Re: [PATCH 11/11] drm/bridge: tc358768: Add DRM_BRIDGE_ATTACH_NO_CONNECTOR support

From: Tomi Valkeinen
Date: Mon Aug 14 2023 - 03:32:59 EST

On 13/08/2023 20:11, Maxim Schwalm wrote:
On 04.08.23 12:44, Tomi Valkeinen wrote:
Signed-off-by: Tomi Valkeinen <tomi.valkeinen@xxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/bridge/tc358768.c | 64 +++++++++++++++++++++++++++------------
1 file changed, 45 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/bridge/tc358768.c b/drivers/gpu/drm/bridge/tc358768.c
index ea19de5509ed..a567f136ddc7 100644
--- a/drivers/gpu/drm/bridge/tc358768.c
+++ b/drivers/gpu/drm/bridge/tc358768.c
@@ -131,8 +131,17 @@ static const char * const tc358768_supplies[] = {
struct tc358768_dsi_output {
struct mipi_dsi_device *dev;
+
+ /* Legacy field if DRM_BRIDGE_ATTACH_NO_CONNECTOR is not used */
struct drm_panel *panel;
- struct drm_bridge *bridge;
+
+ /*
+ * If DRM_BRIDGE_ATTACH_NO_CONNECTOR is not used and a panel is attached
+ * to tc358768, 'next_bridge' contains the bridge the driver created
+ * with drm_panel_bridge_add_typed(). Otherwise 'next_bridge' contains
+ * the next bridge the driver found.
+ */
+ struct drm_bridge *next_bridge;
};
struct tc358768_priv {
@@ -391,8 +400,6 @@ static int tc358768_dsi_host_attach(struct mipi_dsi_host *host,
struct mipi_dsi_device *dev)
{
struct tc358768_priv *priv = dsi_host_to_tc358768(host);
- struct drm_bridge *bridge;
- struct drm_panel *panel;
struct device_node *ep;
int ret;
@@ -420,21 +427,7 @@ static int tc358768_dsi_host_attach(struct mipi_dsi_host *host,
return -ENOTSUPP;
}
- ret = drm_of_find_panel_or_bridge(host->dev->of_node, 1, 0, &panel,
- &bridge);
- if (ret)
- return ret;
-
- if (panel) {
- bridge = drm_panel_bridge_add_typed(panel,
- DRM_MODE_CONNECTOR_DSI);
- if (IS_ERR(bridge))
- return PTR_ERR(bridge);
- }
-
priv->output.dev = dev;
- priv->output.bridge = bridge;
- priv->output.panel = panel;
priv->dsi_lanes = dev->lanes;
priv->dsi_bpp = mipi_dsi_pixel_format_to_bpp(dev->format);
@@ -463,7 +456,7 @@ static int tc358768_dsi_host_detach(struct mipi_dsi_host *host,
drm_bridge_remove(&priv->bridge);
if (priv->output.panel)
- drm_panel_bridge_remove(priv->output.bridge);
+ drm_panel_bridge_remove(priv->output.next_bridge);
return 0;
}
@@ -544,7 +537,40 @@ static int tc358768_bridge_attach(struct drm_bridge *bridge,
return -ENOTSUPP;
}
- return drm_bridge_attach(bridge->encoder, priv->output.bridge, bridge,
+ if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR) {
+ struct device_node *node;
+
+ /* Get the next bridge, connected to port@1. */
+ node = of_graph_get_remote_node(priv->dev->of_node, 1, -1);
+ if (!node)
+ return -ENODEV;
+
+ priv->output.next_bridge = of_drm_find_bridge(node);
+ of_node_put(node);
+ if (!priv->output.next_bridge)
+ return -EPROBE_DEFER;
+ } else {
+ struct drm_bridge *bridge;
+ struct drm_panel *panel;
+ int ret;
+
+ ret = drm_of_find_panel_or_bridge(priv->dev->of_node, 1, 0,
+ &panel, &bridge);
+ if (ret)
+ return ret;
+
+ if (panel) {
+ bridge = drm_panel_bridge_add_typed(panel,
+ DRM_MODE_CONNECTOR_DSI);
+ if (IS_ERR(bridge))
+ return PTR_ERR(bridge);
+ }
+
+ priv->output.next_bridge = bridge;
+ priv->output.panel = panel;
+ }
+
+ return drm_bridge_attach(bridge->encoder, priv->output.next_bridge, bridge,
flags);
}

This patch unfortunately breaks the display output on the Asus TF700T:

[drm:drm_bridge_attach] *ERROR* failed to attach bridge /i2c-mux/i2c@1/dsi@7 to encoder LVDS-59: -517
tegra-dc 54200000.dc: failed to initialize RGB output: -517
drm drm: failed to initialize 54200000.dc: -517
------------[ cut here ]------------
WARNING: CPU: 3 PID: 69 at lib/refcount.c:28 tegra_dc_init+0x24/0x5fc
refcount_t: underflow; use-after-free.
Modules linked in: elants_i2c panel_simple tc358768 atkbd vivaldi_fmap
CPU: 3 PID: 69 Comm: kworker/u8:6 Not tainted 6.5.0-rc2-postmarketos-grate #95
Hardware name: NVIDIA Tegra SoC (Flattened Device Tree)
Workqueue: events_unbound deferred_probe_work_func
unwind_backtrace from show_stack+0x10/0x14
show_stack from dump_stack_lvl+0x40/0x4c
dump_stack_lvl from __warn+0x94/0xc0
__warn from warn_slowpath_fmt+0x118/0x16c
warn_slowpath_fmt from tegra_dc_init+0x24/0x5fc
tegra_dc_init from host1x_device_init+0x84/0x15c
host1x_device_init from host1x_drm_probe+0xd8/0x3c4
host1x_drm_probe from really_probe+0xc8/0x2dc
really_probe from __driver_probe_device+0x88/0x19c
__driver_probe_device from driver_probe_device+0x30/0x104
driver_probe_device from __device_attach_driver+0x94/0x108
__device_attach_driver from bus_for_each_drv+0x80/0xb8
bus_for_each_drv from __device_attach+0xa0/0x190
__device_attach from bus_probe_device+0x88/0x8c
bus_probe_device from deferred_probe_work_func+0x78/0xa4
deferred_probe_work_func from process_one_work+0x208/0x420
process_one_work from worker_thread+0x54/0x550
worker_thread from kthread+0xdc/0xf8
kthread from ret_from_fork+0x14/0x2c
Exception stack(0xcf9c5fb0 to 0xcf9c5ff8)
5fa0: 00000000 00000000 00000000 00000000
5fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
---[ end trace 0000000000000000 ]---

Sounds like the Tegra driver has issues cleaning up after getting a EPROBE_DEFER.

The tc358768 driver might have an issue with a setup where a panel is directly attached to it. I don't have such a setup, but maybe I can fake it just to see if the probing goes ok.

Tomi