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Message-Id: <20220503153850.v2.2.Ia6324ebc848cd40b4dbd3ad3289a7ffb5c197779@changeid>
Date: Tue, 3 May 2022 15:40:29 -0700
From: Douglas Anderson <dianders@...omium.org>
To: dri-devel@...ts.freedesktop.org
Cc: Philip Chen <philipchen@...omium.org>,
Sankeerth Billakanti <quic_sbillaka@...cinc.com>,
Stephen Boyd <swboyd@...omium.org>,
freedreno@...ts.freedesktop.org, linux-arm-msm@...r.kernel.org,
Hsin-Yi Wang <hsinyi@...omium.org>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
Robert Foss <robert.foss@...aro.org>,
Abhinav Kumar <quic_abhinavk@...cinc.com>,
Douglas Anderson <dianders@...omium.org>,
Andrzej Hajda <andrzej.hajda@...el.com>,
Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...ux.ie>,
Jernej Skrabec <jernej.skrabec@...il.com>,
Jonas Karlman <jonas@...boo.se>,
Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
Neil Armstrong <narmstrong@...libre.com>,
linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/2] 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
a1e3667a9835 ("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: Douglas Anderson <dianders@...omium.org>
---
Changes in v2:
- Rewrote atop new method introduced by patch #1.
drivers/gpu/drm/bridge/parade-ps8640.c | 77 +++++++++++++++++---------
1 file changed, 52 insertions(+), 25 deletions(-)
diff --git a/drivers/gpu/drm/bridge/parade-ps8640.c b/drivers/gpu/drm/bridge/parade-ps8640.c
index edb939b14c04..68131ca91eac 100644
--- a/drivers/gpu/drm/bridge/parade-ps8640.c
+++ b/drivers/gpu/drm/bridge/parade-ps8640.c
@@ -104,6 +104,7 @@ struct ps8640 {
struct gpio_desc *gpio_powerdown;
struct device_link *link;
bool pre_enabled;
+ bool bridge_added;
};
static const struct regmap_config ps8640_regmap_config[] = {
@@ -537,12 +538,11 @@ 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;
struct mipi_dsi_host *host;
- int ret;
const struct mipi_dsi_device_info info = { .type = "ps8640",
.channel = 0,
.node = NULL,
@@ -577,17 +577,44 @@ static int ps8640_bridge_host_attach(struct device *dev, struct ps8640 *ps_bridg
dsi->format = MIPI_DSI_FMT_RGB888;
dsi->lanes = NUM_MIPI_LANES;
- ret = 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 we don't have our panel
+ * under the "aux-bus". 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);
+
+ drm_bridge_add(&ps_bridge->bridge);
+
+ ret = devm_mipi_dsi_attach(dev, ps_bridge->dsi);
if (ret)
- return ret;
+ drm_bridge_remove(&ps_bridge->bridge);
+ else
+ ps_bridge->bridge_added = true;
- return 0;
+ return ret;
}
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;
@@ -628,6 +655,14 @@ 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);
@@ -670,31 +705,23 @@ static int ps8640_probe(struct i2c_client *client)
if (ret)
return ret;
- devm_of_dp_aux_populate_ep_devices(&ps_bridge->aux);
-
- /* 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;
-
-err_bridge_remove:
- drm_bridge_remove(&ps_bridge->bridge);
- return ret;
+ /*
+ * Kick off the probe for our panel if it's on the dp-aux bus.
+ * If the panel is on the aux bus ps8640_bridge_link_panel() will
+ * get called when it finishes probing. If the panel is an old-style
+ * platform device ps8640_bridge_link_panel() will be called directly
+ * and its return value will be the return value of our function.
+ */
+ return devm_of_dp_aux_populate_ep_device(&ps_bridge->aux,
+ ps8640_bridge_link_panel);
}
static int ps8640_remove(struct i2c_client *client)
{
struct ps8640 *ps_bridge = i2c_get_clientdata(client);
- drm_bridge_remove(&ps_bridge->bridge);
+ if (ps_bridge->bridge_added)
+ drm_bridge_remove(&ps_bridge->bridge);
return 0;
}
--
2.36.0.464.gb9c8b46e94-goog
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