Re: [PATCH v6 6/8] drm/msm/dp: remove unnecessary delay during boot

From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: "Sankeerth Billakanti (QUIC)" <quic_sbillaka@quicinc.com>
Cc: quic_kalyant <quic_kalyant@quicinc.com>,
	"open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS"
	<devicetree@vger.kernel.org>,
	"bjorn.andersson@linaro.org" <bjorn.andersson@linaro.org>,
	"Abhinav Kumar \(QUIC\)" <quic_abhinavk@quicinc.com>,
	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>,
	Doug Anderson <dianders@chromium.org>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	LKML <linux-kernel@vger.kernel.org>, Sean Paul <sean@poorly.run>,
	Sean Paul <seanpaul@chromium.org>,
	"Aravind Venkateswaran \(QUIC\)" <quic_aravindh@quicinc.com>,
	Stephen Boyd <swboyd@chromium.org>,
	freedreno <freedreno@lists.freedesktop.org>
Subject: Re: [PATCH v6 6/8] drm/msm/dp: remove unnecessary delay during boot
Date: Tue, 5 Apr 2022 00:13:03 +0300	[thread overview]
Message-ID: <CAA8EJpqOzn4xh1N9GhEbH6YY5uHPdeqhiDnSNMM+ZQ3GdaWFrA@mail.gmail.com> (raw)
In-Reply-To: <MW4PR02MB718631182DC72076DC794C1DE1E59@MW4PR02MB7186.namprd02.prod.outlook.com>

On Mon, 4 Apr 2022 at 16:53, Sankeerth Billakanti (QUIC)
<quic_sbillaka@quicinc.com> wrote:
>
> Hi Doug,
>
> > On Wed, Mar 30, 2022 at 9:04 AM Sankeerth Billakanti
> > <quic_sbillaka@quicinc.com> wrote:
> > >
> > > Remove the unnecessary delay in executing the EV_HPD_INIT_SETUP
> > event.
> >
> > Tell me more and put it in the commit message! Why did it used to be
> > necessary and why is it no longer necessary? Inquiring minds want to know.
> >
>
> Okay. I will add proper description. The DP phy is shared with usb and executing the
> dp phy_init before the usb phy_init was causing usb devices to not function.

I always wondered, how does this work for the 4-lane DP dongles, where
there is no USB mode/lanes?

> Earlier, enabling phy_init was done when the EV_HPD_INIT_SETUP event was executed.
> So, we had scheduled it to execute after 10 second to let the usb driver complete the phy_init first.
>
> Kuogee made the below change to move the DP phy_init to execute after the DP is connected
> https://patchwork.kernel.org/project/linux-arm-msm/patch/1642531648-8448-2-git-send-email-quic_khsieh@quicinc.com/
>
> So, there is no need for the DP driver to wait 10 seconds for the phy initialization anymore.
>
> eDP PHY is not shared with usb. So, it can be programmed anytime, hence not needing any delay.

-- 
With best wishes
Dmitry