Re: [PATCH v2] arm64: dts: rockchip: rk356x: Fix PCIe register map and ranges

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> From: Peter Geis <pgwipeout@gmail.com>
> Date: Sat, 22 Oct 2022 08:19:57 -0400

Hello Peter,

> On Fri, Oct 21, 2022 at 4:52 PM Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >
> > > Date: Fri, 21 Oct 2022 21:32:48 +0200
> > > From: Ondřej Jirman <megi@xff.cz>
> > >
> > > On Fri, Oct 21, 2022 at 12:48:15PM -0400, Peter Geis wrote:
> > > > On Fri, Oct 21, 2022 at 11:39 AM Ondřej Jirman <megi@xff.cz> wrote:
> > > > >
> > > > > On Fri, Oct 21, 2022 at 09:07:50AM -0400, Peter Geis wrote:
> > > > > > Good Morning Heiko,
> > > > > >
> > > > > > Apologies for just getting to this, I'm still in the middle of moving
> > > > > > and just got my lab set back up.
> > > > > >
> > > > > > I've tested this patch series and it leads to the same regression with
> > > > > > NVMe drives. A loop of md5sum on two identical 4GB random files
> > > > > > produces the following results:
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand.img
> > > > > > fad97e91da8d4fd554c895cafa89809b  test-rand2.img
> > > > > > 2d56a7baa05c38535f4c19a2b371f90a  test-rand.img
> > > > > > 74e8e6f93d7c3dc3ad250e91176f5901  test-rand2.img
> > > > > > 25cfcfecf4dd529e4e9fbbe2be482053  test-rand.img
> > > > > > 74e8e6f93d7c3dc3ad250e91176f5901  test-rand2.img
> > > > > > b9637505bf88ed725f6d03deb7065dab  test-rand.img
> > > > > > f7437e88d524ea92e097db51dce1c60d  test-rand2.img
> > > > > >
> > > > > > Before this patch series:
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand2.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand2.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand2.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand.img
> > > > > > d11cf0caa541b72551ca22dc5bef2de0  test-rand2.img
> > > > > >
> > > > > > Though I do love where this patch is going and would like to see if it
> > > > > > can be made to work, in its current form it does not.
> > > > >
> > > > > Thanks for the test. Can you please also test v1? Also please share lspci -vvv
> > > > > of your nvme drive, so that we can see allocated address ranges, etc.
> > > >
> > > > Good catch, with your patch as is, the following issue crops up:
> > > > Region 0: Memory at 300000000 (64-bit, non-prefetchable) [size=16K]
> > > > Region 2: I/O ports at 1000 [disabled] [size=256]
> > > >
> > > > However, with a simple fix, we can get this:
> > > > Region 0: Memory at 300000000 (64-bit, non-prefetchable) [virtual] [size=16K]
> > > > Region 2: I/O ports at 1000 [virtual] [size=256]
> > > >
> > > > and with it a working NVMe drive.
> > > >
> > > > Change the following range:
> > > > 0x02000000 0x0 0x40000000 0x3 0x00000000 0x0 0x40000000>;
> > > > to
> > > > 0x02000000 0x0 0x00000000 0x3 0x00000000 0x0 0x40000000>;
> > >
> > > I've already tried this, but this unfrotunately breaks the wifi cards.
> > > (those only use the I/O space) Maybe because I/O and memory address spaces
> > > now overlap, I don't know. That's why I used the 1GiB offset for memory
> > > space.
> >
> > Meanwhile, I have an NVMe drive that only works if mmio is completely
> > untranslated.  This is an ADATA SX8000NP drive, which uses a Silicon
> > Motion SM2260 controller.
> >
> > So for me, a working configuration has the following "ranges":
> >
> > ranges = <0x01000000 0x0 0x00000000 0x3 0x3fff0000 0x0 0x00010000>,
> >          <0x02000000 0x0 0xf4000000 0x0 0xf4000000 0x0 0x02000000>,
> >          <0x03000000 0x3 0x10000000 0x3 0x10000000 0x0 0x2fff0000>;
> >
> > This also needs changes to the "reg" propery:
> >
> > reg = <0x3 0xc0000000 0x0 0x00400000>,
> >       <0x0 0xfe260000 0x0 0x00010000>,
> >       <0x3 0x00000000 0x0 0x10000000>;
> 
> Now this is interesting. I've been reading up on PCIe ranges and what
> is necessary for things to work properly, and I found this interesting
> article from ARM:
> https://developer.arm.com/documentation/102337/0000/Programmers-model/Memory-maps/AP-system-memory-map/PCIe-MMIO-and-ECAM-memory-regions
> 
> TLDR: We need a low region (below 4g) and a high region.

Well, that description applies to a specific ARM reference design.
And it appears that the PCIe-RC used in that reference design does not
support address translation.

The Synopsys DesignWare PCIe-RC implementation used on the RockChip
RK35xx SoCs does support address translation.  But some of the results
we're seeing suggests that this feature is subtly broken for the
RockChip implementation.

> >From other articles I've gleaned that the config / io should probably
> also be in the low range. As such I believe the other patch that was
> sent to me may be the correct way to go. If both of you would try the
> following reg / ranges:
> 
> reg = <0x3 0xc0000000 0x0 0x00400000>,
>       <0x0 0xfe260000 0x0 0x00010000>,
>       <0x0 0xf4000000 0x0 0x00100000>;
> 
> ranges = <0x01000000 0x0 0xf4100000 0x0 0xf4100000 0x0 0x00100000>,
> <0x02000000 0x0 0xf4200000 0x0 0xf4200000 0x0 0x01e00000>,
> <0x03000000 0x0 0x40000000 0x3 0x00000000 0x0 0x40000000>;

So that matches the configuration used by RockChip in their downstream
kernel and u-boot:

  https://github.com/rockchip-linux/kernel/blob/develop-5.10/arch/arm64/boot/dts/rockchip/rk3568.dtsi#L2382

That probably means this config has received testing in the wild.

I tried this configuration on my board during my earlier experiments,
and it works.

One downside of this configuration is that it uses 32-bit IO
addresses.  Support for 32-bit IO address is not universal since the
x86 INB and OUTB instructions only support a 16-bit address space.
But if translation is indeed broken for IO in the same way as MMIO,
that might be the best you can do.

> > Now admittedly, this is with OpenBSD running on EDK2 UEFI firmware
> > from
> >
> >   https://github.com/jaredmcneill/quartz64_uefi
> >
> > that I modified to pass through the device tree and modify the ranges
> > as above.  But the way my OpenBSD driver sets up the address
> > translation windows matches what the mainline Linux driver does.
> >
> > I picked the ranges above to match the EDK2 configuration.  But it is
> > a setup that maximizes the 32-bit mmio window.
> >
> > Cheers,
> >
> > Mark
> >
> > > > I still haven't tested this with other cards yet, and another patch
> > > > that does similar work I've tested successfully as well with NVMe
> > > > drives. I'll have to get back to you on the results of greater
> > > > testing.
> > > >
> > > > Very Respectfully,
> > > > Peter Geis
> > > >
> > > > >
> > > > > kind regards,
> > > > >         o.
> > > > >
> > > > > > Very Respectfully,
> > > > > > Peter Geis
> > >
> > > _______________________________________________
> > > linux-arm-kernel mailing list
> > > linux-arm-kernel@lists.infradead.org
> > > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 

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