Re: [PATCH v2 2/3] usb: misc: onboard_usb_hub: Add reset-gpio support

[Matthias Kaehlcke <mka@chromium.org>]

On Fri, Jul 15, 2022 at 09:32:59AM +0200, Alexander Stein wrote:
> Despite default reset upon probe, release reset line after powering up
> the hub and assert reset again before powering down.
> 
> Signed-off-by: Alexander Stein <alexander.stein@ew.tq-group.com>
> ---
> Changes in v2:
> * Use device specific sleep times, if present
> * Use fsleep instead of usleep_range
> 
>  drivers/usb/misc/onboard_usb_hub.c | 29 +++++++++++++++++++++++++++++
>  drivers/usb/misc/onboard_usb_hub.h |  5 +++++
>  2 files changed, 34 insertions(+)
> 
> diff --git a/drivers/usb/misc/onboard_usb_hub.c b/drivers/usb/misc/onboard_usb_hub.c
> index 6b9b949d17d3..1dd7f4767def 100644
> --- a/drivers/usb/misc/onboard_usb_hub.c
> +++ b/drivers/usb/misc/onboard_usb_hub.c
> @@ -7,6 +7,7 @@
>  
>  #include <linux/device.h>
>  #include <linux/export.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/init.h>
>  #include <linux/kernel.h>
>  #include <linux/list.h>
> @@ -38,6 +39,8 @@ struct usbdev_node {
>  struct onboard_hub {
>  	struct regulator *vdd;
>  	struct device *dev;
> +	const struct onboard_hub_devtype_data *devtype_data;

This kind of device specific data is often call platform data, let's
call the struct 'onboard_hub_pdata' and the field 'pdata'?

> +	struct gpio_desc *reset_gpio;
>  	bool always_powered_in_suspend;
>  	bool is_powered_on;
>  	bool going_away;
> @@ -56,6 +59,11 @@ static int onboard_hub_power_on(struct onboard_hub *hub)
>  		return err;
>  	}
>  
> +	if (hub->devtype_data)

Instead of these checks let's make sure all hubs have pdata. Actually your
onboard_hub_probe() already esnures that the field is assigned.

> +		fsleep(hub->devtype_data->power_stable_time);
> +	if (hub->reset_gpio)
> +		gpiod_set_value_cansleep(hub->reset_gpio, 0);

I would have expected:

  	if (hub->reset_gpio) {
		fsleep(hub->devtype_data->power_stable_time);
		gpiod_set_value_cansleep(hub->reset_gpio, 0);
	}

For the TUSB8041 the 'power_stable_time' (td2 in the datasheet) is "VDD and
VDD33 stable before de-assertion of GRSTz", so no delay without reset.

> +
>  	hub->is_powered_on = true;
>  
>  	return 0;
> @@ -65,6 +73,12 @@ static int onboard_hub_power_off(struct onboard_hub *hub)
>  {
>  	int err;
>  
> +	if (hub->reset_gpio) {
> +		gpiod_set_value_cansleep(hub->reset_gpio, 1);
> +		if (hub->devtype_data)
> +			fsleep(hub->devtype_data->reset_duration);
> +	}
> +
>  	err = regulator_disable(hub->vdd);
>  	if (err) {
>  		dev_err(hub->dev, "failed to disable regulator: %d\n", err);
> @@ -219,6 +233,7 @@ static void onboard_hub_attach_usb_driver(struct work_struct *work)
>  
>  static int onboard_hub_probe(struct platform_device *pdev)
>  {
> +	const struct of_device_id *of_id;
>  	struct device *dev = &pdev->dev;
>  	struct onboard_hub *hub;
>  	int err;
> @@ -227,10 +242,24 @@ static int onboard_hub_probe(struct platform_device *pdev)
>  	if (!hub)
>  		return -ENOMEM;
>  
> +	of_id = of_match_device(onboard_hub_match, &pdev->dev);
> +	if (of_id)
> +		hub->devtype_data = of_id->data;
> +	else
> +		return -ENODEV;

Please change to:

	if (!of_id)
		return -ENODEV;

	hub->pdata = of_id->data;

With the currently supported Realtek hubs will fail to probe. Please add a pdata for
the RTS541x hubs. The have no reset signal, so the values can be 0.

> +
>  	hub->vdd = devm_regulator_get(dev, "vdd");
>  	if (IS_ERR(hub->vdd))
>  		return PTR_ERR(hub->vdd);
>  
> +	hub->reset_gpio = devm_gpiod_get_optional(dev, "reset",
> +						  GPIOD_OUT_HIGH);
> +	if (IS_ERR(hub->reset_gpio))
> +		return dev_err_probe(dev, PTR_ERR(hub->reset_gpio), "failed to get reset GPIO\n");
> +
> +	if (hub->devtype_data && hub->reset_gpio)

drop check 'hub->devtype_data' check

> +		fsleep(hub->devtype_data->reset_duration);
> +
>  	hub->dev = dev;
>  	mutex_init(&hub->lock);
>  	INIT_LIST_HEAD(&hub->udev_list);
> diff --git a/drivers/usb/misc/onboard_usb_hub.h b/drivers/usb/misc/onboard_usb_hub.h
> index d3a5b6938582..7e743f4c8aaa 100644
> --- a/drivers/usb/misc/onboard_usb_hub.h
> +++ b/drivers/usb/misc/onboard_usb_hub.h
> @@ -6,6 +6,11 @@
>  #ifndef _USB_MISC_ONBOARD_USB_HUB_H
>  #define _USB_MISC_ONBOARD_USB_HUB_H
>  
> +struct onboard_hub_devtype_data {
> +	unsigned long power_stable_time;	/* power stabilization time in us */
> +	unsigned long reset_duration;		/* reset pulse width in us */

Let's encode the unit in the field name:

	unsigned long power_stable_us;
	unsigned long reset_us;

> +};

Is it necessary to define this struct in onboard_usb_hub.h? It seems it
could as well be defined in onboard_usb_hub.c.