[PATCH] arm64: dts: imx8mn-var-som-symphony: add vcc supply for PCA9534

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The following warning is shown when probing device:

    pca953x 1-0020: supply vcc not found, using dummy regulator

Add fixed 3.3v regulator as vcc supply to silence the warning.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
---
 arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts b/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts
index a7a57442cb81..583b9859df3a 100644
--- a/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts
+++ b/arch/arm64/boot/dts/freescale/imx8mn-var-som-symphony.dts

@@ -79,6 +79,7 @@ pca9534: gpio@20 {
 		interrupts = <7 IRQ_TYPE_EDGE_FALLING>;
 		#gpio-cells = <2>;
 		wakeup-source;
+		vcc-supply = <&reg_3v3_fixed>;
 
 		/* USB 3.0 OTG (usbotg1) / SATA port switch, set to USB 3.0 */
 		usb3-sata-sel-hog {

base-commit: d2f51b3516dade79269ff45eae2a7668ae711b25
-- 
2.39.2

On 06/11/2023 19:57, Hugo Villeneuve wrote:

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The following warning is shown when probing device:

    pca953x 1-0020: supply vcc not found, using dummy regulator

Add fixed 3.3v regulator as vcc supply to silence the warning.

This is not really a warning. It's perfectly fine to use dummy
regulator. Adding such fixed supply has sense in following cases:
1. Bindings require the supply,
2. This is in fact exactly that supply (verified on schematics).

Best regards,
Krzysztof

On Mon, 6 Nov 2023 21:39:42 +0100
Krzysztof Kozlowski [off-list ref] wrote:

On 06/11/2023 19:57, Hugo Villeneuve wrote:

quoted

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The following warning is shown when probing device:

    pca953x 1-0020: supply vcc not found, using dummy regulator

Add fixed 3.3v regulator as vcc supply to silence the warning.

This is not really a warning. It's perfectly fine to use dummy
regulator. Adding such fixed supply has sense in following cases:
1. Bindings require the supply,
2. This is in fact exactly that supply (verified on schematics).

Best regards,
Krzysztof

Hi Krzysztof,
this is case #2, but looking more closely at the carrier board
(symphony) schematics, it is not exactly the "reg_3v3_fixed" supply I
mentioned in the patch, as "reg_3v3_fixed" is located on the SOM and
only powers SOM components.

However, "reg_3v3_fixed", which is an always-on regulator (no software
enable control), is used as the enable input to a mosfet switch (Q2) on
the carrier board to generate the 3.3V (label BASE_PER_3V3 on the
schematics) used by all peripherals on that carrier board.

I guess I could then define a new "always-on" regulator labeled as,
for example, base_per_3v3, and then assign the pca953x vcc-supply
property to it?

Hugo.

On 06/11/2023 22:36, Hugo Villeneuve wrote:

On Mon, 6 Nov 2023 21:39:42 +0100
Krzysztof Kozlowski [off-list ref] wrote:

quoted

On 06/11/2023 19:57, Hugo Villeneuve wrote:

quoted

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The following warning is shown when probing device:

    pca953x 1-0020: supply vcc not found, using dummy regulator

Add fixed 3.3v regulator as vcc supply to silence the warning.

This is not really a warning. It's perfectly fine to use dummy
regulator. Adding such fixed supply has sense in following cases:
1. Bindings require the supply,
2. This is in fact exactly that supply (verified on schematics).

Best regards,
Krzysztof

Hi Krzysztof,
this is case #2, but looking more closely at the carrier board
(symphony) schematics, it is not exactly the "reg_3v3_fixed" supply I
mentioned in the patch, as "reg_3v3_fixed" is located on the SOM and
only powers SOM components.

However, "reg_3v3_fixed", which is an always-on regulator (no software
enable control), is used as the enable input to a mosfet switch (Q2) on
the carrier board to generate the 3.3V (label BASE_PER_3V3 on the
schematics) used by all peripherals on that carrier board.

I guess I could then define a new "always-on" regulator labeled as,
for example, base_per_3v3, and then assign the pca953x vcc-supply
property to it?

I guess this could be the same supply, even if this is not 100% true.
However it would be good if you put above explanation in the commit msg.

Best regards,
Krzysztof

On Tue, 7 Nov 2023 08:14:03 +0100
Krzysztof Kozlowski [off-list ref] wrote:

On 06/11/2023 22:36, Hugo Villeneuve wrote:

quoted

On Mon, 6 Nov 2023 21:39:42 +0100
Krzysztof Kozlowski [off-list ref] wrote:

quoted

On 06/11/2023 19:57, Hugo Villeneuve wrote:

quoted

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

The following warning is shown when probing device:

    pca953x 1-0020: supply vcc not found, using dummy regulator

Add fixed 3.3v regulator as vcc supply to silence the warning.

This is not really a warning. It's perfectly fine to use dummy
regulator. Adding such fixed supply has sense in following cases:
1. Bindings require the supply,
2. This is in fact exactly that supply (verified on schematics).

Best regards,
Krzysztof

Hi Krzysztof,
this is case #2, but looking more closely at the carrier board
(symphony) schematics, it is not exactly the "reg_3v3_fixed" supply I
mentioned in the patch, as "reg_3v3_fixed" is located on the SOM and
only powers SOM components.

However, "reg_3v3_fixed", which is an always-on regulator (no software
enable control), is used as the enable input to a mosfet switch (Q2) on
the carrier board to generate the 3.3V (label BASE_PER_3V3 on the
schematics) used by all peripherals on that carrier board.

I guess I could then define a new "always-on" regulator labeled as,
for example, base_per_3v3, and then assign the pca953x vcc-supply
property to it?

I guess this could be the same supply, even if this is not 100% true.
However it would be good if you put above explanation in the commit msg.

Hi,
I prefer to add a new supply, and with a proper label it will be more
self-documenting, and I will still add part of this explanation to the
updated commit message.

Thank you,
Hugo.