[PATCH v2 0/4] drm: panel: Fix atomic helper-induced regressions

[Linus Walleij <linus.walleij@linaro.org>]

commit c9b1150a68d9362a0827609fc0dc1664c0d8bfe1
"drm/atomic-helper: Re-order bridge chain pre-enable and post-disable"
caused a series of regressions in all panels that send
DSI commands in their .prepare() and .unprepare()
callbacks.

As the CRTC is no longer online at bridge_pre_enable()
and gone at brige_post_disable() which maps to the panel
bridge .prepare()/.unprepare() callbacks, any CRTC that
enable/disable the DSI transmitter in it's enable/disable
callbacks will be unable to send any DSI commands in the
.prepare() and .unprepare() callbacks.

This is also evident from device trees with the DSI
inside the CRTC such as this:

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

   dsi@a0351000 {
     panel {
       compatible = "hydis,hva40wv1", "novatek,nt35510";
       reg = <0>;
       vdd-supply = <&ab8500_ldo_aux4_reg>;
       vddi-supply = <&ab8500_ldo_aux6_reg>;
    };
  };
};

The panel is inside the DSI which is inside the CRTC
(MCDE).

This is in a way natural, so let's just fix it in all
affected panel drivers that I know of and can test.
Mostly Ux500 phones, and only those with the display
directly on DSI (not e.g. using DPI and SPI).

Other panel drivers may be affected.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
Changes in v2:
- Fix half-baked NT35510 patch that was still sending init commands
  in the prepare() callback.
- Link to v1: https://lore.kernel.org/r/20251023-fix-mcde-drm-regression-v1-0-ed9a925db8c7@linaro.org

---
Linus Walleij (4):
      drm: panel: nt355510: Move DSI commands to enable/disable
      drm: panel: s6d16d0: Move DSI commands to enable/disable
      drm: panel: nt35560: Move DSI commands to enable/disable
      drm: panel: s6e63m0: Move DSI commands to enable/disable

 drivers/gpu/drm/panel/panel-novatek-nt35510.c | 31 +++++++++++++++++++-----
 drivers/gpu/drm/panel/panel-novatek-nt35560.c | 24 ++++++++++++------
 drivers/gpu/drm/panel/panel-samsung-s6d16d0.c | 35 ++++++++++++---------------
 drivers/gpu/drm/panel/panel-samsung-s6e63m0.c | 31 +++++++++---------------
 4 files changed, 70 insertions(+), 51 deletions(-)
---
base-commit: 6548d364a3e850326831799d7e3ea2d7bb97ba08
change-id: 20251022-fix-mcde-drm-regression-c9ac0cc20bae

Best regards,
-- 
Linus Walleij <linus.walleij@linaro.org>