linux-kernel - Re: [PATCH 1/6] dt-bindings: remoteproc: qcom,pas-common: Introduce iommus and qcom,devmem property

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Message-ID: <CAA8EJpqay7Nryb5HwwHE1+iiMXKUvqi-djmCsYN8fxigt-s-tQ@mail.gmail.com>
Date: Mon, 7 Oct 2024 18:25:01 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Mukesh Ojha <quic_mojha@...cinc.com>
Cc: Bjorn Andersson <andersson@...nel.org>, Mathieu Poirier <mathieu.poirier@...aro.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Konrad Dybcio <konradybcio@...nel.org>, 
	Bartosz Golaszewski <bartosz.golaszewski@...aro.org>, 
	Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>, linux-arm-msm@...r.kernel.org, 
	linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Shiraz Hashim <quic_shashim@...cinc.com>
Subject: Re: [PATCH 1/6] dt-bindings: remoteproc: qcom,pas-common: Introduce
 iommus and qcom,devmem property

On Mon, 7 Oct 2024 at 17:35, Mukesh Ojha <quic_mojha@...cinc.com> wrote:
>
> On Sun, Oct 06, 2024 at 10:38:01PM +0300, Dmitry Baryshkov wrote:
> > On Sat, Oct 05, 2024 at 02:53:54AM GMT, Mukesh Ojha wrote:
> > > From: Shiraz Hashim <quic_shashim@...cinc.com>
> > >
> > > Qualcomm’s PAS implementation for remote processors only supports a
> > > single stage of IOMMU translation and is presently managed by the
> > > Qualcomm EL2 hypervisor (QHEE) if it is present. In the absence of QHEE,
> > > such as with a KVM hypervisor, IOMMU translations need to be set up by
> > > the KVM host. Remoteproc needs carveout memory region and its resource
> > > (device memory) permissions to be set before it comes up, and this
> > > information is presently available statically with QHEE.
> > >
> > > In the absence of QHEE, the boot firmware needs to overlay this
> > > information based on SoCs running with either QHEE or a KVM hypervisor
> > > (CPUs booted in EL2).
> > >
> > > The qcom,devmem property provides IOMMU devmem translation information
> > > intended for non-QHEE based systems.
> > >
> > > Signed-off-by: Shiraz Hashim <quic_shashim@...cinc.com>
> > > Co-Developed-by: Mukesh Ojha <quic_mojha@...cinc.com>
> > > Signed-off-by: Mukesh Ojha <quic_mojha@...cinc.com>
> > > ---
> > >  .../bindings/remoteproc/qcom,pas-common.yaml  | 42 +++++++++++++++++++
> > >  .../bindings/remoteproc/qcom,sa8775p-pas.yaml | 20 +++++++++
> > >  2 files changed, 62 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/remoteproc/qcom,pas-common.yaml b/Documentation/devicetree/bindings/remoteproc/qcom,pas-common.yaml
> > > index 63a82e7a8bf8..068e177ad934 100644
> > > --- a/Documentation/devicetree/bindings/remoteproc/qcom,pas-common.yaml
> > > +++ b/Documentation/devicetree/bindings/remoteproc/qcom,pas-common.yaml
> > > @@ -52,6 +52,48 @@ properties:
> > >      minItems: 1
> > >      maxItems: 3
> > >
> > > +  iommus:
> > > +    maxItems: 1
> > > +
> > > +  qcom,devmem:
> > > +    $ref: /schemas/types.yaml#/definitions/uint32-matrix
> > > +    description:
> > > +      Qualcomm’s PAS implementation for remote processors only supports a
> > > +      single stage of IOMMU translation and is presently managed by the
> > > +      Qualcomm EL2 hypervisor (QHEE) if it is present. In the absence of QHEE,
> > > +      such as with a KVM hypervisor, IOMMU translations need to be set up by
> > > +      the KVM host. Remoteproc might need some device resources and related
> > > +      access permissions to be set before it comes up, and this information is
> > > +      presently available statically with QHEE.
> > > +
> > > +      In the absence of QHEE, the boot firmware needs to overlay this
> > > +      information based on SoCs running with either QHEE or a KVM hypervisor
> > > +      (CPUs booted in EL2).
> > > +
> > > +      The qcom,devmem property provides IOMMU devmem translation information
> > > +      intended for non-QHEE based systems. It is an array of u32 values
> > > +      describing the device memory regions for which IOMMU translations need to
> > > +      be set up before bringing up Remoteproc. This array consists of 4-tuples
> > > +      defining the device address, physical address, size, and attribute flags
> > > +      with which it has to be mapped.
> >
> > I'd expect that this kind of information is hardware-dependent. As such
> > it can go to the driver itself, rather than the device tree. The driver
> > can use compatible string to select the correct table.
> >
>
> IIUC, are you saying that to move this into driver file and override the
> compatible string via overlay ?

Ideally we should live without compat overrides. On the other hand,
sc7180 and sc7280 provide an example of doing exactly that.

>
> > > +
> > > +      remoteproc@...0000 {
> > > +          ...
> > > +
> > > +          qcom,devmem = <0x82000 0x82000 0x2000 0x3>,
> > > +                        <0x92000 0x92000 0x1000 0x1>;
> > > +      }
> > > +
> > > +    items:
> > > +      items:
> > > +        - description: device address
> > > +        - description: physical address
> > > +        - description: size of mapping
> > > +        - description: |
> > > +            iommu attributes - IOMMU_READ, IOMMU_WRITE, IOMMU_CACHE, IOMMU_NOEXEC, IOMMU_MMIO
> > > +          enum: [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
> > > +                  25, 26, 27, 28, 29, 30, 31 ]
> >
> > Attributes should definitely be defined and then the DT should use
> > defines rather than the raw values.
> >
>
> Ack.
>
> -Mukesh
>


-- 
With best wishes
Dmitry