Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <1648656179-10347-1-git-send-email-quic_sbillaka@quicinc.com>
 <1648656179-10347-2-git-send-email-quic_sbillaka@quicinc.com>
 <CAD=FV=X+QvjwoT2zGP82KW4kD0oMUY6ZgCizSikNX_Uj8dNDqA@mail.gmail.com>
 <392b933f-760c-3c81-1040-c514045df3da@linaro.org> <CAD=FV=W4PYK-t607yjRbfjDjjEZX0KdgHDRukw_vSH8E8EDH6w@mail.gmail.com>
 <CAA8EJppt9XONbgtKfmHmN+==QNqiVJeb8GKJFdZm=yyY-tgmHQ@mail.gmail.com>
 <CAD=FV=U5-sTDLYdkeJWLAOG-0wgxR49VxtwUyUO7z2PuibLGsg@mail.gmail.com>
 <CAA8EJppgfYgQjG8A4LsR-1wmBj3Ku3eO8cKfAYhxjWXL7e3eHg@mail.gmail.com>
 <CAD=FV=V=a1CnT8fqTJR40WoS3BaDQ3xZ=HnHVHqZh=MEmVUZBA@mail.gmail.com>
 <3e5fa57f-d636-879a-b98f-77323d07c156@linaro.org> <CAD=FV=Uibu-kZyix7K4_WVc-+C8xpzTqU4WFy7O=6sukMZrX5g@mail.gmail.com>
 <MW4PR02MB7186245772DAC3E04FA8D1C0E1E69@MW4PR02MB7186.namprd02.prod.outlook.com>
 <CAD=FV=Wk3U7_bVdiCPp8iQ4bcCA_Botemu4pwHeRtgBa3Xk6KQ@mail.gmail.com>
 <c4f086ce-c56f-f7c9-4092-7f2432330d50@quicinc.com> <CAD=FV=UmU_BVUaL_X75yOEvQPtGUBTR5-jiVWBHq7uSRt6HM4Q@mail.gmail.com>
 <225d2c0a-42ec-28ad-688c-e7e9e2035ee1@quicinc.com> <CAD=FV=W=WjSACHvRDFBnkLUp-LU2c4XMu3=FTzTx=zexNF5PAw@mail.gmail.com>
 <CAA8EJpqLZ9up4euGEbhf5QyBqm4tJuLcHi7D+0Si7ak9Jej52w@mail.gmail.com> <CAD=FV=XwOzsRf7RnvyBjr5TtedMhC0LJFKoK9tp-kw1eEyuJmQ@mail.gmail.com>
In-Reply-To: <CAD=FV=XwOzsRf7RnvyBjr5TtedMhC0LJFKoK9tp-kw1eEyuJmQ@mail.gmail.com>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Date:   Fri, 8 Apr 2022 15:19:59 +0300
Message-ID: <CAA8EJprb5UF24WRNvGaY_hSqW--NPd=9=8AaPYWSMbUumNn+dQ@mail.gmail.com>
Subject: Re: [PATCH v6 1/8] drm/msm/dp: Add eDP support via aux_bus
To:     Doug Anderson <dianders@chromium.org>
Cc:     Abhinav Kumar <quic_abhinavk@quicinc.com>,
        "Sankeerth Billakanti (QUIC)" <quic_sbillaka@quicinc.com>,
        quic_kalyant <quic_kalyant@quicinc.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        quic_vproddut <quic_vproddut@quicinc.com>,
        David Airlie <airlied@linux.ie>,
        linux-arm-msm <linux-arm-msm@vger.kernel.org>,
        "Kuogee Hsieh (QUIC)" <quic_khsieh@quicinc.com>,
        freedreno <freedreno@lists.freedesktop.org>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        "bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
        Sean Paul <seanpaul@chromium.org>,
        "Aravind Venkateswaran (QUIC)" <quic_aravindh@quicinc.com>,
        Stephen Boyd <swboyd@chromium.org>,
        Sean Paul <sean@poorly.run>,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Fri, 8 Apr 2022 at 03:26, Doug Anderson <dianders@chromium.org> wrote:
>
> Hi,
>
> On Thu, Apr 7, 2022 at 4:46 PM Dmitry Baryshkov
> <dmitry.baryshkov@linaro.org> wrote:
> >
> > > The way I'm arguing it should work is that:
> > >
> > > 1. A whole bunch of the DP init code should move to the DP driver's
> > > probe function. This includes parsing the DT, acquiring clocks,
> > > getting a handle to our PHY, and IO mapping registers. As far as I
> > > know, there's no reason to wait on all the components being probed in
> > > order to do this stuff.
> >
> > Yes. And that's one of the reasons I tried to stay away from the DP
> > driver. Each time I open the source code, my hands itch to start
> > refactoring the code.
> >
> > >
> > > 2. Once we have done the above things, it should be possible to do AUX
> > > transfers, correct? ...and then we can populate the AUX bus from the
> > > probe function too.
> >
> > No. In the DP case the AUX bus is inaccessible until the dongle is
> > plugged (see all the HPD handling, phy_init()/phy_power_on() is hidden
> > somewhere in that path)
>
> I guess my thought was that in DP you could still create the AUX bus
> at probe time. Then for DP you just return an instant "transfer
> failed" from the AUX bus if HPD isn't asserted. For eDP (as discussed
> elsewhere) when we try to do an AUX transfer then we delay until HPD
> is there.

I think panel-edp would already handle the delay, so we do not need to
have this logic in the DP driver.

> So we can still acquire resources (clocks, PHY, io maps, etc) at probe
> time for DP and create the AUX bus, right? It will just return
> "-ENODEV" if HPD isn't asserted and you're DP?

Yes, please. I still suppose that we'd need a separate case to
power_on eDP's PHY during the probe time. Maybe I'm mistaken here.

-- 
With best wishes
Dmitry