| Message ID | 20241012025603.1644451-2-florian.fainelli@broadcom.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | pwm: brcmstb: Support configurable open-drain mode | expand |
On Fri, Oct 11, 2024 at 07:56:02PM -0700, Florian Fainelli wrote: > Document the 'open-drain' property that allows configuring the PWM > controller outputs in open drain versus totem pole. > > Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> > --- > Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml > index 119de3d7f9dd..12851c43a612 100644 > --- a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml > +++ b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml > @@ -25,6 +25,12 @@ properties: > clocks: > maxItems: 1 > > + open-drain: > + type: boolean > + description: > + Configure the outputs with open-drain structure, if omitted totem pole > + structure is used. > + There's one other PWM with 'open-drain' so move the definition to pwm.yaml. Alternatively, 'drive-open-drain' is a much more commonly used variation. Another thing to consider is for any PWM controller with more than 1 output, you might want this to be per output and therefore should be a flag in the cells. Rob
On 10/15/24 09:32, Rob Herring wrote: > On Fri, Oct 11, 2024 at 07:56:02PM -0700, Florian Fainelli wrote: >> Document the 'open-drain' property that allows configuring the PWM >> controller outputs in open drain versus totem pole. >> >> Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> >> --- >> Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml | 6 ++++++ >> 1 file changed, 6 insertions(+) >> >> diff --git a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml >> index 119de3d7f9dd..12851c43a612 100644 >> --- a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml >> +++ b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml >> @@ -25,6 +25,12 @@ properties: >> clocks: >> maxItems: 1 >> >> + open-drain: >> + type: boolean >> + description: >> + Configure the outputs with open-drain structure, if omitted totem pole >> + structure is used. >> + > > There's one other PWM with 'open-drain' so move the definition to > pwm.yaml. Ah indeed, there is one now, great. > > Alternatively, 'drive-open-drain' is a much more commonly used > variation. That name works just as well. > > Another thing to consider is for any PWM controller with more than > 1 output, you might want this to be per output and therefore should be > a flag in the cells. Yes, that is a good point, this controller has two channels, so it seems like increasing the #pwm-cells might be the way to go. Thanks!
Hello, On Tue, Oct 15, 2024 at 10:07:10AM -0700, Florian Fainelli wrote: > On 10/15/24 09:32, Rob Herring wrote: > > Another thing to consider is for any PWM controller with more than > > 1 output, you might want this to be per output and therefore should be > > a flag in the cells. > > Yes, that is a good point, this controller has two channels, so it seems > like increasing the #pwm-cells might be the way to go. So the idea is something like: diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h index ab9a077e3c7d..d18b006a7399 100644 --- a/include/dt-bindings/pwm/pwm.h +++ b/include/dt-bindings/pwm/pwm.h @@ -11,5 +11,6 @@ #define _DT_BINDINGS_PWM_PWM_H #define PWM_POLARITY_INVERTED (1 << 0) +#define PWM_OUTPUT_OPEN_DRAIN (1 << 1) #endif and then add support for that to the core and drivers? There is some intersection with pinctrl (depending on hardware). I wonder if abstracting this somehow using the typical pinctrl properties would be a saner option?? Best regards Uwe
On 10/29/24 03:44, Uwe Kleine-König wrote: > Hello, > > On Tue, Oct 15, 2024 at 10:07:10AM -0700, Florian Fainelli wrote: >> On 10/15/24 09:32, Rob Herring wrote: >>> Another thing to consider is for any PWM controller with more than >>> 1 output, you might want this to be per output and therefore should be >>> a flag in the cells. >> >> Yes, that is a good point, this controller has two channels, so it seems >> like increasing the #pwm-cells might be the way to go. > > So the idea is something like: > > diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h > index ab9a077e3c7d..d18b006a7399 100644 > --- a/include/dt-bindings/pwm/pwm.h > +++ b/include/dt-bindings/pwm/pwm.h > @@ -11,5 +11,6 @@ > #define _DT_BINDINGS_PWM_PWM_H > > #define PWM_POLARITY_INVERTED (1 << 0) > +#define PWM_OUTPUT_OPEN_DRAIN (1 << 1) > > #endif > > and then add support for that to the core and drivers? There is some > intersection with pinctrl (depending on hardware). I wonder if > abstracting this somehow using the typical pinctrl properties would be a > saner option?? But what if the pin is not managed by a pinctrl provider? I have started going the route of implementing the PWM_OUTPUT_OPEN_DRAIN bit as an additional specifier in the #pwm-cells, but I am not sure to what extent this should be allowed to be changed at runtime.
Hello Florian, [adding Linus and linux-gpio to Cc:] On Tue, Oct 29, 2024 at 09:03:57AM -0700, Florian Fainelli wrote: > On 10/29/24 03:44, Uwe Kleine-König wrote: > > On Tue, Oct 15, 2024 at 10:07:10AM -0700, Florian Fainelli wrote: > > > On 10/15/24 09:32, Rob Herring wrote: > > > > Another thing to consider is for any PWM controller with more than > > > > 1 output, you might want this to be per output and therefore should be > > > > a flag in the cells. > > > > > > Yes, that is a good point, this controller has two channels, so it seems > > > like increasing the #pwm-cells might be the way to go. > > > > So the idea is something like: > > > > diff --git a/include/dt-bindings/pwm/pwm.h b/include/dt-bindings/pwm/pwm.h > > index ab9a077e3c7d..d18b006a7399 100644 > > --- a/include/dt-bindings/pwm/pwm.h > > +++ b/include/dt-bindings/pwm/pwm.h > > @@ -11,5 +11,6 @@ > > #define _DT_BINDINGS_PWM_PWM_H > > #define PWM_POLARITY_INVERTED (1 << 0) > > +#define PWM_OUTPUT_OPEN_DRAIN (1 << 1) > > #endif > > > > and then add support for that to the core and drivers? There is some > > intersection with pinctrl (depending on hardware). I wonder if > > abstracting this somehow using the typical pinctrl properties would be a > > saner option?? > > But what if the pin is not managed by a pinctrl provider? Then create one? If that's the PWM itself that is the pinctrl device it would look as follows: pwm@f0408000 { compatible = "brcm,bcm7038-pwm"; pinctrl-0 = <&pwm_pins>; reg = <0xf0408000 0x28>; #pwm-cells = <2>; #pinctrl-cells = <0>; clocks = <&upg_fixed>; pinctrl { pwm_pins: pwm-pins { pins = "A", "B"; drive-open-drain; }; }; }; Maybe this is difficult if there is a pinctrl that configures the output as "PWM" and then there is that additional register in the PWM IP to make this pin open drain? One could just use pinctrl-0 = <&pwm_pins>, <&system_pinctrl_pwm>; then. Not entirely sure this is overengineered, but the dt representation would be nice (IMHO). Thoughts? > I have started > going the route of implementing the PWM_OUTPUT_OPEN_DRAIN bit as an > additional specifier in the #pwm-cells, but I am not sure to what extent > this should be allowed to be changed at runtime. I would not expect that the open-drainness needs to change at runtime. Best regards Uwe
diff --git a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml index 119de3d7f9dd..12851c43a612 100644 --- a/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml +++ b/Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml @@ -25,6 +25,12 @@ properties: clocks: maxItems: 1 + open-drain: + type: boolean + description: + Configure the outputs with open-drain structure, if omitted totem pole + structure is used. + required: - compatible - reg
Document the 'open-drain' property that allows configuring the PWM controller outputs in open drain versus totem pole. Signed-off-by: Florian Fainelli <florian.fainelli@broadcom.com> --- Documentation/devicetree/bindings/pwm/brcm,bcm7038-pwm.yaml | 6 ++++++ 1 file changed, 6 insertions(+)