Pinetab 2 screen no longer coming on

[fxc]

I received my Pinetab 2 (ARM version) in early June and the screen worked fine. The screen would go off due to power saving but tapping the screen or keys would bring the screen on again after a bit. However, I was using the Pinetab 2 with the screen working, I left for a few minutes and on return the screen was off. When I tried tapping the screen or keys then the screen didn't come on. Now the screen is always blank/black whatever I try. I've tried the brightness key (Fn+F2) many times, tried rebooting, powering off and then back on again, tried tapping the screen and keys. The keyboard backlight, not the LCD backlight, still works so the keyboard must still be being powered and does work, see later. I've attached the serial dongle and the Pinetab 2 does boot up and systemctl shows the displayer manager, sddm.service - Simple Desktop Display Manager, active. If I type the password on the keyboard and press enter, although there is still nothing on the built-in display, I can see that the user has logged in on the serial console!
Further, I've attached an external monitor via the HDMI port and it displays on external monitor fine.  When I played with removing and then adding back the built-in screen the GUI had lock-ups for a few seconds at a time.
There are error message in `dmesg`:

Code:

[    0.952428] rockchip-drm display-subsystem: bound fe060000.dsi (ops dw_mipi_dsi_rockchip_ops)
[    0.954580] [drm] Initialized rockchip 1.0.0 20140818 for display-subsystem on minor 0
[    0.954939] ------------[ cut here ]------------
[    0.954958] WARNING: CPU: 2 PID: 748 at drivers/gpu/drm/drm_mode_object.c:45 drm_mode_object_add+0x90/0x98
[    0.954990] Modules linked in:
[    0.955007] CPU: 2 PID: 748 Comm: kworker/u8:4 Not tainted 6.3.0-5-danctnix #1
[    0.955021] Hardware name: Pine64 PineTab2 v2.0 (DT)
[    0.955031] Workqueue: events_unbound deferred_probe_work_func
[    0.955050] pstate: 60400009 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[    0.955063] pc : drm_mode_object_add+0x90/0x98
[    0.955075] lr : drm_property_create+0xd0/0x188
[snip]
[    0.955300] Call trace:
[    0.955307]  drm_mode_object_add+0x90/0x98
[    0.955320]  drm_property_create+0xd0/0x188
[    0.955334]  drm_property_create_enum+0x30/0x94
[    0.955348]  drm_connector_set_panel_orientation+0x94/0xb4
[    0.955366]  boe_get_modes+0x70/0xbc
[    0.955386]  drm_panel_get_modes+0x28/0x48
[    0.955399]  panel_bridge_connector_get_modes+0x1c/0x2c
[    0.955418]  drm_helper_probe_single_connector_modes+0x1a4/0x52c
[    0.955433]  drm_client_modeset_probe+0x204/0x1194
[    0.955448]  __drm_fb_helper_initial_config_and_unlock+0x54/0x4b0
[    0.955464]  drm_fb_helper_initial_config+0x4c/0x60
[    0.955480]  drm_fbdev_client_hotplug+0x8c/0xd8
[    0.955495]  drm_fbdev_generic_setup+0x90/0x170
[    0.955509]  rockchip_drm_bind+0x1ec/0x208
[    0.955521]  try_to_bring_up_aggregate_device+0x170/0x1c0
[    0.955536]  __component_add+0xa8/0x174
[    0.955548]  component_add+0x18/0x28
[    0.955560]  dw_mipi_dsi_rockchip_host_attach+0x5c/0x14c
[    0.955577]  dw_mipi_dsi_host_attach+0x98/0xcc
[    0.955593]  mipi_dsi_attach+0x2c/0x44
[    0.955609]  boe_dsi_probe+0xf8/0x1a0
[    0.955623]  mipi_dsi_drv_probe+0x24/0x34
[    0.955639]  really_probe+0x150/0x2b4
[    0.955651]  __driver_probe_device+0x7c/0xe8
[    0.955663  driver_probe_device+0x40/0x164
[    0.955674]  __device_attach_driver+0xc4/0x144
[    0.955687]  bus_for_each_drv+0x88/0xe8
[    0.955702]  __device_attach+0xa0/0x190
[    0.955713]  device_initial_probe+0x18/0x28
[    0.955724]  bus_probe_device+0xb0/0xb4
[    0.955734]  deferred_probe_work_func+0x88/0xc4
[    0.955744]  process_one_work+0x1dc/0x340
[    0.955761]  worker_thread+0x224/0x434
[    0.955773]  kthread+0x10c/0x110
[    0.955785]  ret_from_fork+0x10/0x20
[    0.955800] ---[ end trace 0000000000000000 ]---
[    0.955858] ------------[ cut here ]------------
[    0.955866] WARNING: CPU: 2 PID: 748 at drivers/gpu/drm/drm_mode_object.c:242 drm_object_attach_property+0x6c/0xb8

and later

Code:

[  40.019376] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 282624 bytes), total 32768 (slots), used 0 (slots)
[  40.056213] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 1048576 bytes), total 32768 (slots), used 18 (slots)
[  40.068669] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 1011712 bytes), total 32768 (slots), used 0 (slots)
[  40.251994] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 987136 bytes), total 32768 (slots), used 2326 (slots)
[  40.277979] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 540672 bytes), total 32768 (slots), used 0 (slots)
[  40.358499] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 1667072 bytes), total 32768 (slots), used 92 (slots)
[  40.445645] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 552960 bytes), total 32768 (slots), used 2330 (slots)
[  50.903840] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 831488 bytes), total 32768 (slots), used 430 (slots)
[  50.946254] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 3350528 bytes), total 32768 (slots), used 140 (slots)
[  50.990632] rockchip-drm display-subsystem: swiotlb buffer is full (sz: 5324800 bytes), total 32768 (slots), used 0 (slots)

The touchscreen works because I can do gestures on the screen and they effect the desktop as seen via HDMI.
I've installed the latest updates which included an initramfs rebuild but made no difference.
I've reinstalled the kernel but this has made no difference.

Code:

Linux danctnix 6.3.0-5-danctnix #1 SMP PREEMPT_DYNAMIC Mon Jun 12 06:40:39 UTC 2023 aarch64 GNU/Linux

I'm pretty sure this is a hardware fault.  I've reported the issue to Pine64 support and they have recommended coming here for further diagnosis and will RMA if it is a hardware fault so I appreciate any help on diagnosing this issue.

It's likely a faulty display unit. To be sure please try to reflash the factory image. If the issue persists then it is relatively safe it was not a bad flash at the factory. For details see https://wiki.pine64.org/wiki/PineTab2#Software.