Date:   Tue, 24 Jan 2017 13:20:21 -0800
From:   Brian Norris <briannorris@...omium.org>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Marcel Holtmann <marcel@...tmann.org>,
        Gustavo Padovan <gustavo@...ovan.org>,
        Johan Hedberg <johan.hedberg@...il.com>,
        Amitkumar Karwar <akarwar@...vell.com>,
        Wei-Ning Huang <wnhuang@...omium.org>,
        Xinming Hu <huxm@...vell.com>, netdev@...r.kernel.org,
        devicetree@...r.kernel.org, linux-bluetooth@...r.kernel.org,
        linux-kernel@...r.kernel.org, rajatxjain@...il.com
Subject: Re: [PATCH v5 2/3] Bluetooth: btusb: Add out-of-band wakeup support

Hi Rajat,

On Thu, Jan 12, 2017 at 10:01:06AM -0800, Rajat Jain wrote:
> Some onboard BT chips (e.g. Marvell 8997) contain a wakeup pin that
> can be connected to a gpio on the CPU side, and can be used to wakeup
> the host out-of-band. This can be useful in situations where the
> in-band wakeup is not possible or not preferable (e.g. the in-band
> wakeup may require the USB host controller to remain active, and
> hence consuming more system power during system sleep).
> 
> The oob gpio interrupt to be used for wakeup on the CPU side, is
> read from the device tree node, (using standard interrupt descriptors).
> A devcie tree binding document is also added for the driver. The
> compatible string is in compliance with
> Documentation/devicetree/bindings/usb/usb-device.txt
> 
> Signed-off-by: Rajat Jain <rajatja@...gle.com>
> Reviewed-by: Brian Norris <briannorris@...omium.org>
> Acked-by: Rob Herring <robh@...nel.org>
> ---
> v5: Move the call to pm_wakeup_event() to the begining of irq handler.
> v4: Move the set_bit(BTUSB_OOB_WAKE_DISABLED,..) call to the beginning of
>     btusb_config_oob_wake()
> v3: Add Brian's "Reviewed-by"
> v2: * Use interrupt-names ("wakeup") instead of assuming first interrupt.
>     * Leave it on device tree to specify IRQ flags (level /edge triggered)
>     * Mark the device as non wakeable on exit.
> 
>  Documentation/devicetree/bindings/net/btusb.txt | 40 ++++++++++++
>  drivers/bluetooth/btusb.c                       | 85 +++++++++++++++++++++++++
>  2 files changed, 125 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/net/btusb.txt
> 
> diff --git a/Documentation/devicetree/bindings/net/btusb.txt b/Documentation/devicetree/bindings/net/btusb.txt
> new file mode 100644
> index 000000000000..2c0355c85972
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/net/btusb.txt
> @@ -0,0 +1,40 @@
> +Generic Bluetooth controller over USB (btusb driver)
> +---------------------------------------------------
> +
> +Required properties:
> +
> +  - compatible : should comply with the format "usbVID,PID" specified in
> +		 Documentation/devicetree/bindings/usb/usb-device.txt
> +		 At the time of writing, the only OF supported devices
> +		 (more may be added later) are:
> +
> +		  "usb1286,204e" (Marvell 8997)
> +
> +Optional properties:
> +
> +  - interrupt-parent: phandle of the parent interrupt controller
> +  - interrupt-names: (see below)
> +  - interrupts : The interrupt specified by the name "wakeup" is the interrupt
> +		 that shall be used for out-of-band wake-on-bt. Driver will
> +		 request this interrupt for wakeup. During system suspend, the
> +		 irq will be enabled so that the bluetooth chip can wakeup host
> +		 platform out of band. During system resume, the irq will be
> +		 disabled to make sure unnecessary interrupt is not received.
> +
> +Example:
> +
> +Following example uses irq pin number 3 of gpio0 for out of band wake-on-bt:
> +
> +&usb_host1_ehci {
> +    status = "okay";
> +    #address-cells = <1>;
> +    #size-cells = <0>;
> +
> +    mvl_bt1: bt@1 {
> +	compatible = "usb1286,204e";
> +	reg = <1>;
> +	interrupt-parent = <&gpio0>;
> +	interrupt-name = "wakeup";
> +	interrupts = <3 IRQ_TYPE_LEVEL_LOW>;
> +    };
> +};
> diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> index ce22cefceed1..0a777bb407b1 100644
> --- a/drivers/bluetooth/btusb.c
> +++ b/drivers/bluetooth/btusb.c
> @@ -24,6 +24,8 @@
>  #include <linux/module.h>
>  #include <linux/usb.h>
>  #include <linux/firmware.h>
> +#include <linux/of_device.h>
> +#include <linux/of_irq.h>
>  #include <asm/unaligned.h>
>  
>  #include <net/bluetooth/bluetooth.h>
> @@ -369,6 +371,7 @@ static const struct usb_device_id blacklist_table[] = {
>  #define BTUSB_BOOTING		9
>  #define BTUSB_RESET_RESUME	10
>  #define BTUSB_DIAG_RUNNING	11
> +#define BTUSB_OOB_WAKE_DISABLED	12
>  
>  struct btusb_data {
>  	struct hci_dev       *hdev;
> @@ -416,6 +419,8 @@ struct btusb_data {
>  	int (*recv_bulk)(struct btusb_data *data, void *buffer, int count);
>  
>  	int (*setup_on_usb)(struct hci_dev *hdev);
> +
> +	int oob_wake_irq;   /* irq for out-of-band wake-on-bt */
>  };
>  
>  static inline void btusb_free_frags(struct btusb_data *data)
> @@ -2728,6 +2733,66 @@ static int btusb_bcm_set_diag(struct hci_dev *hdev, bool enable)
>  }
>  #endif
>  
> +#ifdef CONFIG_PM
> +static irqreturn_t btusb_oob_wake_handler(int irq, void *priv)
> +{
> +	struct btusb_data *data = priv;
> +
> +	pm_wakeup_event(&data->udev->dev, 0);
> +
> +	/* Disable only if not already disabled (keep it balanced) */
> +	if (!test_and_set_bit(BTUSB_OOB_WAKE_DISABLED, &data->flags)) {
> +		disable_irq_nosync(irq);
> +		disable_irq_wake(irq);
> +	}
> +	return IRQ_HANDLED;
> +}
> +
> +static const struct of_device_id btusb_match_table[] = {
> +	{ .compatible = "usb1286,204e" },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, btusb_match_table);
> +
> +/* Use an oob wakeup pin? */
> +static int btusb_config_oob_wake(struct hci_dev *hdev)
> +{
> +	struct btusb_data *data = hci_get_drvdata(hdev);
> +	struct device *dev = &data->udev->dev;
> +	int irq, ret;
> +
> +	set_bit(BTUSB_OOB_WAKE_DISABLED, &data->flags);
> +
> +	if (!of_match_device(btusb_match_table, dev))
> +		return 0;
> +
> +	/* Move on if no IRQ specified */
> +	irq = of_irq_get_byname(dev->of_node, "wakeup");
> +	if (irq <= 0) {
> +		bt_dev_dbg(hdev, "%s: no OOB Wakeup IRQ in DT", __func__);
> +		return 0;
> +	}
> +
> +	ret = devm_request_irq(&hdev->dev, irq, btusb_oob_wake_handler,
> +			       0, "OOB Wake-on-BT", data);
> +	if (ret) {
> +		bt_dev_err(hdev, "%s: IRQ request failed", __func__);
> +		return ret;
> +	}
> +
> +	ret = device_init_wakeup(dev, true);
> +	if (ret) {
> +		bt_dev_err(hdev, "%s: failed to init_wakeup\n", __func__);

bt_dev_err() includes the newlines for you, but you'd added an extra one
here (but not above).

> +		return ret;
> +	}
> +
> +	data->oob_wake_irq = irq;
> +	disable_irq(irq);
> +	bt_dev_info(hdev, "OOB Wake-on-BT configured at IRQ %u\n", irq);

And here.

> +	return 0;
> +}
> +#endif
> +
>  static int btusb_probe(struct usb_interface *intf,
>  		       const struct usb_device_id *id)
>  {
> @@ -2849,6 +2914,11 @@ static int btusb_probe(struct usb_interface *intf,
>  	hdev->send   = btusb_send_frame;
>  	hdev->notify = btusb_notify;
>  
> +#ifdef CONFIG_PM
> +	err = btusb_config_oob_wake(hdev);
> +	if (err)
> +		goto out_free_dev;
> +#endif
>  	if (id->driver_info & BTUSB_CW6622)
>  		set_bit(HCI_QUIRK_BROKEN_STORED_LINK_KEY, &hdev->quirks);
>  
> @@ -3061,6 +3131,9 @@ static void btusb_disconnect(struct usb_interface *intf)
>  			usb_driver_release_interface(&btusb_driver, data->isoc);
>  	}
>  
> +	if (data->oob_wake_irq)
> +		device_init_wakeup(&data->udev->dev, false);
> +
>  	hci_free_dev(hdev);
>  }
>  
> @@ -3089,6 +3162,12 @@ static int btusb_suspend(struct usb_interface *intf, pm_message_t message)
>  	btusb_stop_traffic(data);
>  	usb_kill_anchored_urbs(&data->tx_anchor);
>  
> +	if (data->oob_wake_irq && device_may_wakeup(&data->udev->dev)) {
> +		clear_bit(BTUSB_OOB_WAKE_DISABLED, &data->flags);
> +		enable_irq_wake(data->oob_wake_irq);
> +		enable_irq(data->oob_wake_irq);
> +	}
> +
>  	/* Optionally request a device reset on resume, but only when
>  	 * wakeups are disabled. If wakeups are enabled we assume the
>  	 * device will stay powered up throughout suspend.
> @@ -3126,6 +3205,12 @@ static int btusb_resume(struct usb_interface *intf)
>  	if (--data->suspend_count)
>  		return 0;
>  
> +	/* Disable only if not already disabled (keep it balanced) */
> +	if (!test_and_set_bit(BTUSB_OOB_WAKE_DISABLED, &data->flags)) {

As I mentioned elsewhere, the negative form (i.e., DISABLED instead of
ENABLED) seems a little backward to me. It has the small effect of
meaning that the default behavior is actually to pretend that OOB wake
was enabled, and so if somehow btusb_config_oob_wake() wasn't called
(e.g., if CONFIG_PM is not enabled, or if the code gets refactored) this
then btusb_resume() will behave badly.

Now, this doesn't create an immediate problem (btusb_resume() should
never be called if !CONFIG_PM), but it does suggest that maybe it would
be better for the default (0) value to mean "disabled".

Brian

> +		disable_irq(data->oob_wake_irq);
> +		disable_irq_wake(data->oob_wake_irq);
> +	}
> +
>  	if (!test_bit(HCI_RUNNING, &hdev->flags))
>  		goto done;
>  
> -- 
> 2.11.0.390.gc69c2f50cf-goog
> 

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