Re: [PATCH v3] drm/bridge: panel: Add a device link between drm device and panel device

[Linus Walleij]

On Mon, Aug 7, 2023 at 8:06 AM Liu Ying <victor.liu@xxxxxxx> wrote:

> Add the device link when panel bridge is attached and delete the link
> when panel bridge is detached.  The drm device is the consumer while
> the panel device is the supplier.  This makes sure that the drm device
> suspends eariler and resumes later than the panel device, hence resolves
> problems where the order is reversed, like the problematic case mentioned
> in the below link.
>
> Link: https://lore.kernel.org/lkml/CAPDyKFr0XjrU_udKoUKQ_q8RWaUkyqL+8fV-7s1CTMqi7u3-Rg@xxxxxxxxxxxxxx/T/
> Suggested-by: Ulf Hansson <ulf.hansson@xxxxxxxxxx>
> Signed-off-by: Liu Ying <victor.liu@xxxxxxx>
> ---
> v2->v3:
> * Improve commit message s/swapped/reversed/.

This patch causes a regression in the Ux500 MCDE
drivers/gpu/drm/mcde/* driver with the nt35510 panel
drivers/gpu/drm/panel/panel-novatek-nt35510.c
my dmesg looks like this:

[    1.678680] mcde a0350000.mcde: MCDE clk rate 199680000 Hz
[    1.684448] mcde a0350000.mcde: found MCDE HW revision 3.0 (dev 8,
metal fix 0)
[    1.692840] mcde-dsi a0351000.dsi: HW revision 0x02327457
[    1.699310] mcde-dsi a0351000.dsi: attached DSI device with 2 lanes
[    1.705627] mcde-dsi a0351000.dsi: format 00000000, 24bpp
[    1.711059] mcde-dsi a0351000.dsi: mode flags: 00000400
[    1.716400] mcde-dsi a0351000.dsi: registered DSI host
[    1.722473] mcde-dsi a0352000.dsi: HW revision 0x02327457
[    1.727874] mcde-dsi a0352000.dsi: registered DSI host
[    1.733734] mcde-dsi a0353000.dsi: HW revision 0x02327457
[    1.739135] mcde-dsi a0353000.dsi: registered DSI host
[    1.814971] mcde-dsi a0351000.dsi: connected to panel
[    1.820037] mcde-dsi a0351000.dsi: initialized MCDE DSI bridge
[    1.825958] mcde a0350000.mcde: bound a0351000.dsi (ops
mcde_dsi_component_ops)
[    1.833312] mcde-dsi a0352000.dsi: unused DSI interface
[    1.838531] mcde a0350000.mcde: bound a0352000.dsi (ops
mcde_dsi_component_ops)
[    1.845886] mcde-dsi a0353000.dsi: unused DSI interface
[    1.851135] mcde a0350000.mcde: bound a0353000.dsi (ops
mcde_dsi_component_ops)
[    1.858917] [drm:panel_bridge_attach] *ERROR* Failed to add device
link between a0350000.mcde and a0351000.dsi.0
[    1.869171] [drm:drm_bridge_attach] *ERROR* failed to attach bridge
/soc/mcde@a0350000/dsi@a0351000/panel to encoder None-34: -22
[    1.880920] [drm:drm_bridge_attach] *ERROR* failed to attach bridge
/soc/mcde@a0350000/dsi@a0351000 to encoder None-34: -22
[    1.892120] mcde a0350000.mcde: failed to attach display output bridge
[    1.898773] mcde a0350000.mcde: adev bind failed: -22
[    1.903991] mcde a0350000.mcde: failed to add component master
[    1.909912] mcde: probe of a0350000.mcde failed with error -22
[    1.916656] ------------[ cut here ]------------
[    1.921295] WARNING: CPU: 1 PID: 1 at drivers/regulator/core.c:2996
_regulator_disable+0x130/0x190
[    1.930297] unbalanced disables for AUX6
[    1.934265] Modules linked in:
[    1.937347] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
6.6.0-08649-g7d461b291e65 #3
[    1.944915] Hardware name: ST-Ericsson Ux5x0 platform (Device Tree Support)
[    1.951873]  unwind_backtrace from show_stack+0x10/0x14
[    1.957122]  show_stack from dump_stack_lvl+0x40/0x4c
[    1.962188]  dump_stack_lvl from __warn+0x84/0xc8
[    1.966918]  __warn from warn_slowpath_fmt+0x124/0x190
[    1.972076]  warn_slowpath_fmt from _regulator_disable+0x130/0x190
[    1.978271]  _regulator_disable from regulator_bulk_disable+0x5c/0x100
[    1.984802]  regulator_bulk_disable from nt35510_remove+0x1c/0x58
[    1.990905]  nt35510_remove from mipi_dsi_drv_remove+0x18/0x20
[    1.996765]  mipi_dsi_drv_remove from
device_release_driver_internal+0x184/0x1f8
[    2.004180]  device_release_driver_internal from bus_remove_device+0xc0/0xe4
[    2.011230]  bus_remove_device from device_del+0x14c/0x464
[    2.016723]  device_del from device_unregister+0xc/0x20
[    2.021972]  device_unregister from mipi_dsi_remove_device_fn+0x34/0x3c
[    2.028594]  mipi_dsi_remove_device_fn from device_for_each_child+0x64/0xa4
[    2.035583]  device_for_each_child from mipi_dsi_host_unregister+0x24/0x50
[    2.042480]  mipi_dsi_host_unregister from platform_remove+0x20/0x5c
[    2.048858]  platform_remove from device_release_driver_internal+0x184/0x1f8
[    2.055908]  device_release_driver_internal from bus_remove_device+0xc0/0xe4
[    2.062957]  bus_remove_device from device_del+0x14c/0x464
[    2.068450]  device_del from platform_device_del.part.0+0x10/0x74
[    2.074554]  platform_device_del.part.0 from
platform_device_unregister+0x18/0x24
[    2.082061]  platform_device_unregister from
of_platform_device_destroy+0x9c/0xac
[    2.089569]  of_platform_device_destroy from
device_for_each_child_reverse+0x78/0xbc
[    2.097320]  device_for_each_child_reverse from
devm_of_platform_populate_release+0x34/0x48
[    2.105682]  devm_of_platform_populate_release from
devres_release_all+0x94/0xf8
[    2.113098]  devres_release_all from device_unbind_cleanup+0xc/0x60
[    2.119384]  device_unbind_cleanup from really_probe+0x1a0/0x2d8
[    2.125396]  really_probe from __driver_probe_device+0x84/0xd4
[    2.131225]  __driver_probe_device from driver_probe_device+0x30/0x104
[    2.137756]  driver_probe_device from __driver_attach+0x90/0x178
[    2.143768]  __driver_attach from bus_for_each_dev+0x7c/0xcc
[    2.149444]  bus_for_each_dev from bus_add_driver+0xcc/0x1cc
[    2.155120]  bus_add_driver from driver_register+0x7c/0x114
[    2.160705]  driver_register from do_one_initcall+0x5c/0x190
[    2.166381]  do_one_initcall from kernel_init_freeable+0x1f8/0x250
[    2.172576]  kernel_init_freeable from kernel_init+0x18/0x12c
[    2.178344]  kernel_init from ret_from_fork+0x14/0x28
[    2.183410] Exception stack(0xf08c5fb0 to 0xf08c5ff8)
[    2.188446] 5fa0:                                     00000000
00000000 00000000 00000000
[    2.196624] 5fc0: 00000000 00000000 00000000 00000000 00000000
00000000 00000000 00000000
[    2.204803] 5fe0: 00000000 00000000 00000000 00000000 00000013 00000000
[    2.211486] ---[ end trace 0000000000000000 ]---
[    2.216125] Failed to disable vddi: -EIO
[    2.220062] panel-novatek-nt35510 a0351000.dsi.0: Failed to power off

Reverting the patch solves the problem.

See device tree at e.g.:
arch/arm/boot/dts/st/ste-ux500-samsung-skomer.dts

The usual problems with patches like this is that our DSI panel
is attached in the DT without any graph:

                mcde@a0350000 {
                        status = "okay";
                        pinctrl-names = "default";
                        pinctrl-0 = <&dsi_default_mode>;

                        dsi@a0351000 {
                                panel {
                                        /* NT35510-based Hydis HVA40WV1 */
                                        compatible = "hydis,hva40wv1",
"novatek,nt35510";
                                        reg = <0>;
                                        /* v_lcd_3v0 2.3-4.8V */
                                        vdd-supply = <&ab8500_ldo_aux4_reg>;
                                        /* v_lcd_1v8 1.65-3.3V */
                                        vddi-supply = <&ab8500_ldo_aux6_reg>;
                                        /* GPIO 139 */
                                        reset-gpios = <&gpio4 11
GPIO_ACTIVE_LOW>;
                                        pinctrl-names = "default";
                                        pinctrl-0 = <&display_default_mode>;
                                        backlight = <&ktd253>;
                                };
                        };
                };

The DSI bridge is inside the display controller (MCDE) and the panel is
right inside the DSI bridge.

Suggestions welcome, I'm clueless why this happens.

Yours,
Linus Walleij