| Message ID | 5e1b119a51df19ead32561e87ce2ee1441b67154.1610364681.git.baruch@tkos.co.il (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | gpio: mvebu: Armada 8K/7K PWM support | expand |
Hi Baruch, this caught my eye: On Mon, Jan 11, 2021 at 12:47 PM Baruch Siach <baruch@tkos.co.il> wrote: > Update the example as well. Add the '#pwm-cells' and 'clocks' properties > for a complete working example. > > Reviewed-by: Rob Herring <robh@kernel.org> > Signed-off-by: Baruch Siach <baruch@tkos.co.il> (...) > +Optional properties: > + > +- marvell,pwm-offset: offset address of PWM duration control registers inside > + the syscon block (...) > ap_syscon: system-controller@6f4000 { > compatible = "syscon", "simple-mfd"; > @@ -101,6 +106,9 @@ ap_syscon: system-controller@6f4000 { > gpio-controller; > #gpio-cells = <2>; > gpio-ranges = <&ap_pinctrl 0 0 19>; > + marvell,pwm-offset = <0x10c0>; This seems to be one of those cases where we start to encode things related to the hardware variant into the device tree. Is this just documenting ABI that was introduced in the past and we can not do anything about now? In that case it is OK I suppose. For a new binding we would certainly require that the system controller provide a specific tertiary compatible string for this, lest we disguise the not-so-simple system controller as "simple-mfd" so: compatible = "syscon", "simple-mfd", "my-silicon-id"; Then detect the PWM offset by using if(of_device_is_compatibe(np, "my-silicon-id")) in the code rather than parsing any marvell,pwm-offset property. Yours, Linus Walleij
On Tue, Jan 12, 2021 at 09:49:16AM +0100, Linus Walleij wrote: > Hi Baruch, > > this caught my eye: > > On Mon, Jan 11, 2021 at 12:47 PM Baruch Siach <baruch@tkos.co.il> wrote: > > > Update the example as well. Add the '#pwm-cells' and 'clocks' properties > > for a complete working example. > > > > Reviewed-by: Rob Herring <robh@kernel.org> > > Signed-off-by: Baruch Siach <baruch@tkos.co.il> > > (...) > > +Optional properties: > > + > > +- marvell,pwm-offset: offset address of PWM duration control registers inside > > + the syscon block > (...) > > ap_syscon: system-controller@6f4000 { > > compatible = "syscon", "simple-mfd"; > > @@ -101,6 +106,9 @@ ap_syscon: system-controller@6f4000 { > > gpio-controller; > > #gpio-cells = <2>; > > gpio-ranges = <&ap_pinctrl 0 0 19>; > > + marvell,pwm-offset = <0x10c0>; > > This seems to be one of those cases where we start to encode things related > to the hardware variant into the device tree. > > Is this just documenting ABI that was introduced in the past and we can not > do anything about now? In that case it is OK I suppose. > > For a new binding we would certainly require that the system controller > provide a specific tertiary compatible string for this, lest we disguise > the not-so-simple system controller as "simple-mfd" so: > > compatible = "syscon", "simple-mfd", "my-silicon-id"; > > Then detect the PWM offset by using > if(of_device_is_compatibe(np, "my-silicon-id")) > in the code rather than parsing any marvell,pwm-offset property. I think it would be a good idea to describe the hardware more fully. For the CP110 and AP80x dies on Armada 8040: CP110 AP80x Offset Offset 00/40 5040 Data Out 04/44 5044 Data Out Enable 08/48 5048 Blink Enable 0c/4c 504c Data In polarity 10/50 5050 Data In 14/54 5054 IRQ Cause 18/58 5058 IRQ Mask 1c/5c 505c IRQ Level mask 20/60 5060 Blink Counter Select 28/68 5068 Control Set 2c/6c 506c Control Clear 30/70 5070 Data Out Set 34/74 5074 Data Out Clear f0 50c0 Blink Counter A ON duration f4 50c4 Blink Counter A OFF duration f8 50c8 Blink Counter B ON duration fc 50cc Blink Counter B OFF duration We identify both of these using a compatible of "marvell,armada-8k-gpio" which really only describes the first 64 bytes of the register set: ap_gpio: gpio@1040 { compatible = "marvell,armada-8k-gpio"; offset = <0x1040>; ... }; CP11X_LABEL(gpio1): gpio@100 { compatible = "marvell,armada-8k-gpio"; offset = <0x100>; ... }; CP11X_LABEL(gpio2): gpio@140 { compatible = "marvell,armada-8k-gpio"; offset = <0x140>; ... }; Note that on the CP11x dies, there are two GPIO controllers sharing the same set of blink counter registers - one at offset 0 the other at offset 0x40. However, the pwm-offset is the offset in the regmap of the parent node. It is possible to use a more specific compatible that would describe the PWM offset for the CP11x and AP806 (which would need two different ones) but that starts getting messy when you consider that we already describe an offset in regmap for the first 64 registers, and encoding the blink register offset in a compatible would partially end up encoding the "offset" we already have. In any case, these offsets are a function of how it was originally chosen to describe the hardware in DT, rather than anything about the hardware itself. The choice to use a syscon/regmap is purely an implementation decision rather than something from the hardware, so this DT description is already based around describing what is required for the Linux implementation, rather than purely being a hardware description.
On Tue, Jan 12, 2021 at 11:36 AM Russell King - ARM Linux admin <linux@armlinux.org.uk> wrote: > In any case, these offsets are a function of how it was originally > chosen to describe the hardware in DT, rather than anything about the > hardware itself. The choice to use a syscon/regmap is purely an > implementation decision rather than something from the hardware, so > this DT description is already based around describing what is required > for the Linux implementation, rather than purely being a hardware > description. OK I will not complain about it then, this kind of thing happens sometimes. Thanks Russell! Linus Walleij
diff --git a/Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt b/Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt index e31511255d8e..052a967c1f28 100644 --- a/Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt +++ b/Documentation/devicetree/bindings/arm/marvell/ap80x-system-controller.txt @@ -80,6 +80,11 @@ Required properties: - offset: offset address inside the syscon block +Optional properties: + +- marvell,pwm-offset: offset address of PWM duration control registers inside + the syscon block + Example: ap_syscon: system-controller@6f4000 { compatible = "syscon", "simple-mfd"; @@ -101,6 +106,9 @@ ap_syscon: system-controller@6f4000 { gpio-controller; #gpio-cells = <2>; gpio-ranges = <&ap_pinctrl 0 0 19>; + marvell,pwm-offset = <0x10c0>; + #pwm-cells = <2>; + clocks = <&ap_clk 3>; }; };