linux-kernel - Re: [PATCH] arm64: dts: sdm845: Add iommus property to qup1

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Date:   Wed, 5 Jun 2019 10:25:26 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Bjorn Andersson <bjorn.andersson@...aro.org>,
        Andy Gross <agross@...nel.org>,
        open list <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Sibi Sankar <sibis@...eaurora.org>
Subject: Re: [PATCH] arm64: dts: sdm845: Add iommus property to qup1

On Wed, Jun 5, 2019 at 4:16 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Bjorn Andersson (2019-06-04 15:37:00)
> > On Tue 04 Jun 15:29 PDT 2019, Stephen Boyd wrote:
> >
> > > The SMMU that sits in front of the QUP needs to be programmed properly
> > > so that the i2c geni driver can allocate DMA descriptors. Failure to do
> > > this leads to faults when using devices such as an i2c touchscreen where
> > > the transaction is larger than 32 bytes and we use a DMA buffer.
> > >
> >
> > I'm pretty sure I've run into this problem, but before we marked the
> > smmu bypass_disable and as such didn't get the fault, thanks.
> >
> > >  arm-smmu 15000000.iommu: Unexpected global fault, this could be serious
> > >  arm-smmu 15000000.iommu:         GFSR 0x00000002, GFSYNR0 0x00000002, GFSYNR1 0x000006c0, GFSYNR2 0x00000000
> > >
> > > Add the right SID and mask so this works.
> > >
> > > Cc: Sibi Sankar <sibis@...eaurora.org>
> > > Signed-off-by: Stephen Boyd <swboyd@...omium.org>
> > > ---
> > >  arch/arm64/boot/dts/qcom/sdm845.dtsi | 1 +
> > >  1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/arm64/boot/dts/qcom/sdm845.dtsi b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > index fcb93300ca62..2e57e861e17c 100644
> > > --- a/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/sdm845.dtsi
> > > @@ -900,6 +900,7 @@
> > >                       #address-cells = <2>;
> > >                       #size-cells = <2>;
> > >                       ranges;
> > > +                     iommus = <&apps_smmu 0x6c0 0x3>;
> >
> > According to the docs this stream belongs to TZ, the HLOS stream should
> > be 0x6c3.
>
> Aye, I saw this line in the downstream kernel but it doesn't work for
> me. If I specify <&apps_smmu 0x6c3 0x0> it still blows up. I wonder if
> my firmware perhaps is missing some initialization here to make the QUP
> operate in HLOS mode? Otherwise, I thought that the 0x3 at the end was
> the mask and so it should be split off to the second cell in the DT
> specifier but that seemed a little weird.

Two things here -
0x6c0 - TZ SID. Do you see above fault on MTP sdm845 devices?
0x6c3/0x6c6 - HLOS SIDs.

Cheza will throw faults for anything that is programmed with TZ on mtp
as all of that should be handled in HLOS. The firmwares of all these
peripherals assume that the SID reservation is done (whether in TZ or HLOS).

I am inclined to moving the iommus property for all 'TZ' to board dts files.
MTP wouldn't need those SIDs. So, the SOC level dtsi will have just the
HLOS SIDs.

P.S.
As you rightly said, the second cell in iommus property is the mask so that
the iommu is able to reserve all that SIDs that are covered with the
starting SID
and the mask.


Best regards
Vivek
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