Re: [PATCH v3] usb: renesas_usbhs: Allow an OTG PHY driver to provide VBUS

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Phil,

Thank you for the patch.

On Thursday 02 July 2015 11:26:33 Phil Edworthy wrote:
> These changes allow a PHY driver to trigger a VBUS interrupt and
> to provide the value of VBUS.
> 
> Signed-off-by: Phil Edworthy <phil.edworthy@renesas.com>
> 
> ---
> v3:
>   - Changed how indirect vbus is plumbed in.
>   - Removed unnecessary (void) on call to otg_set_peripheral.
>   - Moved code that connects to bus through transceiver so it
>     is before setting gpriv->driver.
> 
> v2:
>   - vbus variables changed from int to bool.
>   - dev_info() changed to dev_err()
> ---
>  drivers/usb/renesas_usbhs/common.c     |  8 +++++--
>  drivers/usb/renesas_usbhs/common.h     |  2 ++
>  drivers/usb/renesas_usbhs/mod_gadget.c | 38 +++++++++++++++++++++++++++++++
>  3 files changed, 46 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/renesas_usbhs/common.c
> b/drivers/usb/renesas_usbhs/common.c index 0f7e850..15e67d8 100644
> --- a/drivers/usb/renesas_usbhs/common.c
> +++ b/drivers/usb/renesas_usbhs/common.c
> @@ -379,7 +379,10 @@ static void usbhsc_hotplug(struct usbhs_priv *priv)
>  	/*
>  	 * get vbus status from platform
>  	 */
> -	enable = usbhs_platform_call(priv, get_vbus, pdev);
> +	if (priv->vbus_is_indirect)
> +		enable = priv->vbus_indirect_value;
> +	else
> +		enable = usbhs_platform_call(priv, get_vbus, pdev);
> 
>  	/*
>  	 * get id from platform
> @@ -662,7 +665,8 @@ static int usbhs_probe(struct platform_device *pdev)
>  	pm_runtime_enable(&pdev->dev);
>  	if (!usbhsc_flags_has(priv, USBHSF_RUNTIME_PWCTRL)) {
>  		usbhsc_power_ctrl(priv, 1);
> -		usbhs_mod_autonomy_mode(priv);
> +		if (!priv->vbus_is_indirect)

Isn't this racy ? The vbus_session operation is called by transceivers from 
interrupt handlers or work queues. Do we have a guarantee that it will be 
called at least once before this code is reached ? Please see below for a 
possible way to fix this.

> +			usbhs_mod_autonomy_mode(priv);
>  	}
> 
>  	/*
> diff --git a/drivers/usb/renesas_usbhs/common.h
> b/drivers/usb/renesas_usbhs/common.h index 8c5fc12..478700c 100644
> --- a/drivers/usb/renesas_usbhs/common.h
> +++ b/drivers/usb/renesas_usbhs/common.h
> @@ -255,6 +255,8 @@ struct usbhs_priv {
>  	struct renesas_usbhs_driver_param	dparam;
> 
>  	struct delayed_work notify_hotplug_work;
> +	bool vbus_is_indirect;
> +	bool vbus_indirect_value;
>  	struct platform_device *pdev;
> 
>  	struct extcon_dev *edev;
> diff --git a/drivers/usb/renesas_usbhs/mod_gadget.c
> b/drivers/usb/renesas_usbhs/mod_gadget.c index dc2aa32..93ad4ea 100644
> --- a/drivers/usb/renesas_usbhs/mod_gadget.c
> +++ b/drivers/usb/renesas_usbhs/mod_gadget.c
> @@ -21,6 +21,7 @@
>  #include <linux/platform_device.h>
>  #include <linux/usb/ch9.h>
>  #include <linux/usb/gadget.h>
> +#include <linux/usb/otg.h>
>  #include "common.h"
> 
>  /*
> @@ -50,6 +51,7 @@ struct usbhsg_gpriv {
>  	int			 uep_size;
> 
>  	struct usb_gadget_driver	*driver;
> +	struct usb_phy		*transceiver;
> 
>  	u32	status;
>  #define USBHSG_STATUS_STARTED		(1 << 0)
> @@ -882,12 +884,25 @@ static int usbhsg_gadget_start(struct usb_gadget
> *gadget, {
>  	struct usbhsg_gpriv *gpriv = usbhsg_gadget_to_gpriv(gadget);
>  	struct usbhs_priv *priv = usbhsg_gpriv_to_priv(gpriv);
> +	struct device *dev = usbhs_priv_to_dev(priv);
> +	int ret;
> 
>  	if (!driver		||
>  	    !driver->setup	||
>  	    driver->max_speed < USB_SPEED_FULL)
>  		return -EINVAL;
> 
> +	/* connect to bus through transceiver */
> +	if (!IS_ERR_OR_NULL(gpriv->transceiver)) {
> +		ret = otg_set_peripheral(gpriv->transceiver->otg,
> +					&gpriv->gadget);
> +		if (ret) {
> +			dev_err(dev, "%s: can't bind to transceiver\n",
> +				gpriv->gadget.name);
> +			return ret;
> +		}
> +	}
> +

How is this change related to the topic ? I'm not too familiar with this 
driver so I might just have missed something, but then others could as well, 
and the commit message could do with a bit more information.

>  	/* first hook up the driver ... */
>  	gpriv->driver = driver;
> 
> @@ -900,6 +915,10 @@ static int usbhsg_gadget_stop(struct usb_gadget
> *gadget) struct usbhs_priv *priv = usbhsg_gpriv_to_priv(gpriv);
> 
>  	usbhsg_try_stop(priv, USBHSG_STATUS_REGISTERD);
> +
> +	if (!IS_ERR_OR_NULL(gpriv->transceiver))
> +		otg_set_peripheral(gpriv->transceiver->otg, NULL);
> +
>  	gpriv->driver = NULL;
> 
>  	return 0;
> @@ -947,12 +966,27 @@ static int usbhsg_set_selfpowered(struct usb_gadget
> *gadget, int is_self) return 0;
>  }
> 
> +static int usbhsg_vbus_session(struct usb_gadget *gadget, int is_active)
> +{
> +	struct usbhsg_gpriv *gpriv = usbhsg_gadget_to_gpriv(gadget);
> +	struct usbhs_priv *priv = usbhsg_gpriv_to_priv(gpriv);
> +	struct platform_device *pdev = usbhs_priv_to_pdev(priv);
> +
> +	priv->vbus_is_indirect = 1;

vbus_is_indirect is never reset to 0. Shouldn't you set it to 1 (or rather to 
true) in usbhs_mod_gadget_probe() if an external transceiver is found ?

What would you think of implementing and wiring up the get_vbus operation in 
usbhs_mod_gadget_probe() in the same way that usbhs_mod_autonomy_mode() does, 
and return the value of vbus_indirect_value there ? You could then get rid of 
the vbus_is_indirect field and move the vbus_indirect_value field to struct 
usbhsg_gpriv, removing the need to modify drivers/usb/renesas_usbhs/common.c. 
It should also solve the race condition mentioned above.

> +	priv->vbus_indirect_value = !!is_active;
> +
> +	renesas_usbhs_call_notify_hotplug(pdev);
> +
> +	return 0;
> +}
> +
>  static const struct usb_gadget_ops usbhsg_gadget_ops = {
>  	.get_frame		= usbhsg_get_frame,
>  	.set_selfpowered	= usbhsg_set_selfpowered,
>  	.udc_start		= usbhsg_gadget_start,
>  	.udc_stop		= usbhsg_gadget_stop,
>  	.pullup			= usbhsg_pullup,
> +	.vbus_session		= usbhsg_vbus_session,
>  };
> 
>  static int usbhsg_start(struct usbhs_priv *priv)
> @@ -994,6 +1028,10 @@ int usbhs_mod_gadget_probe(struct usbhs_priv *priv)
>  		goto usbhs_mod_gadget_probe_err_gpriv;
>  	}
> 
> +	gpriv->transceiver = usb_get_phy(USB_PHY_TYPE_UNDEFINED);
> +	dev_info(dev, "%s transceiver found\n",
> +		 gpriv->transceiver ? "" : "No");
> +
>  	/*
>  	 * CAUTION
>  	 *

-- 
Regards,

Laurent Pinchart