Re: [PATCH 2/6] arm64: dts: qcom: sm8250: add apps_smmu node

[Jonathan Marek]

Hi,

On 5/25/20 5:42 AM, Sai Prakash Ranjan wrote:
> Hi Jonathan,
>
> On 2020-05-24 08:08, Jonathan Marek wrote:
> > Add the apps_smmu node for sm8250. Note that adding the iommus field for
> > UFS is required because initializing the iommu removes the bypass mapping
> > that created by the bootloader.
>
> This statement doesn't seem right, you can just say since the bypass is 
> disabled
> by default now, we need to add this property to enable translation and 
> avoid global faults.

If I use this patch [1] then the UFS iommu property isn't needed. In 
downstream, the identity (bypass?) stream mapping is inherited from the 
bootloader, and UFS is used without any iommu property. Setting 
ARM_SMMU_DISABLE_BYPASS_BY_DEFAULT=n doesn't make it work on its own 
(without the UFS iommu property), so there's more to it than just 
"bypass is disabled by default now".

https://patchwork.kernel.org/patch/11310757/

> > Signed-off-by: Jonathan Marek <jonathan@xxxxxxxx>
> > ---
> > Âarch/arm64/boot/dts/qcom/sm8250.dtsi | 107 +++++++++++++++++++++++++++
> > Â1 file changed, 107 insertions(+)
> >
> > diff --git a/arch/arm64/boot/dts/qcom/sm8250.dtsi
> > b/arch/arm64/boot/dts/qcom/sm8250.dtsi
> > index 2f99c350c287..43c5e48c15e2 100644
> > --- a/arch/arm64/boot/dts/qcom/sm8250.dtsi
> > +++ b/arch/arm64/boot/dts/qcom/sm8250.dtsi
> > @@ -323,6 +323,8 @@ ufs_mem_hc: ufshc@1d84000 {
> >
> > ÂÂÂÂÂÂÂÂÂÂÂÂ power-domains = <&gcc UFS_PHY_GDSC>;
> >
> > +ÂÂÂÂÂÂÂÂÂÂÂ iommus = <&apps_smmu 0x0e0 0>, <&apps_smmu 0x4e0 0>;
> > +
> > ÂÂÂÂÂÂÂÂÂÂÂÂ clock-names =
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "core_clk",
> > ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ "bus_aggr_clk",
> > @@ -428,6 +430,111 @@ tlmm: pinctrl@f100000 {
> > ÂÂÂÂÂÂÂÂÂÂÂÂ wakeup-parent = <&pdc>;
> > ÂÂÂÂÂÂÂÂ };
> >
> > +ÂÂÂÂÂÂÂ apps_smmu: iommu@15000000 {
> > +ÂÂÂÂÂÂÂÂÂÂÂ compatible = "qcom,sdm845-smmu-500", "arm,mmu-500";
>
> This should be qcom,sm8250-smmu-500 and also you need to update the 
> arm-smmu
> binding with this compatible in a separate patch.
>
> -Sai