Re: [v3,3/7] drm/bridge_connector: rely on drm_kms_helper_poll_* for HPD enablement

From: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
To: neil.armstrong@linaro.org,
	Marek Szyprowski <m.szyprowski@samsung.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, Daniel Vetter <daniel@ffwll.ch>,
	Laurentiu Palcu <laurentiu.palcu@oss.nxp.com>,
	Lucas Stach <l.stach@pengutronix.de>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Pengutronix Kernel Team <kernel@pengutronix.de>,
	Fabio Estevam <festevam@gmail.com>,
	NXP Linux Team <linux-imx@nxp.com>,
	Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
	Abhinav Kumar <quic_abhinavk@quicinc.com>,
	Tomi Valkeinen <tomba@kernel.org>
Cc: linux-arm-msm@vger.kernel.org, freedreno@lists.freedesktop.org,
	linux-arm-kernel@lists.infradead.org,
	dri-devel@lists.freedesktop.org,
	linux-amlogic@lists.infradead.org
Subject: Re: [v3,3/7] drm/bridge_connector: rely on drm_kms_helper_poll_* for HPD enablement
Date: Thu, 12 Jan 2023 11:36:11 +0200	[thread overview]
Message-ID: <a11d3c82-1be5-2185-4ff1-48dd54ce9a55@linaro.org> (raw)
In-Reply-To: <c7a6714c-edcc-fa1c-ff83-2e066c7bbd84@linaro.org>

On 12/01/2023 11:35, Neil Armstrong wrote:
> On 11/01/2023 13:41, Marek Szyprowski wrote:
>> On 02.11.2022 19:07, Dmitry Baryshkov wrote:
>>> Use drm_connector's helpers enable_hpd and disable_hpd to enable and
>>> disable HPD automatically by the means of drm_kms_helper_poll_*
>>> functions. As the drm_bridge_connector_enable_hpd() and
>>> drm_bridge_connector_disable_hpd() functions are now unused, replace
>>> them with stubs to ease driver migration.
>>>
>>> Enabling the HPD from drm_bridge_connector_init() can happen too early,
>>> before the driver is prepared to handle HPD events. As the
>>> drm_bridge_connector_enable_hpd() is empty anyway, drop this call
>>> anyway.
>>>
>>> Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
>>> ---
>>
>> This patch, merged to recent linux-next as commit 92d755d8f13b
>> ("drm/bridge_connector: rely on drm_kms_helper_poll_* for HPD
>> enablement"), triggers the following warning on all my Amlogic Meson
>> based boards:
>>
>> ------------[ cut here ]------------
>> Hot plug detection already enabled
>> WARNING: CPU: 2 PID: 285 at drivers/gpu/drm/drm_bridge.c:1257
>> drm_bridge_hpd_enable+0x90/0xa0
>> Modules linked in: snd_soc_meson_axg_frddr snd_soc_meson_axg_fifo
>> dwmac_generic panfrost(+) reset_meson_audio_arb(+) drm_shmem_helper
>> meson_dw_hdmi(+) dw_hdmi rc_odroid drm_display_helper meson_ir(+)
>> gpu_sched meson_rng rng_core meson_gxbb_wdt crct10dif_ce dwmac_meson8b
>> stmmac_platform snd_soc_meson_axg_sound_card snd_soc_meson_card_utils
>> mdio_mux_meson_g12a stmmac meson_drm pwm_meson pcs_xpcs meson_canvas
>> snd_soc_meson_axg_tdm_interface rtc_meson_vrtc
>> snd_soc_meson_axg_tdm_formatter nvmem_meson_efuse display_connector
>> CPU: 2 PID: 285 Comm: systemd-udevd Not tainted 6.1.0-rc6+ #13236
>> Hardware name: Hardkernel ODROID-C4 (DT)
>> pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
>> pc : drm_bridge_hpd_enable+0x90/0xa0
>> lr : drm_bridge_hpd_enable+0x90/0xa0
>> ...
>> Call trace:
>>    drm_bridge_hpd_enable+0x90/0xa0
>>    _drm_bridge_connector_enable_hpd+0x24/0x34
> 
> Weird because _drm_bridge_connector_enable_hpd() has been removed with
> 4c00ac500d0e ("drm/bridge_connector: drop 
> drm_bridge_connector_en/disable_hpd()")
> 
> 
>>    drm_kms_helper_poll_enable.part.0+0x50/0xd0
> 
> It seems drm_kms_helper_poll_enable is called again by
> drm_helper_probe_single_connector_modes() because poll_running isn't set.

Yes, I'm currently reworking poll_running handling. I hope to post a 
patch today.

-- 
With best wishes
Dmitry

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