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| Started by | Eric Anholt <eric@anholt.net> |
|---|---|
| First post | 2017-07-18 22:20 +0200 |
| Last post | 2017-07-19 05:30 +0200 |
| Articles | 2 — 2 participants |
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Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers. Eric Anholt <eric@anholt.net> - 2017-07-18 22:20 +0200
Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers. Archit Taneja <architt@codeaurora.org> - 2017-07-19 05:30 +0200
| From | Eric Anholt <eric@anholt.net> |
|---|---|
| Date | 2017-07-18 22:20 +0200 |
| Subject | Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers. |
| Message-ID | <u4H8n-6Yu-25@gated-at.bofh.it> |
[Multipart message — attachments visible in raw view] — view raw
Archit Taneja <architt@codeaurora.org> writes:
> 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?
Yeah.
> 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:
I think instead of extending the struct, we can just walk to the parent
similarly to how of_graph_get_remove_port_parent() does. And fix some
node refcounting at the same time:
diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index ed3d505dc203..77d439254da6 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -313,7 +313,12 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
* connect our host to it and probe them now.
*/
list_for_each_entry_safe(dsi, temp, &unattached_device_list, list) {
- if (of_get_parent(dsi->dev.of_node) == host->dev->of_node) {
+ struct device_node *host_node = of_get_parent(dsi->dev.of_node);
+
+ if (!of_node_cmp(host_node->name, "ports"))
+ host_node = of_get_next_parent(host_node);
+
+ if (host_node == host->dev->of_node) {
dsi->host = host;
dsi->dev.parent = host->dev;
device_initialize(&dsi->dev);
@@ -321,6 +326,8 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
mipi_dsi_device_add(dsi);
list_del_init(&dsi->list);
}
+
+ of_node_put(host_node);
}
mutex_unlock(&host_lock);
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| From | Archit Taneja <architt@codeaurora.org> |
|---|---|
| Date | 2017-07-19 05:30 +0200 |
| Subject | Re: [PATCH 6/8] drm: Allow DSI devices to be registered before the host registers. |
| Message-ID | <u4NQt-2L1-9@gated-at.bofh.it> |
| In reply to | #1690632 |
On 07/19/2017 01:43 AM, Eric Anholt wrote:
> Archit Taneja <architt@codeaurora.org> writes:
>
>> 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?
>
> Yeah.
>
>
>> 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:
>
> I think instead of extending the struct, we can just walk to the parent
> similarly to how of_graph_get_remove_port_parent() does. And fix some
> node refcounting at the same time:
Yeah, I guess this works. The only thing that's a slight irritant is that
we're setting an 'of_node' to a device that doesn't have a DT
representation. But I don't have any strong feelings against it.
Reviewed-by: Archit Taneja <architt@codeaurora.org>
>
> diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> index ed3d505dc203..77d439254da6 100644
> --- a/drivers/gpu/drm/drm_mipi_dsi.c
> +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> @@ -313,7 +313,12 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
> * connect our host to it and probe them now.
> */
> list_for_each_entry_safe(dsi, temp, &unattached_device_list, list) {
> - if (of_get_parent(dsi->dev.of_node) == host->dev->of_node) {
> + struct device_node *host_node = of_get_parent(dsi->dev.of_node);
> +
> + if (!of_node_cmp(host_node->name, "ports"))
> + host_node = of_get_next_parent(host_node);
> +
> + if (host_node == host->dev->of_node) {
> dsi->host = host;
> dsi->dev.parent = host->dev;
> device_initialize(&dsi->dev);
> @@ -321,6 +326,8 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
> mipi_dsi_device_add(dsi);
> list_del_init(&dsi->list);
> }
> +
> + of_node_put(host_node);
> }
> mutex_unlock(&host_lock);
>
>
--
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