On 10/28/25 13:42, Maud Spierings wrote:

On 10/28/25 13:15, Matti Vaittinen wrote:

quoted

Hi Maud,

Thanks for the upstreaming work! :)

On 22/10/2025 10:22, Maud Spierings via B4 Relay wrote:

quoted

From: Maud Spierings <maudspierings@gocontroll.com>

The Ka-Ro Electronics tx8m-1610 is a COM based on the imx8mm SOC. It has
1 GB of ram and 4 GB of eMMC storage on board.

Add it to enable boards based on this module

Signed-off-by: Maud Spierings <maudspierings@gocontroll.com>
---
  .../arm64/boot/dts/freescale/imx8mm-tx8m-1610.dtsi | 439 ++++++++++ 
+ ++++++++++
  1 file changed, 439 insertions(+)

diff --git a/arch/arm64/boot/dts/freescale/imx8mm-tx8m-1610.dtsi b/ 

arch/arm64/boot/dts/freescale/imx8mm-tx8m-1610.dtsi
new file mode 100644
index 0000000000000..46d3ad80942cc

--- /dev/null
+++ b/arch/arm64/boot/dts/freescale/imx8mm-tx8m-1610.dtsi

@@ -0,0 +1,439 @@
+// SPDX-License-Identifier: (GPL-2.0 OR MIT)
+/*
+ * Copyright (C) 2021 Lothar Waßmann <LW@KARO-electronics.de>
+ * 2025 Maud Spierings <maudspierings@gocontroll.com>
+ */
+
+#include "imx8mm.dtsi"
+

// snip

quoted

+    pmic: pmic@4b {
+        compatible = "rohm,bd71847";
+        reg = <0x4b>;
+        interrupt-parent = <&gpio1>;
+        interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
+        pinctrl-0 = <&pinctrl_pmic>;
+        pinctrl-names = "default";
+        rohm,reset-snvs-powered;
+
+        regulators {
+            reg_vdd_soc: BUCK1 {
+                regulator-always-on;
+                regulator-boot-on;
+                regulator-max-microvolt = <900000>;
+                regulator-min-microvolt = <780000>;
+                regulator-name = "buck1";
+                regulator-ramp-delay = <1250>;
+            };
+
+            reg_vdd_arm: BUCK2 {
+                regulator-always-on;
+                regulator-boot-on;
+                regulator-max-microvolt = <950000>;
+                regulator-min-microvolt = <805000>;
+                regulator-name = "buck2";
+                regulator-ramp-delay = <1250>;
+                rohm,dvs-run-voltage = <950000>;
+                rohm,dvs-idle-voltage = <810000>;
+            };
+
+            reg_vdd_dram: BUCK3 {
+                regulator-always-on;
+                regulator-boot-on;
+                regulator-max-microvolt = <900000>;
+                regulator-min-microvolt = <805000>;
+                regulator-name = "buck3";
+            };
+
+            reg_vdd_3v3: BUCK4 {
+                regulator-always-on;
+                regulator-boot-on;
+                regulator-max-microvolt = <3300000>;
+                regulator-min-microvolt = <3300000>;
+                regulator-name = "buck4";
+            };
+
+            reg_vdd_1v8: BUCK5 {
+                regulator-always-on;
+                regulator-boot-on;
+                regulator-max-microvolt = <1950000>;
+                regulator-min-microvolt = <1700000>;
+                regulator-name = "buck5";
+            };
+
+            BUCK6 {
+                regulator-always-on;
+                regulator-boot-on;
+                /*
+                 * The default output voltage is 1.1V, bumped
+                 * to 1.35V in HW by a 499R/2.2K voltage divider in the
+                 * feedback path.
+                 */

Could/Should this be described using the:
'rohm,feedback-pull-up-r1-ohms' and
'rohm,feedback-pull-up-r2-ohms'? If I understand the comment 
correctly, that might allow the driver to be able to use correctly 
scaled voltages.

https://elixir.bootlin.com/linux/v6.18-rc1/source/Documentation/ 
devicetree/bindings/regulator/rohm,bd71837-regulator.yaml#L108

Ah I didn't know those existed, should've checked the bindings in more 
detail, thanks for the hint!

I will have to investigate this carefully, since I don't have access to 
the actual design of the COM, so I don't know exactly what is there.

So I am not yet entirely sure if this works out, I used the calculation 
in the driver:

/*
  * Setups where regulator (especially the buck8) output voltage is scaled
  * by adding external connection where some other regulator output is 
connected
  * to feedback-pin (over suitable resistors) is getting popular amongst 
users
  * of BD71837. (This allows for example scaling down the buck8 voltages 
to suit
  * lover GPU voltages for projects where buck8 is (ab)used to supply power
  * for GPU. Additionally some setups do allow DVS for buck8 but as this do
  * produce voltage spikes the HW must be evaluated to be able to 
survive this
  * - hence I keep the DVS disabled for non DVS bucks by default. I 
don't want
  * to help you burn your proto board)
  *
  * So we allow describing this external connection from DT and scale the
  * voltages accordingly. This is what the connection should look like:
  *
  * |------------|
  * |	buck 8  |-------+----->Vout
  * |		|	|
  * |------------|	|
  *	| FB pin	|
  *	|		|
  *	+-------+--R2---+
  *		|
  *		R1
  *		|
  *	V FB-pull-up
  *
  *	Here the buck output is sifted according to formula:
  *
  * Vout_o = Vo - (Vpu - Vo)*R2/R1
  * Linear_step = step_orig*(R1+R2)/R1
  *
  * where:
  * Vout_o is adjusted voltage output at vsel reg value 0
  * Vo is original voltage output at vsel reg value 0
  * Vpu is the pull-up voltage V FB-pull-up in the picture
  * R1 and R2 are resistor values.
  *
  * As a real world example for buck8 and a specific GPU:
  * VLDO = 1.6V (used as FB-pull-up)
  * R1 = 1000ohms
  * R2 = 150ohms
  * VSEL 0x0 => 0.8V – (VLDO – 0.8) * R2 / R1 = 0.68V
  * Linear Step = 10mV * (R1 + R2) / R1 = 11.5mV
  */

Because I do not know the pull up voltage, and I am not sure if it is a 
pull up.

So:
Vout_o = 1.35V
Vo = 1.1V
Vpu = unknown
R2 = 499 Ohm
R1 = 2200 Ohm
Gives:
Vpu = ~0V

And:
Vout_o = 1.35V
Vo = 1.1V
Vpu = unknown
R2 = 2200 Ohm
R1 = 499 Ohm
Gives:
Vpu = ~1.04V

I am not quite sure which resistor is R1 and which is R2 but having 
there be a pull down to 0V seems the most logical answer?

I am adding Lothar from Ka-Ro to the CC maybe he can shed some light on 
this setup.

Kind regards,
Maud