Re: [RFC PATCH 1/1] pinctrl: rockchip: add support for per-pinmux io-domain dependency

Michael Riesch
2022-08-11T07:54:42Z

Hi Quentin,

Thank you for your efforts! This will solve several issues that are
bound to pop up if a board deviates from the Rockchip reference design.
It seems this does not happen very often, though, which would explain
the lack of responses to your initial query... :-/

A few comments inline:

On 8/2/22 11:52, Quentin Schulz wrote:
> From: Quentin Schulz <quentin.schulz@theobroma-systems.com>
>
> On some Rockchip SoCs, some SoC pins are split in what are called IO
> domains.
>
> An IO domain is supplied power externally, by regulators from a PMIC for
> example. This external power supply is then used by the IO domain as
> "supply" for the IO pins if they are outputs.
>
> Each IO domain can configure which voltage the IO pins will be operating
> on (1.8V or 3.3V).

Just for the sake of completeness: 2.5V is possibly as well (at least on
RK356x), right?

> There already exists an IO domain driver for Rockchip SoCs[1]. This
> driver allows to explicit the relationship between the external power

...allows to model explicitly...?

> supplies and IO domains[2]. This makes sure the regulators are enabled
> by the Linux kernel so the IO domains are supplied with power and
> correctly configured as per the supplied voltage.
> This driver is a regulator consumer and does not offer any other
> interface for device dependency.
>
> However, IO pins belonging to an IO domain need to have this IO domain
> correctly configured before they are being used otherwise they do not
> operate correctly (in our case, a pin configured as output clock was
> oscillating between 0 and 150mV instead of the expected 1V8).
>
> In order to make this dependency transparent to the consumer of those
> pins and not add Rockchip-specific code to third party drivers (a camera
> driver in our case), it is hooked into the pinctrl driver which is
> Rockchip-specific obviously.

This approach seems reasonable. But just for my understanding: Does this
mean we need to edit e.g. rk3568-pinctrl.dtsi, iterate over all entries,
and add rockchip,iodomains = <&corresponding_io_domain>;?

If not, at which place are the rockchip,iodomains properties inserted?

> [1] drivers/soc/rockchip/io-domain.c
> [2] Documentation/devicetree/bindings/power/rockchip-io-domain.yaml
>
> Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
> ---
> drivers/pinctrl/pinctrl-rockchip.c | 19 +++++++++++++++++++
> drivers/pinctrl/pinctrl-rockchip.h | 1 +
> 2 files changed, 20 insertions(+)
>
> diff --git a/drivers/pinctrl/pinctrl-rockchip.c b/drivers/pinctrl/pinctrl-rockchip.c
> index 32e41395fc76..c3c2801237b5 100644
> --- a/drivers/pinctrl/pinctrl-rockchip.c
> +++ b/drivers/pinctrl/pinctrl-rockchip.c
> @@ -24,6 +24,8 @@
> #include <linux/of_address.h>
> #include <linux/of_device.h>
> #include <linux/of_irq.h>
> +#include <linux/of_platform.h>
> +#include <linux/platform_device.h>
> #include <linux/pinctrl/machine.h>
> #include <linux/pinctrl/pinconf.h>
> #include <linux/pinctrl/pinctrl.h>
> @@ -2370,6 +2372,12 @@ static int rockchip_pmx_set(struct pinctrl_dev *pctldev, unsigned selector,
> dev_dbg(dev, "enable function %s group %s\n",
> info->functions[selector].name, info->groups[group].name);
>
> + if (info->groups[group].io_domain &&
> + !platform_get_drvdata(info->groups[group].io_domain)) {
> + dev_err(info->dev, "IO domain device is required but not probed yet, deferring...");

Probably this has been left in there for debugging, but should be
removed to avoid spamming dmesg. IIUC this condition could occur several
times.

> + return -EPROBE_DEFER;
> + }
> +
> /*
> * for each pin in the pin group selected, program the corresponding
> * pin function number in the config register.
> @@ -2663,6 +2671,7 @@ static int rockchip_pinctrl_parse_groups(struct device_node *np,
> {
> struct device *dev = info->dev;
> struct rockchip_pin_bank *bank;
> + struct device_node *node;
> int size;
> const __be32 *list;
> int num;
> @@ -2684,6 +2693,16 @@ static int rockchip_pinctrl_parse_groups(struct device_node *np,
> if (!size || size % 4)
> return dev_err_probe(dev, -EINVAL, "wrong pins number or pins and configs should be by 4\n");
>
> + node = of_parse_phandle(np, "rockchip,io-domains", 0);
> + if (node) {
> + grp->io_domain = of_find_device_by_node(node);
> + of_node_put(node);
> + if (!grp->io_domain) {
> + dev_err(info->dev, "couldn't find IO domain device\n");
> + return -ENODEV;

Again just for my understanding: The property is optional in order to
provide compatibility with older device trees, right?

> + }
> + }
> +
> grp->npins = size / 4;
>
> grp->pins = devm_kcalloc(dev, grp->npins, sizeof(*grp->pins), GFP_KERNEL);
> diff --git a/drivers/pinctrl/pinctrl-rockchip.h b/drivers/pinctrl/pinctrl-rockchip.h
> index ec46f8815ac9..56bc008eb7df 100644
> --- a/drivers/pinctrl/pinctrl-rockchip.h
> +++ b/drivers/pinctrl/pinctrl-rockchip.h
> @@ -434,6 +434,7 @@ struct rockchip_pin_group {
> unsigned int npins;
> unsigned int *pins;
> struct rockchip_pin_config *data;
> + struct platform_device *io_domain;
> };
>
> /**

Looking forward to the v1 of this series, which I'd be happy to test.

Best regards,
Michael