Re: [PATCH 04/22] arm64: dts: qcom: hamoa: Reserve low IOVA range for Iris

[Dmitry Baryshkov]

On Fri, Aug 07, 2026 at 02:56:27PM +0530, Vikash Garodia wrote:
> 
> On 8/7/2026 2:33 PM, Dmitry Baryshkov wrote:
> > On Fri, Aug 07, 2026 at 01:54:48PM +0530, Vikash Garodia wrote:
> > > From: Daniel J Blueman <daniel@xxxxxxxxx>
> > > 
> > > On X1-family hamoa platforms, the Iris VPU reserves IOVA addresses
> > > below 0x25800000 (600MB), primarily for secure non-pixel buffers. DMA
> > > into that range, from any other stream id would triggers unhandled SMMU
> > > page faults that cause spontaneous device reboots. This is readily
> > > reproduced with one or more browser tabs driving multiple concurrent
> > > video decode streams.
> > > 
> > > Add a reserved-memory IOVA reservation node covering [0, 0x25800000]
> > > and reference it from the Iris node so the IOMMU layer keeps DMA
> > > allocations above that boundary.
> > > 
> > > Link: https://github.com/qualcomm-linux/kernel-topics/issues/1157#issuecomment-4458933574
> > > Fixes: 9065340ac04d ("arm64: dts: qcom: x1e80100: Add IRIS video codec")
> > > Cc: stable@xxxxxxxxxxxxxxx
> > > Signed-off-by: Daniel J Blueman <daniel@xxxxxxxxx>
> > > Signed-off-by: Vikash Garodia <vikash.garodia@xxxxxxxxxxxxxxxx>
> > > ---
> > >   arch/arm64/boot/dts/qcom/hamoa.dtsi | 13 ++++++++++++-
> > >   1 file changed, 12 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm64/boot/dts/qcom/hamoa.dtsi b/arch/arm64/boot/dts/qcom/hamoa.dtsi
> > > index 8a96ea1bdb9c4c409b2af997680d8c13fed0643e..87f424765d513c97b06303bceb75ca9f176d2ace 100644
> > > --- a/arch/arm64/boot/dts/qcom/hamoa.dtsi
> > > +++ b/arch/arm64/boot/dts/qcom/hamoa.dtsi
> > > @@ -666,6 +666,17 @@ smem_mem: smem@ffe00000 {
> > >   			hwlocks = <&tcsr_mutex 3>;
> > >   			no-map;
> > >   		};
> > > +
> > > +		/*
> > > +		 * The Iris VPU reserves IOVA below 0x25800000 (600MB),
> > > +		 * primarily for non-pixel buffers using different Stream IDs.
> > > +		 * DMA into that range triggers unhandled SMMU faults and
> > > +		 * spontaneous reboots, so reserve it to keep IOMMU
> > > +		 * allocations above this boundary.
> > > +		 */
> > > +		iris_iova: iris-iova {
> > > +			iommu-addresses = <&iris 0x0 0x0 0x0 0x25800000>;
> > > +		};
> > >   	};
> > >   	qup_opp_table_100mhz: opp-table-qup100mhz {
> > > @@ -5439,7 +5450,7 @@ &config_noc SLAVE_VENUS_CFG QCOM_ICC_TAG_ACTIVE_ONLY>,
> > >   			interconnect-names = "cpu-cfg",
> > >   					     "video-mem";
> > > -			memory-region = <&video_mem>;
> > > +			memory-region = <&video_mem>, <&iris_iova>;
> > 
> > I don't like the idea of this series, because it _again_ doesn't tell us
> > the truth about the hardware. This typicall ends up with bigger problems
> 
> honestly...thats all the info i have about the vpu hardware that it
> restricts non pixel to DMA from the 0-600MB range. The same i have been
> trying for a year now

You are not honest here. You also know that there are secure streams,
which have to use their own IOMMU SIDs. And some of them, as far as I
remember, also have memory range restrictions.

So, if we land these patches, how do extend it later to account for all
of that?

> 
> https://lore.kernel.org/all/20250627-video_cb-v3-1-51e18c0ffbce@xxxxxxxxxxx/
> 
> > later on, when it starts to affect other bits and pieces.
> > 
> > I don't want to NAK it, but I'd strongly ask to reconsider it.
> > 
> > >   			resets = <&gcc GCC_VIDEO_AXI0_CLK_ARES>;
> > >   			reset-names = "bus";
> > > 
> > > -- 
> > > 2.34.1
> > > 
> > 
> 

-- 
With best wishes
Dmitry