[PATCH 0/2] arm64: dts: qcom: Dell Inspiron 14 Plus 7441 backlight and touchscreen fixes

[PATCH 0/2] arm64: dts: qcom: Dell Inspiron 14 Plus 7441 backlight and touchscreen fixes

[Charlie Garner]

Two fixes for the Dell Inspiron 14 Plus 7441.

Patch 1 gives the eDP panel a PWM backlight. The AUO B140QAX01.H panel
only supports PWM-pin brightness, so the DP AUX fallback registers a
backlight with max_brightness 0 and brightness cannot be changed. The PWM
wiring (PMK8550 gpio5 func3, pmk8550_pwm) matches the HP OmniBook X14.
It goes in the Inspiron DT rather than x1-dell-thena.dtsi, because the
Latitude 7455 was submitted with a different panel and a working
backlight, and only the Inspiron has been tested. The dtsi only gains a
panel label, which leaves the Latitude DTB functionally unchanged. If a
Latitude 7455 owner can confirm the same PWM wiring, this can move to the
dtsi.

Patch 2 moves the touchscreen from 0x10, where nothing responds, to 0x09.
That is where the HID-over-I2C device answers, where the firmware's DSDT
places it on this machine, and where the Latitude 7455 DT already has the
same part.

As far as I know, no Inspiron 14 Plus 7441 has its touchscreen at 0x10.
The original node matches the CRD, XPS 13 9345 and T14s nodes the DT was
based on.

Charlie Garner (2):
  arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: add PWM
    backlight
  arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: fix touchscreen
    i2c address

 arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi   |  2 +-
 .../x1e80100-dell-inspiron-14-plus-7441.dts   | 31 +++++++++++++++++--
 2 files changed, 30 insertions(+), 3 deletions(-)


base-commit: 32afff1e816e10185bb571aa9d89dc2eb061d548
-- 
2.55.0

[PATCH 1/2] arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: add PWM backlight

[Charlie Garner]

The panel on the Dell Inspiron 14 Plus 7441 (AUO B140QAX01.H) cannot have
its brightness set over eDP AUX. DPCD 0x702 has BRIGHTNESS_PWM_PIN_CAP set
but BRIGHTNESS_AUX_SET_CAP clear:

	0x701 GENERAL_CAP_1            = 0x9b
	0x702 BACKLIGHT_ADJUSTMENT_CAP = 0x91   bit1 (AUX_SET) clear
	0x721 MODE_SET                 = 0x00   control mode: PWM pin

With no backlight phandle on the panel, panel-edp falls back to
drm_panel_dp_aux_backlight(). drm_edp_backlight_supported() only tests
0x701 bit0, which is set, so a backlight device is registered - but
drm_edp_backlight_probe_max() returns early when !aux_set, leaving max at
0:

	systemd-backlight: dp_aux_backlight: Maximum brightness is 0, ignoring device.
	gnome-shell: Backlight is unusable because the maximum brightness 0 is
	             bigger than minimum brightness 0

Brightness is driven by PWM instead. UEFI already configures the pad and
leaves it running, which is how the panel is lit before Linux touches it:

	gpiochip0 (c42d000.spmi:pmic@0:gpio@8800, PMK8550):
	  gpio5 : out low func3 vin-0 pull-down 10uA push-pull medium

and the corresponding LPG is present but disabled:

	pmic@0/pwm  qcom,pmk8550-pwm  status=disabled

This matches the PWM wiring of the HP OmniBook X14
(x1-hp-omnibook-x14.dtsi), so describe it the same way: enable
pmk8550_pwm, add the pinctrl state for gpio5 func3, and give the panel a
pwm-backlight.

The panel keeps its existing enable-gpios and edp_bl_en pinctrl, so power
sequencing is unchanged; only brightness control is added.

Keep this in the Inspiron DT rather than x1-dell-thena.dtsi. The Latitude
7455 shares the dtsi but was submitted with a different panel (BOE
NE14QDM) and a working backlight without any PWM description, and this
has only been tested on the Inspiron. Label the panel in the dtsi so the
board DT can attach the backlight, as the ThinkPad T14s LCD variant does.

Signed-off-by: Charlie Garner <charlie@akao.au>
---

Notes:
    If a Latitude 7455 owner can confirm the same PWM wiring on that machine,
    this can move to x1-dell-thena.dtsi.

 arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi   |  2 +-
 .../x1e80100-dell-inspiron-14-plus-7441.dts   | 27 +++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi b/arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi
index 2ebb42906c9b..ce31c9f5cd05 100644
--- a/arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi
+++ b/arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi
@@ -1039,7 +1039,7 @@ &mdss_dp3 {
 	status = "okay";
 
 	aux-bus {
-		panel {
+		panel: panel {
 			compatible = "edp-panel";
 			enable-gpios = <&tlmm 74 GPIO_ACTIVE_HIGH>;
 			power-supply = <&vreg_edp_3p3>;
diff --git a/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts b/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
index 75e10d97c386..5779a4e84522 100644
--- a/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
+++ b/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
@@ -10,6 +10,18 @@
 / {
 	model = "Dell Inspiron 14 Plus 7441";
 	compatible = "dell,inspiron-14-plus-7441", "qcom,x1e80100";
+
+	backlight: backlight {
+		compatible = "pwm-backlight";
+		pwms = <&pmk8550_pwm 0 5000000>;
+
+		brightness-levels = <0 2048 4096 8192 16384 65535>;
+		num-interpolated-steps = <20>;
+		default-brightness-level = <80>;
+
+		pinctrl-0 = <&edp_bl_pwm>;
+		pinctrl-names = "default";
+	};
 };
 
 &sound {
@@ -42,6 +54,21 @@ &iris {
 	status = "okay";
 };
 
+&panel {
+	backlight = <&backlight>;
+};
+
+&pmk8550_gpios {
+	edp_bl_pwm: edp-bl-pwm-state {
+		pins = "gpio5";
+		function = "func3";
+	};
+};
+
+&pmk8550_pwm {
+	status = "okay";
+};
+
 &remoteproc_adsp {
 	firmware-name = "qcom/x1e80100/dell/inspiron-14-plus-7441/qcadsp8380.mbn",
 			"qcom/x1e80100/dell/inspiron-14-plus-7441/adsp_dtbs.elf";
-- 
2.55.0

[PATCH 2/2] arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: fix touchscreen i2c address

[Charlie Garner]

The touchscreen is at i2c address 0x09, not 0x10. Nothing responds at 0x10,
so i2c_hid_of never probes and the panel does not work. tlmm pin 51, the
touchscreen interrupt, is left unclaimed as a result.

Scanning the bus shows only 0x09 responding (0x28 also ACKs but returns
zeros, presumably an alternate address on the same controller). Linux bus
0 here is the GENI I2C controller at 0xa80000, which is i2c8 in the DT:

	# i2cdetect -y -r 0
	00:          -- 09 -- -- -- -- -- --
	...

and 0x09 returns a valid HID-over-I2C descriptor:

	1e 00  descriptor length 30
	00 01  bcdVersion 1.00
	6b 03  report descriptor length 875
	...
	bd 29  vendor 0x29bd
	03 11  product 0x1103

whose report descriptor opens as a Windows Precision touchscreen:

	05 0d  Usage Page (Digitizer)
	09 04  Usage (Touch Screen)
	a1 01  Collection (Application)
	85 10  Report ID (0x10)
	05 0d  Usage Page (Digitizer)
	09 22  Usage (Finger)
	a1 02  Collection (Logical)
	09 42  Usage (Tip Switch)
	...    Contact Id, 16-bit X/Y, unit exponent -3

The firmware agrees. The DSDT describes one touchscreen, \_SB.TSC1, on
I2C9 (QUP_1_SE_0 at 0xa80000, i2c8 here) with its interrupt on GPIO 51.
Its _HID, slave address and HID descriptor address are placeholders that
UEFI fills in at boot, and on this machine they read LXST2021, 0x09 and
0x0001. Nothing at 0x28 is described. The Latitude 7455 DT already has the
same LXST2021 touchscreen at 0x09.

The original touchscreen@10 node is identical to the ones in
x1-crd.dtsi, x1e80100-dell-xps13-9345.dts and
x1e78100-lenovo-thinkpad-t14s.dtsi, which the Inspiron DT was based on.

Rename the node to match the corrected unit address.

Fixes: e7733b42111c ("arm64: dts: qcom: Add support for Dell Inspiron 7441 / Latitude 7455")
Signed-off-by: Charlie Garner <charlie@akao.au>
---

Notes:
    As far as I know, no Inspiron 14 Plus 7441 has its touchscreen at 0x10.
    The 7441 ships with a single touch display option, but the DSDT address is
    filled in by UEFI per unit, so please say if you have one that differs.

 .../boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts     | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts b/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
index 5779a4e84522..edbba5101b82 100644
--- a/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
+++ b/arch/arm64/boot/dts/qcom/x1e80100-dell-inspiron-14-plus-7441.dts
@@ -37,9 +37,9 @@ &gpu_zap_shader {
 };
 
 &i2c8 {
-	touchscreen@10 {
+	touchscreen@9 {
 		compatible = "hid-over-i2c";
-		reg = <0x10>;
+		reg = <0x9>;
 
 		hid-descr-addr = <0x1>;
 		interrupts-extended = <&tlmm 51 IRQ_TYPE_LEVEL_LOW>;
-- 
2.55.0

Re: [PATCH 0/2] arm64: dts: qcom: Dell Inspiron 14 Plus 7441 backlight and touchscreen fixes

[Bjorn Andersson]

On Thu, 24 Sep 2026 00:55:04 +0930, Charlie Garner wrote:
> Two fixes for the Dell Inspiron 14 Plus 7441.
> 
> Patch 1 gives the eDP panel a PWM backlight. The AUO B140QAX01.H panel
> only supports PWM-pin brightness, so the DP AUX fallback registers a
> backlight with max_brightness 0 and brightness cannot be changed. The PWM
> wiring (PMK8550 gpio5 func3, pmk8550_pwm) matches the HP OmniBook X14.
> It goes in the Inspiron DT rather than x1-dell-thena.dtsi, because the
> Latitude 7455 was submitted with a different panel and a working
> backlight, and only the Inspiron has been tested. The dtsi only gains a
> panel label, which leaves the Latitude DTB functionally unchanged. If a
> Latitude 7455 owner can confirm the same PWM wiring, this can move to the
> dtsi.
> 
> [...]

Applied, thanks!

[1/2] arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: add PWM backlight
      commit: 6f4139020847738d646db0b6589297f71fc0710c
[2/2] arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: fix touchscreen i2c address
      commit: 66de84159065c9c08be4ce17a8c016efa0382121

Best regards,
-- 
Bjorn Andersson <andersson@kernel.org>

Re: [PATCH 0/2] arm64: dts: qcom: Dell Inspiron 14 Plus 7441 backlight and touchscreen fixes

[Bjorn Andersson]

On Thu, Sep 24, 2026 at 12:55:04AM +0930, Charlie Garner wrote:
> Two fixes for the Dell Inspiron 14 Plus 7441.
> 
> Patch 1 gives the eDP panel a PWM backlight. The AUO B140QAX01.H panel
> only supports PWM-pin brightness, so the DP AUX fallback registers a
> backlight with max_brightness 0 and brightness cannot be changed. The PWM
> wiring (PMK8550 gpio5 func3, pmk8550_pwm) matches the HP OmniBook X14.
> It goes in the Inspiron DT rather than x1-dell-thena.dtsi, because the
> Latitude 7455 was submitted with a different panel and a working
> backlight, and only the Inspiron has been tested. The dtsi only gains a
> panel label, which leaves the Latitude DTB functionally unchanged. If a
> Latitude 7455 owner can confirm the same PWM wiring, this can move to the
> dtsi.
> 
> Patch 2 moves the touchscreen from 0x10, where nothing responds, to 0x09.
> That is where the HID-over-I2C device answers, where the firmware's DSDT
> places it on this machine, and where the Latitude 7455 DT already has the
> same part.
> 
> As far as I know, no Inspiron 14 Plus 7441 has its touchscreen at 0x10.
> The original node matches the CRD, XPS 13 9345 and T14s nodes the DT was
> based on.
> 
> Charlie Garner (2):
>   arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: add PWM
>     backlight
>   arm64: dts: qcom: x1e80100-dell-inspiron-14-plus-7441: fix touchscreen
>     i2c address
> 

Applied

Thank you,
Bjorn

>  arch/arm64/boot/dts/qcom/x1-dell-thena.dtsi   |  2 +-
>  .../x1e80100-dell-inspiron-14-plus-7441.dts   | 31 +++++++++++++++++--
>  2 files changed, 30 insertions(+), 3 deletions(-)
> 
> 
> base-commit: 32afff1e816e10185bb571aa9d89dc2eb061d548
> -- 
> 2.55.0
>