Re: [PATCH v2 6/8] drm/dsi: add helper function to find the second host in a dual-dsi setup

Heiko Stuebner
2018-07-04T10:47:29Z

Am Dienstag, 3. Juli 2018, 17:06:48 CEST schrieb Andrzej Hajda:
> On 18.06.2018 12:28, Heiko Stuebner wrote:
> > >From a specified output port of one dsi controller this function allows to
> > iterate over the list of registered dsi controllers trying to find a second
> > instance connected to the same display, like it is used in dual-dsi setups.
> >
> > Signed-off-by: Heiko Stuebner <heiko@sntech.de>
>
> The code looks hacky to me - it iterates over external nodes, it assumes
> all graph links are dedicated exclusively to dsi

The loop iterates over all registered dsi controllers and checks the same
port/endpoint combination as on the primary host.

One assumption is that the dsi controllers are identical, but that is
also an argument

As the splitting of the output to two DSI-controllers is a special
feature of the socs CRTC, I'd think the chances are very slim that
there will be two completely different DSI controllers used for
something like this.

> it assumes that there
> is no additional node between dsi host and the panel.

Yep.

Heiko

> > ---
> > drivers/gpu/drm/drm_mipi_dsi.c | 56 ++++++++++++++++++++++++++++++++++
> > include/drm/drm_mipi_dsi.h | 2 ++
> > 2 files changed, 58 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
> > index bc73b7f5b9fc..0c3c9c7aa3b8 100644
> > --- a/drivers/gpu/drm/drm_mipi_dsi.c
> > +++ b/drivers/gpu/drm/drm_mipi_dsi.c
> > @@ -30,6 +30,7 @@
> > #include <linux/device.h>
> > #include <linux/module.h>
> > #include <linux/of_device.h>
> > +#include <linux/of_graph.h>
> > #include <linux/pm_runtime.h>
> > #include <linux/slab.h>
> >
> > @@ -282,6 +283,61 @@ struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node)
> > }
> > EXPORT_SYMBOL(of_find_mipi_dsi_host_by_node);
> >
> > +struct device_node *of_mipi_dsi_find_second_host(struct device_node *first_np,
> > + int port, int endpoint)
> > +{
> > + struct mipi_dsi_host *first, *host;
> > + struct device_node *remote, *np, *second_np = NULL;
> > + int num = 0;
> > +
> > + first = of_find_mipi_dsi_host_by_node(first_np);
> > + if (!first) {
> > + pr_err("no dsi-host for node %s\n", first_np->full_name);
> > + return ERR_PTR(-ENODEV);
> > + }
> > +
> > + /* output-node of the known dsi-host */
> > + remote = of_graph_get_remote_node(first_np, port, endpoint);
> > + if (!remote) {
> > + dev_err(first->dev, "no output node found\n");
> > + return ERR_PTR(-ENODEV);
> > + }
> > +
> > + mutex_lock(&host_lock);
> > +
> > + list_for_each_entry(host, &host_list, list) {
> > + np = of_graph_get_remote_node(host->dev->of_node,
> > + port, endpoint);
> > +
> > + /* found a host connected to this panel */
> > + if (np == remote)
> > + num++;
> > +
> > + /* found one second host */
> > + if (host->dev->of_node != first_np)
> > + second_np = host->dev->of_node;
> > +
> > + of_node_put(np);
> > + }
> > +
> > + /* of_node_get the node under host_lock */
> > + if (num == 2)
> > + of_node_get(second_np);
> > +
> > + mutex_unlock(&host_lock);
> > +
> > + of_node_put(remote);
> > +
> > + if (num > 2) {
> > + dev_err(first->dev,
> > + "too many DSI links for output: %d links\n", num);
> > + return ERR_PTR(-EINVAL);
> > + }
> > +
> > + return second_np;
> > +}
> > +EXPORT_SYMBOL(of_mipi_dsi_find_second_host);
> > +
> > int mipi_dsi_host_register(struct mipi_dsi_host *host)
> > {
> > struct device_node *node;
> > diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
> > index 4fef19064b0f..89532ae69c91 100644
> > --- a/include/drm/drm_mipi_dsi.h
> > +++ b/include/drm/drm_mipi_dsi.h
> > @@ -107,6 +107,8 @@ struct mipi_dsi_host {
> > int mipi_dsi_host_register(struct mipi_dsi_host *host);
> > void mipi_dsi_host_unregister(struct mipi_dsi_host *host);
> > struct mipi_dsi_host *of_find_mipi_dsi_host_by_node(struct device_node *node);
> > +struct device_node *of_mipi_dsi_find_second_host(struct device_node *first_np,
> > + int port, int endpoint);
> >
> > /* DSI mode flags */
> >