From: Eric Anholt <eric@anholt.net>
To: Archit Taneja <architt@codeaurora.org>,
dri-devel@lists.freedesktop.org,
Andrzej Hajda <a.hajda@samsung.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Thierry Reding <thierry.reding@gmail.com>,
Rob Herring <robh+dt@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge.
Date: Tue, 20 Jun 2017 10:31:03 -0700 [thread overview]
Message-ID: <871sqe7ei0.fsf@eliezer.anholt.net> (raw)
In-Reply-To: <8e148170-b626-b426-3c94-b93d2746f4ce@codeaurora.org>
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Archit Taneja <architt@codeaurora.org> writes:
> On 06/16/2017 08:13 PM, Eric Anholt wrote:
>> Archit Taneja <architt@codeaurora.org> writes:
>>
>>> On 06/16/2017 02:11 AM, Eric Anholt wrote:
>>>> If the panel-bridge is being set up after the drm_mode_config_reset(),
>>>> then the connector's state would never get initialized, and we'd
>>>> dereference the NULL in the hotplug path. We also need to register
>>>> the connector, so that userspace can get at it.
>>>>
>>>
>>> Shouldn't the KMS driver make sure the panel-bridge is set up before
>>> drm_mode_config_reset? Is it the case when we're inserting the
>>> panel-bridge driver as a module?
>>>
>>>
>>> All the connectors that have been added are registered automatically
>>> when drm_dev_register() is called by the KMS driver. Registering a
>>> connector in the middle of setting up our driver is prone to race
>>> conditions if the userspace decides to use them immediately.
>>
>> Yeah, this is fixing initializing panel_bridge at DSI host_attach time,
>> which in the case of a panel module that creates the DSI device
>> (adv7533-style, like you said I should use as a reference) will be after
>> drm_mode_config_reset() and drm_dev_register().
>
> Okay. In the case of the msm kms driver, we defer probe until the
> adv7533 module is inserted, only then we proceed to drm_mode_config_reset()
> and drm_dev_register(). I assumed this was the general practice followed by
> most kms drivers. I.,e the kms driver defers probe until all connector
> related modules are inserted, and only then proceed to create a drm device.
The problem, though, is the panel driver needs the MIPI DSI host to
exist to call mipi_dsi_device_register_full() during the probe process.
The adv7533 driver gets around this by registering the DSI device in the
bridge attach step, but drm_panel doesn't have an attach step.
Another alternative is my original version of the panel driver that was
a mipi_dsi_device driver that registered the panel during the DSI device
probe. That's why vc4's panel lookup is during the MIPI DSI attach
phase, currently.
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next prev parent reply other threads:[~2017-06-20 17:31 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-15 20:41 [PATCH 0/7] RPi touchscreen as a panel driver again Eric Anholt
2017-06-15 20:41 ` [PATCH 1/7] drm/bridge: Support hotplugging panel-bridge Eric Anholt
2017-06-16 5:43 ` Archit Taneja
2017-06-16 14:43 ` Eric Anholt
2017-06-20 3:48 ` Archit Taneja
2017-06-20 7:31 ` Laurent Pinchart
2017-06-20 17:31 ` Eric Anholt [this message]
2017-06-22 7:50 ` Benjamin Gaignard
2017-06-22 8:17 ` Archit Taneja
2017-06-22 9:23 ` Boris Brezillon
2017-06-22 12:29 ` Andrzej Hajda
2017-06-22 12:41 ` Boris Brezillon
2017-06-22 13:16 ` Andrzej Hajda
2017-06-22 13:34 ` Boris Brezillon
2017-06-23 7:22 ` Andrzej Hajda
2017-06-23 7:32 ` Boris Brezillon
2017-06-23 13:54 ` Archit Taneja
2017-06-23 21:50 ` Eric Anholt
2017-06-27 6:53 ` Archit Taneja
2017-06-22 9:31 ` Philippe CORNU
2017-06-23 21:36 ` Eric Anholt
2017-06-23 9:04 ` Daniel Vetter
2017-06-15 20:41 ` [PATCH 2/7] drm/vc4: Fix DSI T_INIT timing Eric Anholt
2017-06-15 20:41 ` [PATCH 3/7] drm/vc4: Fix misleading name of the continuous flag Eric Anholt
2017-06-15 20:41 ` [PATCH 4/7] drm/vc4: Use drm_mode_vrefresh() in DSI fixup, in case vrefresh is 0 Eric Anholt
2017-06-15 20:41 ` [PATCH 5/7] dt-bindings: Document the Raspberry Pi Touchscreen nodes Eric Anholt
2017-06-23 18:44 ` Rob Herring
2017-06-15 20:41 ` [PATCH 6/7] drm/panel: Add support for the Raspberry Pi 7" Touchscreen Eric Anholt
2017-06-15 20:41 ` [PATCH 7/7] ARM: dts: bcm2835: Enable the Raspberry Pi touchscreen panel Eric Anholt
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