linux-kernel - Re: [PATCH 00/11] arm64: qcom: add and enable SHM Bridge support

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Message-ID: <CACMJSet-1tbTnMOab2GvMEc-b6Y3Xq5AZEE4mrfiUOZ=65z3MQ@mail.gmail.com>
Date:   Tue, 29 Aug 2023 21:03:42 +0200
From:   Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Alex Elder <elder@...aro.org>,
        Srini Kandagatla <srinivas.kandagatla@...aro.org>,
        kernel@...cinc.com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 00/11] arm64: qcom: add and enable SHM Bridge support

On Mon, 28 Aug 2023 at 23:24, Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On Mon, 28 Aug 2023 at 22:29, Bartosz Golaszewski
> <bartosz.golaszewski@...aro.org> wrote:
> >
> > SHM Bridge is a mechanism allowing to map limited areas of kernel's
> > virtual memory to physical addresses and share those with the
> > trustzone in order to not expose the entire RAM for SMC calls.
> >
> > This series adds support for Qualcomm SHM Bridge in form of a platform
> > driver and library functions available to users. It enables SHM Bridge
> > support for three platforms and contains a bunch of cleanups for
> > qcom-scm.
>
> Which users do you expect for this API?
>

This series adds a single user: the SCM driver. We have another user
almost ready for upstream in the form of the scminvoke driver and I
learned today, I can already convert another user upstream right now
that I will try to get ready for v2.

> Also, could you please describe your design a bit more? Why have you
> implemented the shm-bridge as a separate driver rather than a part of
> the SCM driver?
>

It's self-contained enough to be put into a separate module and not
all platforms support it so in order to avoid unnecessary ifdeffery in
the scm driver, I made it separate.

Bart

> >
> > Bartosz Golaszewski (11):
> >   firmware: qcom-scm: drop unneeded 'extern' specifiers
> >   firmware: qcom-scm: order includes alphabetically
> >   firmware: qcom-scm: atomically assign and read the global __scm
> >     pointer
> >   firmware: qcom-scm: add support for SHM bridge operations
> >   dt-bindings: document the Qualcomm TEE Shared Memory Bridge
> >   firmware: qcom-shm-bridge: new driver
> >   firmware: qcom-scm: use SHM bridge if available
> >   arm64: defconfig: enable Qualcomm SHM bridge module
> >   arm64: dts: qcom: sm8450: enable SHM bridge
> >   arm64: dts: qcom: sa8775p: enable SHM bridge
> >   arm64: dts: qcom: sm8150: enable SHM bridge
> >
> >  .../bindings/firmware/qcom,shm-bridge.yaml    |  36 ++
> >  arch/arm64/boot/dts/qcom/sa8775p.dtsi         |   4 +
> >  arch/arm64/boot/dts/qcom/sm8150.dtsi          |   4 +
> >  arch/arm64/boot/dts/qcom/sm8450.dtsi          |   4 +
> >  arch/arm64/configs/defconfig                  |   1 +
> >  drivers/firmware/Kconfig                      |   8 +
> >  drivers/firmware/Makefile                     |   1 +
> >  drivers/firmware/qcom-shm-bridge.c            | 452 ++++++++++++++++++
> >  drivers/firmware/qcom_scm-smc.c               |  20 +-
> >  drivers/firmware/qcom_scm.c                   | 106 +++-
> >  drivers/firmware/qcom_scm.h                   |   3 +
> >  include/linux/firmware/qcom/qcom_scm.h        | 109 +++--
> >  include/linux/firmware/qcom/shm-bridge.h      |  32 ++
> >  13 files changed, 712 insertions(+), 68 deletions(-)
> >  create mode 100644 Documentation/devicetree/bindings/firmware/qcom,shm-bridge.yaml
> >  create mode 100644 drivers/firmware/qcom-shm-bridge.c
> >  create mode 100644 include/linux/firmware/qcom/shm-bridge.h
> >
> > --
> > 2.39.2
> >
>
>
> --
> With best wishes
> Dmitry