| Message ID | 20231106185736.668966-1-hugo@hugovil.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | arm64: dts: imx8mn-var-som-symphony: add vcc supply for PCA9534 | expand |
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 <krzysztof.kozlowski@linaro.org> wrote: > 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 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 <krzysztof.kozlowski@linaro.org> wrote: > >> 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 > > 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 <krzysztof.kozlowski@linaro.org> wrote: > On 06/11/2023 22:36, Hugo Villeneuve wrote: > > On Mon, 6 Nov 2023 21:39:42 +0100 > > Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote: > > > >> 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 > > > > 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.
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 = <®_3v3_fixed>; /* USB 3.0 OTG (usbotg1) / SATA port switch, set to USB 3.0 */ usb3-sata-sel-hog {