backlight: qcom-wled: Fix unbalanced OVP IRQ enable at probe

wled_configure_ovp_irq() derives the initial state of the OVP interrupt
from the hardware:

        /* Keep OVP irq disabled until module is enabled */
        if (!(val & WLED3_CTRL_REG_MOD_EN_MASK))
                disable_irq(wled->ovp_irq);

but wled->brightness, which is what the rest of the driver uses to tell
whether the module is on, is left at zero.

On boards where the bootloader hands the kernel a lit backlight the two
disagree. MOD_EN is already set, so the interrupt is left enabled, while
wled_update_status() still believes the backlight is off and takes

        if (!!brightness != !!wled->brightness)
                rc = wled_module_enable(wled, !!brightness);

on the first backlight update. wled_module_enable() then schedules
wled_ovp_work(), which calls enable_irq() on the already enabled
interrupt:

  Unbalanced enable for IRQ 176
  WARNING: CPU: 0 PID: 160 at kernel/irq/manage.c:774 __enable_irq+0x50/0x80
  Hardware name: Xiaomi Pocophone F1 (DT)
  Workqueue: events wled_ovp_work
  Call trace:
   __enable_irq+0x50/0x80
   enable_irq+0x48/0xa0
   wled_ovp_work+0x18/0x24
   process_one_work+0x1d0/0x350
   worker_thread+0x13c/0x460
   kthread+0x110/0x114
   ret_from_fork+0x10/0x20

The bootloader is not the only way to get there. The readback runs after
wledN_setup(), and wled4_setup() sets MOD_EN itself on the path where the
sink configuration does not already match, as does the tail of
wled_auto_string_detection(), which all three setup paths can reach
through wled_auto_detection_at_init(). A cold-booted board with a dark
panel can therefore reach the same disagreement.

Move the MOD_EN readback into wled_probe() and use it to seed
wled->brightness, so the driver starts out agreeing with the hardware,
and key the OVP interrupt off wled->brightness instead. The first
backlight update then only reprograms the brightness registers and
leaves both the module and the interrupt alone. The OVP interrupt also
stays armed from probe whenever the module is already enabled, rather
than being disabled at probe and only enabled once something writes
brightness.

Note that a backlight update requesting brightness 0 before any non-zero
one now really does turn the module off wherever MOD_EN was already set,
where before it was silently ignored.

wled->brightness is seeded with default-brightness rather than the level
the bootloader actually programmed, so the first update can still step
the brightness. Reading that level back is version specific and is done
in a follow-up, to keep this fix small enough to backport.

Assisted-by: LLM
Fixes: 8663c188beea ("backlight: qcom-wled: Add auto string detection logic")
Cc: stable@vger.kernel.org
Signed-off-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Daniel Thompson (RISCstar) <danielt@kernel.org>
Link: https://patch.msgid.link/20260921-qcom-wled-backlight-v4-3-bab8c7ef73cb@ixit.cz
Signed-off-by: Lee Jones <lee@kernel.org>

0 files changed, 0 insertions, 0 deletions