Re: [PATCH v1] drm/msm/dp: use dp_hpd_plug_handle() and dp_hpd_unplug_handle() directly

From: Abhinav Kumar <quic_abhinavk@quicinc.com>
To: Stephen Boyd <swboyd@chromium.org>,
	Bjorn Andersson <andersson@kernel.org>,
	Johan Hovold <johan@kernel.org>,
	Kuogee Hsieh <quic_khsieh@quicinc.com>, <abel.vesa@linaro.org>,
	<agross@kernel.org>, <airlied@gmail.com>, <daniel@ffwll.ch>,
	<dianders@chromium.org>, <dmitry.baryshkov@linaro.org>,
	<dri-devel@lists.freedesktop.org>, <robdclark@gmail.com>,
	<sean@poorly.run>, <vkoul@kernel.org>
Cc: <quic_jesszhan@quicinc.com>, <quic_sbillaka@quicinc.com>,
	<marijn.suijten@somainline.org>,
	<freedreno@lists.freedesktop.org>,
	<linux-arm-msm@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v1] drm/msm/dp: use dp_hpd_plug_handle() and dp_hpd_unplug_handle() directly
Date: Thu, 28 Mar 2024 14:21:14 -0700	[thread overview]
Message-ID: <23de89e9-3ef3-c52d-7abf-93dc2dbb51a4@quicinc.com> (raw)
In-Reply-To: <CAE-0n503FwcwreZ14MMKgdzu8QybWYtMdLOKasiCwmE8pCJOSw@mail.gmail.com>

On 3/28/2024 1:58 PM, Stephen Boyd wrote:
> Quoting Abhinav Kumar (2024-03-28 13:24:34)
>> + Johan and Bjorn for FYI
>>
>> On 3/28/2024 1:04 PM, Kuogee Hsieh wrote:
>>> For internal HPD case, hpd_event_thread is created to handle HPD
>>> interrupts generated by HPD block of DP controller. It converts
>>> HPD interrupts into events and executed them under hpd_event_thread
>>> context. For external HPD case, HPD events is delivered by way of
>>> dp_bridge_hpd_notify() under thread context. Since they are executed
>>> under thread context already, there is no reason to hand over those
>>> events to hpd_event_thread. Hence dp_hpd_plug_handle() and
>>> dp_hpd_unplug_hanlde() are called directly at dp_bridge_hpd_notify().
>>>
>>> Signed-off-by: Kuogee Hsieh <quic_khsieh@quicinc.com>
>>> ---
>>>    drivers/gpu/drm/msm/dp/dp_display.c | 5 +++--
>>>    1 file changed, 3 insertions(+), 2 deletions(-)
>>>
>>
>> Fixes: 542b37efc20e ("drm/msm/dp: Implement hpd_notify()")
> 
> Is this a bug fix or an optimization? The commit text doesn't tell me.
> 

I would say both.

optimization as it avoids the need to go through the hpd_event thread 
processing.

bug fix because once you go through the hpd event thread processing it 
exposes and often breaks the already fragile hpd handling state machine 
which can be avoided in this case.

>>
>> Looks right to me,
>>
>> Reviewed-by: Abhinav Kumar <quic_abhinavk@quicinc.com>