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

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Message-ID: <ZwP/tA06k6we7uUh@hu-mojha-hyd.qualcomm.com>
Date: Mon, 7 Oct 2024 21:05:16 +0530
From: Mukesh Ojha <quic_mojha@...cinc.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
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 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 ?

> > +
> > +      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