linux-kernel - Re: [PATCH] drm/msm/dp: Remove INIT

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Message-ID: <e55b52b3-91a7-9dc6-9d3c-1587b50f0fef@quicinc.com>
Date:   Tue, 17 Jan 2023 10:11:44 -0800
From:   Kuogee Hsieh <quic_khsieh@...cinc.com>
To:     Bjorn Andersson <quic_bjorande@...cinc.com>,
        Rob Clark <robdclark@...il.com>,
        Abhinav Kumar <quic_abhinavk@...cinc.com>,
        "Dmitry Baryshkov" <dmitry.baryshkov@...aro.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Johan Hovold <johan+linaro@...nel.org>,
        Sankeerth Billakanti <quic_sbillaka@...cinc.com>
CC:     Sean Paul <sean@...rly.run>, David Airlie <airlied@...il.com>,
        "Daniel Vetter" <daniel@...ll.ch>, <linux-arm-msm@...r.kernel.org>,
        <dri-devel@...ts.freedesktop.org>,
        <freedreno@...ts.freedesktop.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] drm/msm/dp: Remove INIT_SETUP delay


On 1/17/2023 9:29 AM, Bjorn Andersson wrote:
> During initalization of the DisplayPort controller an EV_HPD_INIT_SETUP
> event is generated, but with a delay of 100 units. This delay existed to
> circumvent bug in the QMP combo PHY driver, where if the DP part was
> powered up before USB, the common properties would not be properly
> initialized - and USB wouldn't work.
>
> This issue was resolved in the recent refactoring of the QMP driver,
> so it's now possible to remove this delay.
>
> While there is still a timing dependency in the current implementation,
> test indicates that it's now possible to boot with an external display
> on USB Type-C and have the display power up, without disconnecting and
> reconnecting the cable.
>
> Signed-off-by: Bjorn Andersson <quic_bjorande@...cinc.com>
Reviewed-by: Kuogee Hsieh <quic_khsieh@...cinc.com>
> ---
>   drivers/gpu/drm/msm/dp/dp_display.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/msm/dp/dp_display.c b/drivers/gpu/drm/msm/dp/dp_display.c
> index db9783ffd5cf..bde1a7ce442f 100644
> --- a/drivers/gpu/drm/msm/dp/dp_display.c
> +++ b/drivers/gpu/drm/msm/dp/dp_display.c
> @@ -1506,7 +1506,7 @@ void msm_dp_irq_postinstall(struct msm_dp *dp_display)
>   	dp = container_of(dp_display, struct dp_display_private, dp_display);
>   
>   	if (!dp_display->is_edp)
> -		dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 100);
> +		dp_add_event(dp, EV_HPD_INIT_SETUP, 0, 0);
>   }
>   
>   bool msm_dp_wide_bus_available(const struct msm_dp *dp_display)