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

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Date:   Thu, 6 Jun 2019 16:47:16 +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

Hi Stephen,

On Thu, Jun 6, 2019 at 2:27 AM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Vivek Gautam (2019-06-04 21:55:26)
> > 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?
>
> No. I see the above fault on Cheza.

Right, expected.

>
> > 0x6c3/0x6c6 - HLOS SIDs.

My bad, the other SID is 0x6D6.

>
> Why are there two? I see some mentions of GSI mode near these SIDs so
> maybe GSI has to be used for DMA here to get the above two SIDs at the
> IOMMU? Otherwise if we do the non-GSI mode of DMA we're going to use the
> "TZ" SID?

Yea, one for GSI, and the other one for non-GSI DMA. I am unsure at this point
about the use of TZ SID, but i would assume this is the SID that's used by the
qup firmware, and therefore on MTP TZ programs this SID.

>
> >
> > 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.
>
> So you're saying you'd like to have the SID be <&apps_smmu 0x6c3 0x0> in
> the sdm845.dtsi file and then override this on Cheza because our SID is
> different (possibly because we don't use GSI)? Why can't we program the
> SID in Cheza firmware to match the "HLOS" SID of 0x6c3?

Sorry my bad, I missed the overriding part.
May be we add the lists of SIDs in board dts only. So, cheza dts will
have all these SIDs -
<&apps_smmu 0x6c0 0x3>   // for both 0x6c0 (TZ) and 0x6c3 (HLOS)
<&apps_smmu 0x6d6 0x0>   // if we want to use the GSI dma.
and
MTP will have
<&apps_smmu 0x6c3 0x0>
<&apps_smmu 0x6d6 0x0>
WDUT?

>
> >
> > 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.
> >
>
> Well if 0x6c6 is another possibility maybe it should be <&apps_smmu
> 0x6c0 0x7> to cover the 0x6c3 and 0x6c6 SIDs?

The other SID was 0x6D6.

Best regards
Vivek

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