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

[Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>]

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@ideasonboard.com>
>> ---
>>   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