linux-kernel - Re: [PATCH v2 0/4] soc: qcom: Introduce PMIC GLINK

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Message-ID: <20230117025818.GC2350793@hu-bjorande-lv.qualcomm.com>
Date:   Mon, 16 Jan 2023 18:58:18 -0800
From:   Bjorn Andersson <quic_bjorande@...cinc.com>
To:     Bryan O'Donoghue <bryan.odonoghue@...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>,
        Sebastian Reichel <sre@...nel.org>,
        <linux-arm-msm@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <linux-pm@...r.kernel.org>,
        Subbaraman Narayanamurthy <quic_subbaram@...cinc.com>,
        Johan Hovold <johan@...nel.org>,
        Neil Armstrong <neil.armstrong@...aro.org>
Subject: Re: [PATCH v2 0/4] soc: qcom: Introduce PMIC GLINK

On Tue, Jan 17, 2023 at 02:37:27AM +0000, Bryan O'Donoghue wrote:
> On 17/01/2023 02:32, Bjorn Andersson wrote:
> > On Fri, Jan 13, 2023 at 05:10:17PM +0000, Bryan O'Donoghue wrote:
> > > On 13/01/2023 04:11, Bjorn Andersson wrote:
> > > > This implements the base PMIC GLINK driver, a power_supply driver and a
> > > > driver for the USB Type-C altmode protocol. This has been tested and
> > > > shown to provide battery information, USB Type-C switch and mux requests
> > > > and DisplayPort notifications on SC8180X, SC8280XP and SM8350.
> > > > 
> > > > Bjorn Andersson (4):
> > > >     dt-bindings: soc: qcom: Introduce PMIC GLINK binding
> > > >     soc: qcom: pmic_glink: Introduce base PMIC GLINK driver
> > > >     soc: qcom: pmic_glink: Introduce altmode support
> > > >     power: supply: Introduce Qualcomm PMIC GLINK power supply
> > > > 
> > > >    .../bindings/soc/qcom/qcom,pmic-glink.yaml    |  102 ++
> > > >    drivers/power/supply/Kconfig                  |    9 +
> > > >    drivers/power/supply/Makefile                 |    1 +
> > > >    drivers/power/supply/qcom_battmgr.c           | 1421 +++++++++++++++++
> > > >    drivers/soc/qcom/Kconfig                      |   15 +
> > > >    drivers/soc/qcom/Makefile                     |    2 +
> > > >    drivers/soc/qcom/pmic_glink.c                 |  336 ++++
> > > >    drivers/soc/qcom/pmic_glink_altmode.c         |  477 ++++++
> > > >    include/linux/soc/qcom/pmic_glink.h           |   32 +
> > > >    9 files changed, 2395 insertions(+)
> > > >    create mode 100644 Documentation/devicetree/bindings/soc/qcom/qcom,pmic-glink.yaml
> > > >    create mode 100644 drivers/power/supply/qcom_battmgr.c
> > > >    create mode 100644 drivers/soc/qcom/pmic_glink.c
> > > >    create mode 100644 drivers/soc/qcom/pmic_glink_altmode.c
> > > >    create mode 100644 include/linux/soc/qcom/pmic_glink.h
> > > > 
> > > 
> > > How does the USB PHY and a USB redriver fit into this ?
> > > 
> > > Is the host supposed to manage both/neither ? Is the DSP responsible for
> > > configuring the PHY lanes and the turnaround on orientation switch ?
> > > 
> > 
> > As indicated above, the firmware deals with battery management and USB
> > Type-C handling.
> > 
> > The battery/power management is handled by the battmgr implementation,
> > exposing the various properties through a set of power_supply objects.
> > 
> > The USB Type-C handling comes in two forms. The "altmode" protocol
> > handles DisplayPort notifications - plug detect, orientation and mode
> > switches. The other part of the USB implementation exposes UCSI.
> > 
> > The altmode implementation provides two things:
> > - A drm_bridge, per connector, which can be tied (of_graph) to a
> >    DisplayPort instance, and will invoke HPD notifications on the
> >    drm_bridge, based on notification messages thereof.
> > 
> > - Acquire typec_switch and typec_mux handles through the of_graph and
> >    signal the remotes when notifications of state changes occur. Linking
> >    this to the FSA4480, is sufficient to get USB/DP combo (2+2 lanes)
> >    working on e.g. SM8350 HDK.
> >    Work in progress patches also exists for teaching QMP about
> >    orientation switching of the SS lines, but it seems this needs to be
> >    rebased onto the refactored QMP driver.
> >    I also have patches for QMP to make it switch USB/DP combo -> 4-lane
> >    DP, which allow 4k support without DSC, unfortunately switch back to
> >    USB has not been fully reliable, so this requires some more work
> >    (downstream involves DWC3 here as well, to reprogram the PHY).
> 
> Oki doki that makes sense and is pretty much in-line with what I thought.
> 
> We still have a bunch of typec-mux and phy work to do even with adsp/glink
> doing the TCPM.
> 

Correct, the registration of QMP as a typec_switch and typec_mux and
handling of respective notification remains open and should (by design)
be independent of the TCPM implementation.

In particular the orientation switching is an itch worth scratching at
this time. But when the DPU becomes capable of producing 4k@60 output it
would obviously be nice to have the whole shebang :)

Regards,
Bjorn

> Thanks for the explanation.
> 
> ---
> bod
>