From: Archit Taneja <architt@codeaurora.org>
To: Eric Anholt <eric@anholt.net>,
dri-devel@lists.freedesktop.org,
Andrzej Hajda <a.hajda@samsung.com>,
Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
Thierry Reding <thierry.reding@gmail.com>
Cc: Boris Brezillon <boris.brezillon@free-electrons.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers.
Date: Mon, 17 Jul 2017 09:56:49 +0530 [thread overview]
Message-ID: <c187aa6c-6817-ca5b-7b1b-450f82fccf93@codeaurora.org> (raw)
In-Reply-To: <87vamu7hi4.fsf@eliezer.anholt.net>
On 07/15/2017 04:28 AM, Eric Anholt wrote:
> Archit Taneja <architt@codeaurora.org> writes:
>
>> On 06/28/2017 01:28 AM, Eric Anholt wrote:
>>> When a mipi_dsi_host is registered, the DT is walked to find any child
>>> nodes with compatible strings. Those get registered as DSI devices,
>>> and most DSI panel drivers are mipi_dsi_drivers that attach to those nodes.
>>>
>>> There is one special case currently, the adv7533 bridge, where the
>>> bridge probes on I2C, and during the bridge attach step it looks up
>>> the mipi_dsi_host and registers the mipi_dsi_device (for its own stub
>>> mipi_dsi_driver).
>>>
>>> For the Raspberry Pi panel, though, we also need to attach on I2C (our
>>> control bus), but don't have a bridge driver. The lack of a bridge's
>>> attach() step like adv7533 uses means that we aren't able to delay the
>>> mipi_dsi_device creation until the mipi_dsi_host is present.
>>>
>>> To fix this, we extend mipi_dsi_device_register_full() to allow being
>>> called with a NULL host, which puts the device on a queue waiting for
>>> a host to appear. When a new host is registered, we fill in the host
>>> value and finish the device creation process.
>>
>> This is quite a nice idea. The only bothering thing is the info.of_node usage
>> varies between child nodes (mipi_dsi_devs) and non-child nodes (i2c control
>> bus).
>>
>> For DSI children expressed in DT, the of_node in info holds the DT node
>> corresponding to the DSI child itself. For non-DT ones, this patch assumes
>> that info.of_node stores the DSI host DT node. I think it should be okay as
>> long as we mention the usage in a comment somewhere. The other option is to
>> have a new info.host_node field to keep a track of the host DT node.
>
> I think maybe you misread the patch? We're using
> of_get_parent(dsi->dev.node), which came from info->node, to compare to
> host->dev->of_node().
I think I did misread it.
Although, I'm not entirely clear what we should be setting info.node to.
In patch #8, info.node is set by:
endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
info.node = of_graph_get_remote_port(endpoint);
Looking at the dt bindings in patch #7, it looks like info.node is set
to the 'port' device node in dsi@7e700000, is that right?
I suppose 'port' here seems like a reasonable representation of
dsi->dev.node, I wonder how it would work if the dsi host had multiple
ports underneath it. I.e:
dsi@7e700000 {
...
...
ports {
port@0 {
...
dsi_out_port: endpoint {
remote-endpoint = <&panel_dsi_port>;
};
};
port@1 {
...
...
};
};
};
Here, we would need to set info.node to the 'ports' node, so that
of_get_parent(dsi->dev.of_node) equals host->dev->of_node. That doesn't
seem correct.
Ideally, a dev's 'of_node' should be left to NULL if we don't have a
corresponding OF node. We're sort of overriding it here since we don't
have any other place to store this information in the mipi_dsi_device
struct.
Maybe we could add a 'host_node' entry in mipi_dsi_device itself, which
is exclusively used cases where the DSI device doesn't have a DT node.
Our check in mipi_dsi_host_register() could then be something like:
if (dsi->host_node) == host->dev->of_node) {
...
...
}
Since Thierry also reviews drm_mipi_dsi.c changes, it would nice to
get some comments from him too.
Thanks,
Archit
--
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project
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next prev parent reply other threads:[~2017-07-17 4:26 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-27 19:58 [PATCH 0/8] RPi touchscreen panel driver v4 Eric Anholt
2017-06-27 19:58 ` [PATCH 1/8] drm/vc4: Fix DSI T_INIT timing Eric Anholt
2017-06-29 9:02 ` Andrzej Hajda
2017-06-27 19:58 ` [PATCH 2/8] drm/vc4: Fix misleading name of the continuous flag Eric Anholt
2017-06-29 9:03 ` Andrzej Hajda
2017-06-27 19:58 ` [PATCH 3/8] drm/vc4: Use drm_mode_vrefresh() in DSI fixup, in case vrefresh is 0 Eric Anholt
2017-06-29 9:24 ` Andrzej Hajda
2017-06-27 19:58 ` [PATCH 4/8] drm/bridge: Add a devm_ allocator for panel bridge Eric Anholt
2017-06-29 9:30 ` Andrzej Hajda
2017-06-27 19:58 ` [PATCH 5/8] drm/vc4: Delay DSI host registration until the panel has probed Eric Anholt
2017-06-29 9:42 ` Andrzej Hajda
2017-06-27 19:58 ` [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers Eric Anholt
2017-06-29 5:03 ` Archit Taneja
2017-06-29 10:39 ` Andrzej Hajda
2017-06-29 15:22 ` Eric Anholt
2017-06-30 8:48 ` Andrzej Hajda
2017-07-03 10:56 ` Archit Taneja
2017-07-14 23:01 ` Eric Anholt
2017-07-17 13:39 ` Archit Taneja
2017-07-14 22:58 ` Eric Anholt
2017-07-17 4:26 ` Archit Taneja [this message]
2017-07-18 20:13 ` Eric Anholt
2017-07-19 3:29 ` Archit Taneja
2017-08-04 9:29 ` Boris Brezillon
2017-06-27 19:58 ` [PATCH 7/8] dt-bindings: Document the Raspberry Pi Touchscreen nodes Eric Anholt
2017-06-27 19:58 ` [PATCH 8/8] drm/panel: Add support for the Raspberry Pi 7" Touchscreen Eric Anholt
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