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Date:   Mon, 7 Feb 2022 18:19:16 -0700
From:   dann frazier <dann.frazier@canonical.com>
To:     Rob Herring <robh@kernel.org>
Cc:     Toan Le <toan@os.amperecomputing.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
        Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= <kw@linux.com>,
        Bjorn Helgaas <bhelgaas@google.com>,
        Andrew Murray <amurray@thegoodpenguin.co.uk>,
        =?iso-8859-1?Q?St=E9phane?= Graber <stgraber@ubuntu.com>,
        stable <stable@vger.kernel.org>, PCI <linux-pci@vger.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] PCI: xgene: Fix IB window setup
Message-ID: <YgHFFIRT6E0j9TlX@xps13.dannf>
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On Mon, Feb 07, 2022 at 10:09:31AM -0600, Rob Herring wrote:
> On Sat, Feb 5, 2022 at 3:13 PM dann frazier <dann.frazier@canonical.com> wrote:
> >
> > On Sat, Feb 5, 2022 at 9:05 AM Rob Herring <robh@kernel.org> wrote:
> > >
> > > On Fri, Feb 4, 2022 at 5:01 PM dann frazier <dann.frazier@canonical.com> wrote:
> > > >
> > > > On Mon, Nov 29, 2021 at 11:36:37AM -0600, Rob Herring wrote:
> > > > > Commit 6dce5aa59e0b ("PCI: xgene: Use inbound resources for setup")
> > > > > broke PCI support on XGene. The cause is the IB resources are now sorted
> > > > > in address order instead of being in DT dma-ranges order. The result is
> > > > > which inbound registers are used for each region are swapped. I don't
> > > > > know the details about this h/w, but it appears that IB region 0
> > > > > registers can't handle a size greater than 4GB. In any case, limiting
> > > > > the size for region 0 is enough to get back to the original assignment
> > > > > of dma-ranges to regions.
> > > >
> > > > hey Rob!
> > > >
> > > > I've been seeing a panic on HP Moonshoot m400 cartridges (X-Gene1) -
> > > > only during network installs - that I also bisected down to commit
> > > > 6dce5aa59e0b ("PCI: xgene: Use inbound resources for setup"). I was
> > > > hoping that this patch that fixed the issue on St?phane's X-Gene2
> > > > system would also fix my issue, but no luck. In fact, it seems to just
> > > > makes it fail differently. Reverting both patches is required to get a
> > > > v5.17-rc kernel to boot.
> > > >
> > > > I've collected the following logs - let me know if anything else would
> > > > be useful.
> > > >
> > > > 1) v5.17-rc2+ (unmodified):
> > > >    http://dannf.org/bugs/m400-no-reverts.log
> > > >    Note that the mlx4 driver fails initialization.
> > > >
> > > > 2) v5.17-rc2+, w/o the commit that fixed St?phane's system:
> > > >    http://dannf.org/bugs/m400-xgene2-fix-reverted.log
> > > >    Note the mlx4 MSI-X timeout, and later panic.
> > > >
> > > > 3) v5.17-rc2+, w/ both commits reverted (works)
> > > >    http://dannf.org/bugs/m400-both-reverted.log
> > >
> > > The ranges and dma-ranges addresses don't appear to match up with any
> > > upstream dts files. Can you send me the DT?
> >
> > Sure: http://dannf.org/bugs/fdt
> 
> The first fix certainly is a problem. It's going to need something
> besides size to key off of (originally it was dependent on order of
> dma-ranges entries).
> 
> The 2nd issue is the 'dma-ranges' has a second entry that is now ignored:
> 
> dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00>, <0x00
> 0x79000000 0x00 0x79000000 0x00 0x800000>;
> 
> Based on the flags (3rd addr cell: 0x0), we have an inbound config
> space which the kernel now ignores because inbound config space
> accesses make no sense. But clearly some setup is needed. Upstream, in
> contrast, sets up a memory range that includes this region, so the
> setup does happen:
> 
> <0x42000000 0x00 0x00000000 0x00 0x00000000 0x80 0x00000000>
> 
> Minimally, I suspect it will work if you change dma-ranges 2nd entry to:
> 
> <0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>

Thanks for looking into this Rob. I tried to test that theory, but it
didn't seem to work. This is what I tried:

--- m400.dts	2022-02-07 20:16:44.840475323 +0000
+++ m400.dts.dmaonly	2022-02-08 00:17:54.097132000 +0000
@@ -446,7 +446,7 @@
 			reg = <0x00 0x1f2b0000 0x00 0x10000 0xe0 0xd0000000 0x00 0x200000 0x00 0x79e00000 0x00 0x2000000 0x00 0x79000000 0x00 0x800000>;
 			reg-names = "csr\0cfg\0msi_gen\0msi_term";
 			ranges = <0x1000000 0x00 0x00 0xe0 0x10000000 0x00 0x10000 0x2000000 0x00 0x30000000 0xe1 0x30000000 0x00 0x80000000>;
-			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
+			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges-ep = <0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x79000000 0x00 0x79000000 0x00 0x100000>;
 			interrupts = <0x00 0x10 0x04>;
@@ -471,7 +471,7 @@
 			reg = <0x00 0x1f2c0000 0x00 0x10000 0xd0 0xd0000000 0x00 0x200000 0x00 0x79e00000 0x00 0x2000000 0x00 0x79000000 0x00 0x800000>;
 			reg-names = "csr\0cfg\0msi_gen\0msi_term";
 			ranges = <0x1000000 0x00 0x00 0xd0 0x10000000 0x00 0x10000 0x2000000 0x00 0x30000000 0xd1 0x30000000 0x00 0x80000000>;
-			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
+			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges-ep = <0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x79000000 0x00 0x79000000 0x00 0x100000>;
 			interrupts = <0x00 0x10 0x04>;
@@ -496,7 +496,7 @@
 			reg = <0x00 0x1f2d0000 0x00 0x10000 0x90 0xd0000000 0x00 0x200000 0x00 0x79e00000 0x00 0x2000000 0x00 0x79000000 0x00 0x800000>;
 			reg-names = "csr\0cfg\0msi_gen\0msi_term";
 			ranges = <0x1000000 0x00 0x00 0x90 0x10000000 0x00 0x10000 0x2000000 0x00 0x30000000 0x91 0x30000000 0x00 0x80000000>;
-			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
+			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges-ep = <0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x79000000 0x00 0x79000000 0x00 0x100000>;
 			interrupts = <0x00 0x10 0x04>;
@@ -522,7 +522,7 @@
 			reg = <0x00 0x1f500000 0x00 0x10000 0xa0 0xd0000000 0x00 0x200000 0x00 0x79e00000 0x00 0x2000000 0x00 0x79000000 0x00 0x800000>;
 			reg-names = "csr\0cfg\0msi_gen\0msi_term";
 			ranges = <0x2000000 0x00 0x30000000 0xa1 0x30000000 0x00 0x80000000>;
-			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
+			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges-ep = <0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x79000000 0x00 0x79000000 0x00 0x100000>;
 			interrupts = <0x00 0x10 0x04>;
@@ -547,7 +547,7 @@
 			reg = <0x00 0x1f510000 0x00 0x10000 0xc0 0xd0000000 0x00 0x200000 0x00 0x79e00000 0x00 0x2000000 0x00 0x79000000 0x00 0x800000>;
 			reg-names = "csr\0cfg\0msi_gen\0msi_term";
 			ranges = <0x1000000 0x00 0x00 0xc0 0x10000000 0x00 0x10000 0x2000000 0x00 0x30000000 0xc1 0x30000000 0x00 0x80000000>;
-			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
+			dma-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x42000000 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges = <0x42000000 0x40 0x00 0x40 0x00 0x40 0x00 0x00 0x00 0x79000000 0x00 0x79000000 0x00 0x800000>;
 			ib-ranges-ep = <0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x00 0x00 0x00 0x00 0x400000 0x2000000 0x00 0x79000000 0x00 0x79000000 0x00 0x100000>;
 			interrupts = <0x00 0x10 0x04>;

And that failed to boot with a 5.17-rc3. Since dma-ranges was
previously identical to ib-ranges, I also tried making the same change
to ib-ranges, but with no success.

> While we shouldn't break existing DTs, the moonshot DT doesn't use
> what's documented upstream. There are multiple differences compared to
> what's documented. Is upstream supposed to support upstream DTs,
> downstream DTs, and ACPI for XGene which is an abandoned platform with
> only a handful of users?

That's a fair question, though it's one of a policy, and I feel I'd be
overstepping by weighing in. I suppose one option I have is to try
and create and upstream a dts for these systems and modify our
boot.scr to always load that over the one provided by firmware. While
we do have some of these systems in production, they are being retired
and replaced with newer kit over time, and it's possible we'll never
need to upgrade them to a modern kernel.

  -dann