[RFC] rpi: add support to enable usb power domain

[Stephen Warren]

On 10/28/2015 02:40 PM, Alexander Aring wrote:
> This patch adds support for RPi several Power Domains and enable support
> to enable the USB Power Domain when it's not enabled before.
> 
> This patch based on Eric Anholt's patch to support Power Domains. He had
> an issue about -EPROBE_DEFER inside the power domain subsystem, this
> issue was solved by commit <311fa6a> ("PM / Domains: Return -EPROBE_DEFER
> if we fail to init or turn-on domain").

> diff --git a/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.txt b/Documentation/devicetree/bindings/arm/bcm/raspberrypi,bcm2835-firmware.txt

>  firmware {
>  	compatible = "raspberrypi,bcm2835-firmware";
>  	mboxes = <&mailbox>;
> +	#power-domain-cells = <1>;
> +};

I would have expected a separate DT node for the power domains driver
that referenced the firmware node by phandle. I believe that's why the
firmware node exports mailboxes to other drivers. If the firmware driver
was going to implement all the features directly, it wouldn't need to
act as a mailbox provider, since all the mailbox programming would be
internal.

> diff --git a/drivers/firmware/raspberrypi.c b/drivers/firmware/raspberrypi.c

> +#define RPI_POWER_DOMAIN(_domain, _name)			\
> +	[_domain] =						\
> +	{							\

I'd expect { wrapped onto the previous line.

> +static int raspberrypi_firmware_set_power(struct rpi_firmware *fw,
> +					  u32 domain, bool on)

> +	packet.on = on;
> +	ret = rpi_firmware_property(fw, RPI_FIRMWARE_SET_POWER_STATE, &packet,
> +				    sizeof(packet));
> +	if (!ret && !packet.on)
> +		ret = -EINVAL;

The error is only reported for power off requests?

> +/* Asks the firmware to if power is on for a specific power domain. */
> +static int raspberrypi_firmware_power_is_on(struct rpi_firmware *fw,
> +					    u32 domain)

> +	packet.domain = domain;
> +	ret = rpi_firmware_property(fw, RPI_FIRMWARE_GET_POWER_STATE, &packet,
> +				    sizeof(packet));
> +	if (ret < 0)
> +		return ret;

Hmm. If rpi_firmware_property() returns <0 on error, I'm confused what
the test I commented on above is intended to do.

> +/*
> + * IMPORTANT: be sure this array has no entries which are not specified
> + * between others by RPI_POWER_DOMAIN, otherwise mapping between
> + * generic_pm_domain array doesn't work anymore.
> + */

"has no entries which are not specified between others by
RPI_POWER_DOMAIN" might be better phrased as "is contiguous" or
"contains only contiguous entries".

> @@ -208,15 +312,44 @@ static int rpi_firmware_probe(struct platform_device *pdev)

> +	for (i = 0; i < num_domains; i++) {
> +		bool is_off;
> +
> +		rpi_power_domains[i].fw = fw;
> +		power_domains[i] = &rpi_power_domains[i].base;
> +
> +		/* get the initial state */
> +		ret = raspberrypi_firmware_power_is_on(fw, i);
> +		if (ret < 0)
> +			goto mbox;

The label name "mbox" doesn't give a clue that it's an error handler.
"free_mbox" might be better.

> +mbox:
> +	mbox_free_channel(fw->chan);
> +	return ret;
>  }

Does the pm_genpd_init() call for all the power domains need to be
undone at all?