Commit 10e619f1 authored by Douglas Anderson's avatar Douglas Anderson

drm/bridge: parade-ps8640: Handle DP AUX more properly

While it works, for the most part, to assume that the panel has
finished probing when devm_of_dp_aux_populate_ep_devices() returns,
it's a bit fragile. This is talked about at length in commit
a1e3667a ("drm/bridge: ti-sn65dsi86: Promote the AUX channel to
its own sub-dev").

When reviewing the ps8640 code, I managed to convince myself that it
was OK not to worry about it there and that maybe it wasn't really
_that_ fragile. However, it turns out that it really is. Simply
hardcoding panel_edp_probe() to return -EPROBE_DEFER was enough to put
the boot process into an infinite loop. I believe this manages to trip
the same issues that we used to trip with the main MSM code where
something about our actions trigger Linux to re-probe previously
deferred devices right away and each time we try again we re-trigger
Linux to re-probe.

Let's fix this using the callback introduced in the patch ("drm/dp:
Callbacks to make it easier for drivers to use DP AUX bus properly").
When using the new callback, we have to be a little careful. The
probe_done() callback is no longer always called in the context of
our probe routine. That means we can't rely on being able to return
-EPROBE_DEFER from it. We re-jigger the order of things a bit to
account for that.

With this change, the device still boots (though obviously the panel
doesn't come up) if I force panel-edp to always return
-EPROBE_DEFER. If I fake it and make the panel probe exactly once it
also works.
Signed-off-by: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarDmitry Baryshkov <dmitry.baryshkov@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220510122726.v3.4.Ia6324ebc848cd40b4dbd3ad3289a7ffb5c197779@changeid
parent 50e156bd
......@@ -537,7 +537,7 @@ static const struct drm_bridge_funcs ps8640_bridge_funcs = {
.pre_enable = ps8640_pre_enable,
};
static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridge)
static int ps8640_bridge_get_dsi_resources(struct device *dev, struct ps8640 *ps_bridge)
{
struct device_node *in_ep, *dsi_node;
struct mipi_dsi_device *dsi;
......@@ -576,13 +576,40 @@ static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridg
dsi->format = MIPI_DSI_FMT_RGB888;
dsi->lanes = NUM_MIPI_LANES;
return devm_mipi_dsi_attach(dev, dsi);
return 0;
}
static int ps8640_bridge_link_panel(struct drm_dp_aux *aux)
{
struct ps8640 *ps_bridge = aux_to_ps8640(aux);
struct device *dev = aux->dev;
struct device_node *np = dev->of_node;
int ret;
/*
* NOTE about returning -EPROBE_DEFER from this function: if we
* return an error (most relevant to -EPROBE_DEFER) it will only
* be passed out to ps8640_probe() if it called this directly (AKA the
* panel isn't under the "aux-bus" node). That should be fine because
* if the panel is under "aux-bus" it's guaranteed to have probed by
* the time this function has been called.
*/
/* port@1 is ps8640 output port */
ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0);
if (IS_ERR(ps_bridge->panel_bridge))
return PTR_ERR(ps_bridge->panel_bridge);
ret = devm_drm_bridge_add(dev, &ps_bridge->bridge);
if (ret)
return ret;
return devm_mipi_dsi_attach(dev, ps_bridge->dsi);
}
static int ps8640_probe(struct i2c_client *client)
{
struct device *dev = &client->dev;
struct device_node *np = dev->of_node;
struct ps8640 *ps_bridge;
int ret;
u32 i;
......@@ -623,6 +650,14 @@ static int ps8640_probe(struct i2c_client *client)
if (!ps8640_of_panel_on_aux_bus(&client->dev))
ps_bridge->bridge.ops = DRM_BRIDGE_OP_EDID;
/*
* Get MIPI DSI resources early. These can return -EPROBE_DEFER so
* we want to get them out of the way sooner.
*/
ret = ps8640_bridge_get_dsi_resources(&client->dev, ps_bridge);
if (ret)
return ret;
ps_bridge->page[PAGE0_DP_CNTL] = client;
ps_bridge->regmap[PAGE0_DP_CNTL] = devm_regmap_init_i2c(client, ps8640_regmap_config);
......@@ -665,35 +700,19 @@ static int ps8640_probe(struct i2c_client *client)
if (ret)
return ret;
devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux);
ret = devm_of_dp_aux_populate_bus(&ps_bridge->aux, ps8640_bridge_link_panel);
/* port@1 is ps8640 output port */
ps_bridge->panel_bridge = devm_drm_of_get_bridge(dev, np, 1, 0);
if (IS_ERR(ps_bridge->panel_bridge))
return PTR_ERR(ps_bridge->panel_bridge);
drm_bridge_add(&ps_bridge->bridge);
ret = ps8640_bridge_host_attach(dev, ps_bridge);
if (ret)
goto err_bridge_remove;
return 0;
/*
* If devm_of_dp_aux_populate_bus() returns -ENODEV then it's up to
* usa to call ps8640_bridge_link_panel() directly. NOTE: in this case
* the function is allowed to -EPROBE_DEFER.
*/
if (ret == -ENODEV)
return ps8640_bridge_link_panel(&ps_bridge->aux);
err_bridge_remove:
drm_bridge_remove(&ps_bridge->bridge);
return ret;
}
static int ps8640_remove(struct i2c_client *client)
{
struct ps8640 *ps_bridge = i2c_get_clientdata(client);
drm_bridge_remove(&ps_bridge->bridge);
return 0;
}
static const struct of_device_id ps8640_match[] = {
{ .compatible = "parade,ps8640" },
{ }
......@@ -702,7 +721,6 @@ MODULE_DEVICE_TABLE(of, ps8640_match);
static struct i2c_driver ps8640_driver = {
.probe_new = ps8640_probe,
.remove = ps8640_remove,
.driver = {
.name = "ps8640",
.of_match_table = ps8640_match,
......
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