From: David Heidelberg <[email protected]>
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 needs a per-version accessor and
is left for later.
Assisted-by: LLM
Fixes: 8663c188beea ("backlight: qcom-wled: Add auto string detection logic")
Cc: [email protected]
Signed-off-by: David Heidelberg <[email protected]>
---
this is slightly annoying bug sdm845-mainline had patched for a years,
but not very well. This should be the proper patch, got ack from people
with Xiaomi Poco F1 (ebbg variant) which does use this so it works.
Adding MSM8953 folks into Cc too, which use the early fix.
---
drivers/video/backlight/qcom-wled.c | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)
diff --git a/drivers/video/backlight/qcom-wled.c
b/drivers/video/backlight/qcom-wled.c
index 650dd95f06ef5..344b8cad90105 100644
--- a/drivers/video/backlight/qcom-wled.c
+++ b/drivers/video/backlight/qcom-wled.c
@@ -1622,54 +1622,49 @@ static int wled_configure_short_irq(struct wled *wled,
return rc;
}
static int wled_configure_ovp_irq(struct wled *wled,
struct platform_device *pdev)
{
int rc;
- u32 val;
wled->ovp_irq = platform_get_irq_byname(pdev, "ovp");
if (wled->ovp_irq < 0) {
dev_dbg(&pdev->dev, "OVP IRQ not found - disabling automatic
string detection\n");
return 0;
}
rc = devm_request_threaded_irq(wled->dev, wled->ovp_irq, NULL,
wled_ovp_irq_handler, IRQF_ONESHOT,
"wled_ovp_irq", wled);
if (rc < 0) {
wled->ovp_irq = 0;
return 0;
}
- rc = regmap_read(wled->regmap, wled->ctrl_addr +
- WLED3_CTRL_REG_MOD_EN, &val);
- if (rc < 0)
- return rc;
-
- /* Keep OVP irq disabled until module is enabled */
- if (!(val & WLED3_CTRL_REG_MOD_EN_MASK))
+ /* Keep the OVP irq disabled until the module is enabled */
+ if (!wled->brightness)
disable_irq(wled->ovp_irq);
return 0;
}
static const struct backlight_ops wled_ops = {
.update_status = wled_update_status,
};
static int wled_probe(struct platform_device *pdev)
{
struct backlight_properties props;
struct backlight_device *bl;
struct wled *wled;
struct regmap *regmap;
+ u32 mod_en;
u32 val;
int rc;
regmap = dev_get_regmap(pdev->dev.parent, NULL);
if (!regmap) {
dev_err(&pdev->dev, "Unable to get regmap\n");
return -EINVAL;
}
@@ -1729,27 +1724,42 @@ static int wled_probe(struct platform_device *pdev)
default:
dev_err(wled->dev, "Invalid WLED version\n");
break;
}
INIT_DELAYED_WORK(&wled->ovp_work, wled_ovp_work);
+ val = WLED_DEFAULT_BRIGHTNESS;
+ of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);
+
+ /*
+ * The module may already be enabled, either by a bootloader that left
+ * the backlight lit or by the setup above. Record that, so that the
+ * first brightness update does not enable an already enabled module,
+ * and so that the OVP irq is armed from probe rather than from that
+ * first update.
+ */
+ rc = regmap_read(wled->regmap, wled->ctrl_addr + WLED3_CTRL_REG_MOD_EN,
+ &mod_en);
+ if (rc < 0)
+ return rc;
+
+ if (mod_en & WLED3_CTRL_REG_MOD_EN_MASK)
+ wled->brightness = val;
+
rc = wled_configure_short_irq(wled, pdev);
if (rc < 0)
return rc;
rc = wled_configure_ovp_irq(wled, pdev);
if (rc < 0)
return rc;
- val = WLED_DEFAULT_BRIGHTNESS;
- of_property_read_u32(pdev->dev.of_node, "default-brightness", &val);
-
memset(&props, 0, sizeof(struct backlight_properties));
props.type = BACKLIGHT_RAW;
props.brightness = val;
props.max_brightness = wled->max_brightness;
bl = devm_backlight_device_register(&pdev->dev, wled->name,
&pdev->dev, wled,
&wled_ops, &props);
return PTR_ERR_OR_ZERO(bl);
---
base-commit: 944a035ecca915ae947905dcfb03f2b9dc6d032c
change-id: 20260908-qcom-wled-backlight-fd9574027353
Best regards,
--
David Heidelberg <[email protected]>
