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

[Maxim Schwalm <maxim.schwalm@gmail.com>]

On 14.08.23 12:04, Tomi Valkeinen wrote:
> 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 ]---
> 
> Hi Maxim,
> 
> Can you try the attached patch (on top of the series)? If it helps, I'll 
> refresh the series with the fix.
> 

Thanks, Tomi! This fixes the issue.

Best regards,
Maxim