linux-kernel - Re: [PATCH 5/6] phy: qcom-qmp-combo: fix drm bridge registration

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Message-ID: <CAA8EJppnHY=jDYjgTn+2dF_zmGwM9+KsUS6vOyPB_wa9W0v-UA@mail.gmail.com>
Date: Thu, 22 Feb 2024 23:11:17 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Johan Hovold <johan+linaro@...nel.org>
Cc: Bjorn Andersson <andersson@...nel.org>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Vinod Koul <vkoul@...nel.org>, Jonas Karlman <jonas@...boo.se>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Kuogee Hsieh <quic_khsieh@...cinc.com>, 
	freedreno@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	linux-phy@...ts.infradead.org, stable@...r.kernel.org, 
	Bjorn Andersson <quic_bjorande@...cinc.com>
Subject: Re: [PATCH 5/6] phy: qcom-qmp-combo: fix drm bridge registration

On Sat, 17 Feb 2024 at 17:03, Johan Hovold <johan+linaro@...nel.org> wrote:
>
> Due to a long-standing issue in driver core, drivers may not probe defer
> after having registered child devices to avoid triggering a probe
> deferral loop (see fbc35b45f9f6 ("Add documentation on meaning of
> -EPROBE_DEFER")).
>
> This could potentially also trigger a bug in the DRM bridge
> implementation which does not expect bridges to go away even if device
> links may avoid triggering this (when enabled).
>
> Move registration of the DRM aux bridge to after looking up clocks and
> other resources.
>
> Note that PHY creation can in theory also trigger a probe deferral when
> a 'phy' supply is used. This does not seem to affect the QMP PHY driver
> but the PHY subsystem should be reworked to address this (i.e. by
> separating initialisation and registration of the PHY).
>
> Fixes: 35921910bbd0 ("phy: qcom: qmp-combo: switch to DRM_AUX_BRIDGE")
> Fixes: 1904c3f578dc ("phy: qcom-qmp-combo: Introduce drm_bridge")
> Cc: stable@...r.kernel.org      # 6.5
> Cc: Bjorn Andersson <quic_bjorande@...cinc.com>
> Cc: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
> Signed-off-by: Johan Hovold <johan+linaro@...nel.org>
> ---
>  drivers/phy/qualcomm/phy-qcom-qmp-combo.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>


-- 
With best wishes
Dmitry