On Sun, 23 May 2021 at 13:06, Punit Agrawal <punitagrawal@...il.com> wrote:
> > > > > >>
> > > > > >> Robin Murphy <robin.murphy@....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@...00000 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.
> > >
> >
> > This is due to the translation. For some reason, lspci translates the
> > BAR values to CPU addresses, but the PCI side addresses are within
> > 32-bits.
>
> The kernel log reports the same thing:
> [    6.662141] pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x0fffffff
> 64bit pref]
> [    6.662963] pci 0000:01:00.0: reg 0x18: [mem 0x00000000-0x0001ffff 64bit]
>
> You are saying this is a display only issue?
>

Yes. What do the 'root bus resource' log lines say for these regions?
Those should give you both the CPU address as well as the bus address.


> >
> > Are you sure the amdgpu driver can even deal with non-1:1 host bridges?
>
> I cannot answer this as I'm not an amdgpu dev.
>
> >
> > > The ranges currently set are:
> > > ranges = <0x81000000 0x0 0x00800000 0x3 0x00800000 0x0 0x00100000
> > > 0x82000000 0x0 0x00900000 0x3 0x00900000 0x0 0x3f700000>;
> > >
> >
> > So you have two ranges here.
>
> The IO and PCI memory ranges.
>
> There is a third range, the configuration range, which is defined in
> the reg block:
> <0x3 0x00000000 0x0 0x800000>
> All three are shared in the same 1GB window on the rk356x.
>

But the reg block is not a resource window, it is a configuration
range to program the host bridge.

> https://elixir.bootlin.com/linux/v5.13-rc3/source/Documentation/devicetree/bindings/pci/designware-pcie.txt#L12
>
> >
> > > 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]
> >
> > But the host bridge/root port decodes two disjoint regions??
> >
> > >         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.
> >
> > I don't follow. Which writes will clobber which registers, and how is
> > it obvious?
>
> Writing a 64 bit word into a 32 bit register will either clobber the
> next higher 32 bit register.
> Quoting Christian:
> "When you program a 32bit BAR as 64bit you overwrite the register behind
> the BAR address with the upper 32bits of the 64bit address value.
> So even if the allocation fits into 32bits, the extra register write
> will certainly put your device into a banana state."
>
> https://lists.freedesktop.org/archives/amd-gfx/2021-May/064232.html
>

I seriously doubt that this is what is going on here.

lspci -x will give you the bare BAR values - I suspect that those are
probably fine.


> >
> > > 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.
> > >
> >
> > But wasn't the original problem that the resource window was 64-bit to
> > begin with? Are you sure we are talking about the same problem here?
>
> The rk3399 in the original report has a 32MB memory window in the
> upper end of the 4GB range.
> The rk356x has a similar layout, or it can use a 1GB window available
> at <0x3 0x00000000>.
> Rockchip's default windows are defined as 64bit.
>
> The rk3399 doesn't have enough space to reasonably define two windows,
> one 32bit, one 64bit, to work around an allocation bug.
> These are the defined regions in the rk3399:
> ranges = <0x83000000 0x0 0xfa000000 0x0 0xfa000000 0x0 0x1e00000>,
> <0x81000000 0x0 0xfbe00000 0x0 0xfbe00000 0x0 0x100000>;
>

All you really need is a 32-bit non-prefetchable resource window: any
BAR can be allocated from that. A 64-bit BAR can carry a 32-bit number
(just add zeroes at the top), and a prefetchable BAR can happily live
in a non-prefetchable window, with a theoretical performance impact if
the OS actually does use different memory attributes for the
prefetchable window (but I don't think Linux ever handles it this way)


>
> >
> >
> > > >
> > > > > I am happy to put something together once I understand the preferred way
> > > > > to go about it.
> > > > >
> > > > > Thanks,
> > > > > Punit
> > > > >
> > > > > [...]
> > > > >
> > > >
> > > > _______________________________________________
> > > > Linux-rockchip mailing list
> > > > Linux-rockchip@...ts.infradead.org
> > > > http://lists.infradead.org/mailman/listinfo/linux-rockchip

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