linux-kernel - Re: [PATCH] irqchip/gic-v3-its: remove the shareability of ITS

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Date:   Thu, 8 Dec 2022 10:28:29 +0800
From:   Harry Song <jundongsong1@...il.com>
To:     Marc Zyngier <maz@...nel.org>
Cc:     tglx@...utronix.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] irqchip/gic-v3-its: remove the shareability of ITS

On Wed, Dec 7, 2022 at 11:19 PM Marc Zyngier <maz@...nel.org> wrote:
>
> On Wed, 07 Dec 2022 13:52:23 +0000,
> Harry Song <jundongsong1@...il.com> wrote:
> >
> > I know this is a very wrong patch, but my platform
> > has an abnormal ITS problem caused by data consistency:
> > My chip does not support Cache Coherent Interconnect (CCI).
>
> That doesn't mean much. Nothing mandates to have a CCI, and plenty of
> systems have other ways to maintain coherency.
>
> > By default, ITS driver is the inner memory attribute.
> > gits_write_cbaser() is used to write the inner memory
> > attribute. But hw doesn't return the hardware's non-shareable
> > property,so I don't think reading GITS_CBASER and GICR_PROPBASER
> > here will get the real property of the current hardware: inner
> > or outer shareable is not supported, so I would like to know
> > whether ITS driver cannot be used on chips without CCI, or
> > what method can be used to use ITS driver on chips without CCI?
>
> It's not about CCI or not CCI. It is about which shareability domain
> your ITS is in.
>
> And it doesn't only affect the ITS. It also affects the
> redistributors, and anything that accesses memory.
>

Yes, my current chip is Rockchip platform (rk3588), so is it because the chip
is not designed as a proper shared domain for ITS, so the exception of
ITS is caused?

> >
> > The current patch is designed to make ITS think that the current
> > chip has no inner or outer memory properties, and then use
> > its by flushing dcache.
> >
> > This is the log for bug reports without patches:
> >
> > [    0.000000] GICv3: CPU0: found redistributor 0 region 0:0x0000000003460000
> > [    0.000000] ITS [mem 0x03440000-0x0345ffff]
> > [    0.000000] ITS@...000000003440000: allocated 8192 Devices @41850000 (indirect, esz 8, psz 64K, shr 0)
> > [    0.000000] ITS@...000000003440000: allocated 32768 Interrupt Collections @41860000 (flat, esz 2, psz 64K, shr 0)
> > [    0.000000] GICv3: using LPI property table @0x0000000041870000
> > [    0.000000] GICv3: CPU0: using allocated LPI pending table @0x0000000041880000
> > [    0.000000] ITS queue timeout (64 1)
> > [    0.000000] ITS cmd its_build_mapc_cmd failed
> > [    0.000000] ITS queue timeout (128 1)
> > [    0.000000] ITS cmd its_build_invall_cmd failed
>
> Ah, this suspiciously looks like a Rockchip machine...
>
> >
> > Signed-off-by: Harry Song <jundongsong1@...il.com>
> > ---
> >
> > I am very sorry to bother you. This problem has been bothering me
> > for several weeks.  I am looking forward to your reply.
>
> If you have such issue, this needs to be handled as per-platform
> quirk. I'm not putting such generic hacks in the driver.
>
>         M.
>
> --
> Without deviation from the norm, progress is not possible.

Are there currently other chip platforms that have this problem, and then ITS
is already compatible with the problem? Please tell me how to submit
hacks patch for rk3588 platform?

If the hacks patch cannot be submitted, please tell me whether it
requires the next generation
chip to have any design requirements for ITS?

Design ITS and CPU to be the same inner memory property?


Thank you very much for your answer,
Harry