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

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Message-ID: <5cf6f4bb.1c69fb81.c39da.5496@mx.google.com>
Date:   Tue, 04 Jun 2019 15:46:18 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Andy Gross <agross@...nel.org>, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, Sibi Sankar <sibis@...eaurora.org>
Subject: Re: [PATCH] arm64: dts: sdm845: Add iommus property to qup1

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.