Hi All,
I haven't receive any feedback on this patch neither the v1 nor this v2.
Maybe an issue with the mail. Add u.kleine-koenig@xxxxxxxxxxxx and hope to
have a feedback on this patch.
Best regards,
Hervé
On Wed, 8 Jan 2025 17:18:53 +0100
Herve Codina <herve.codina@xxxxxxxxxxx> wrote:
> Platforms can have a standardized connector/expansion slot that exposes
> signals like PWMs to expansion boards in an SoC agnostic way.
>
> The support for nexus node [1] has been added to handle those cases in
> commit bd6f2fd5a1d5 ("of: Support parsing phandle argument lists through
> a nexus node"). This commit introduced of_parse_phandle_with_args_map()
> to handle nexus nodes in a generic way and the gpio subsystem adopted
> the support in commit c11e6f0f04db ("gpio: Support gpio nexus dt
> bindings").
>
> A nexus node allows to remap a phandle list in a consumer node through a
> connector node in a generic way. With this remapping supported, the
> consumer node needs to knwow only about the nexus node. Resources behind
> the nexus node are decoupled by the nexus node itself.
>
> This is particularly useful when this consumer is described in a
> device-tree overlay. Indeed, to have the exact same overlay reused with
> several base systems the overlay needs to known only about the connector
> is going to be applied to without any knowledge of the SoC (or the
> component providing the resource) available in the system.
>
> As an example, suppose 3 PWMs connected to a connector. The connector
> PWM 0 and 2 comes from the PWM 1 and 3 of the pwm-controller1. The
> connector PWM 1 comes from the PWM 4 of the pwm-controller2. An
> expansion device is connected to the connector and uses the connector
> PMW 1.
>
> Nexus node support in PWM allows the following description:
> soc {
> soc_pwm1: pwm-controller1 {
> #pwm-cells = <3>;
> };
>
> soc_pwm2: pwm-controller2 {
> #pwm-cells = <3>;
> };
> };
>
> connector: connector {
> #pwm-cells = <3>;
> pwm-map = <0 0 0 &soc_pwm1 1 0 0>,
> <1 0 0 &soc_pwm2 4 0 0>,
> <2 0 0 &soc_pwm1 3 0 0>,
> pwm-map-mask = <0xffffffff 0x0 0x0>;
> pwm-map-pass-thru = <0x0 0xffffffff 0xffffffff>
> };
>
> expansion_device {
> pwms = <&connector 1 57000 0>;
> };
>
> From the expansion device point of view, the PWM requested is the PWM 1
> available at the connector regardless of the exact PWM wired to this
> connector PWM 1. Thanks to nexus node remapping described at connector
> node, this PWM is the PWM 4 of the pwm-controller2.
>
> The nexus node remapping handling consists in handling #*-cells, *-map,
> *-map-mask and *-map-pass-thru properties. This is already supported
> by of_parse_phandle_with_args_map().
>
> Add support for nexus node device-tree binding and the related remapping
> in the PWM subsystem by simply using of_parse_phandle_with_args_map()
> instead of of_parse_phandle_with_args().
>
> [1] https://github.com/devicetree-org/devicetree-specification/blob/v0.4/source/chapter2-devicetree-basics.rst#nexus-nodes-and-specifier-mapping
>
> Signed-off-by: Herve Codina <herve.codina@xxxxxxxxxxx>
> ---
> Changes v1 -> v2
> - Rework commit log
>
> drivers/pwm/core.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/pwm/core.c b/drivers/pwm/core.c
> index 9c733877e98e..4a7454841cef 100644
> --- a/drivers/pwm/core.c
> +++ b/drivers/pwm/core.c
> @@ -1707,8 +1707,7 @@ static struct pwm_device *of_pwm_get(struct device *dev, struct device_node *np,
> return ERR_PTR(index);
> }
>
> - err = of_parse_phandle_with_args(np, "pwms", "#pwm-cells", index,
> - &args);
> + err = of_parse_phandle_with_args_map(np, "pwms", "pwm", index, &args);
> if (err) {
> pr_err("%s(): can't parse \"pwms\" property\n", __func__);
> return ERR_PTR(err);
