Re: [PATCH v3 5/5] Bluetooth: btusb: Use the hw_reset method to allow resetting the BT chip

[Rajat Jain]

Hi Marcel,

Thanks for your review.

On Fri, Jan 18, 2019 at 3:04 AM Marcel Holtmann <marcel@xxxxxxxxxxxx> wrote:
>
> Hi Rajat,
>
> > If the platform provides it, use the reset gpio to reset the BT
> > chip (requested by the HCI core if needed). This has been found helpful
> > on some of Intel bluetooth controllers where the firmware gets stuck and
> > the only way out is a hard reset pin provided by the platform.
> >
> > Signed-off-by: Rajat Jain <rajatja@xxxxxxxxxx>
> > ---
> > v3: Better error handling for gpiod_get_optional()
> > v2: Handle the EPROBE_DEFER case.
> >
> > drivers/bluetooth/btusb.c | 40 +++++++++++++++++++++++++++++++++++++++
> > 1 file changed, 40 insertions(+)
> >
> > diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
> > index e8e148480c91..e7631f770fae 100644
> > --- a/drivers/bluetooth/btusb.c
> > +++ b/drivers/bluetooth/btusb.c
> > @@ -29,6 +29,7 @@
> > #include <linux/of_device.h>
> > #include <linux/of_irq.h>
> > #include <linux/suspend.h>
> > +#include <linux/gpio/consumer.h>
> > #include <asm/unaligned.h>
> >
> > #include <net/bluetooth/bluetooth.h>
> > @@ -475,6 +476,8 @@ struct btusb_data {
> >       struct usb_endpoint_descriptor *diag_tx_ep;
> >       struct usb_endpoint_descriptor *diag_rx_ep;
> >
> > +     struct gpio_desc *reset_gpio;
> > +
> >       __u8 cmdreq_type;
> >       __u8 cmdreq;
> >
> > @@ -490,6 +493,26 @@ struct btusb_data {
> >       int oob_wake_irq;   /* irq for out-of-band wake-on-bt */
> > };
> >
> > +
> > +static void btusb_hw_reset(struct hci_dev *hdev)
> > +{
> > +     struct btusb_data *data = hci_get_drvdata(hdev);
> > +     struct gpio_desc *reset_gpio = data->reset_gpio;
> > +
> > +     /*
> > +      * Toggle the hard reset line if the platform provides one. The reset
> > +      * is going to yank the device off the USB and then replug. So doing
> > +      * once is enough. The cleanup is handled correctly on the way out
> > +      * (standard USB disconnect), and the new device is detected cleanly
> > +      * and bound to the driver again like it should be.
> > +      */
> > +     bt_dev_dbg(hdev, "%s: Initiating HW reset via gpio", __func__);
>
> No __func__ here. That bt_dev_dbg does all of that via dynamic debug already.

Will fix.

>
> > +     clear_bit(HCI_QUIRK_HW_RESET_ON_TIMEOUT, &hdev->quirks);
> > +     gpiod_set_value(reset_gpio, 1);
> > +     mdelay(100);
> > +     gpiod_set_value(reset_gpio, 0);
> > +}
> > +
> > static inline void btusb_free_frags(struct btusb_data *data)
> > {
> >       unsigned long flags;
> > @@ -2917,6 +2940,7 @@ static int btusb_probe(struct usb_interface *intf,
> >                      const struct usb_device_id *id)
> > {
> >       struct usb_endpoint_descriptor *ep_desc;
> > +     struct gpio_desc *reset_gpio;
> >       struct btusb_data *data;
> >       struct hci_dev *hdev;
> >       unsigned ifnum_base;
> > @@ -3030,6 +3054,16 @@ static int btusb_probe(struct usb_interface *intf,
> >
> >       SET_HCIDEV_DEV(hdev, &intf->dev);
> >
> > +     reset_gpio = gpiod_get_optional(&data->udev->dev, "reset",
> > +                                     GPIOD_OUT_LOW);
> > +     if (IS_ERR(reset_gpio)) {
> > +             err = PTR_ERR(reset_gpio);
> > +             goto out_free_dev;
> > +     } else if (reset_gpio) {
> > +             data->reset_gpio = reset_gpio;
> > +             hdev->hw_reset = btusb_hw_reset;
> > +     }
> > +
>
> How do we ensure that this is the right âresetâ line. And it also needs to be bound to some hardware unless
> we can guarantee that this is always the same.

The BIOS / ACPI ensures that. The kernel driver just uses the ACPI
provided reset line.

>
> >       hdev->open   = btusb_open;
> >       hdev->close  = btusb_close;
> >       hdev->flush  = btusb_flush;
> > @@ -3085,6 +3119,7 @@ static int btusb_probe(struct usb_interface *intf,
> >               set_bit(HCI_QUIRK_STRICT_DUPLICATE_FILTER, &hdev->quirks);
> >               set_bit(HCI_QUIRK_SIMULTANEOUS_DISCOVERY, &hdev->quirks);
> >               set_bit(HCI_QUIRK_NON_PERSISTENT_DIAG, &hdev->quirks);
> > +             set_bit(HCI_QUIRK_HW_RESET_ON_TIMEOUT, &hdev->quirks);
>
> You are not messing with the quirks here please. Clearing quirks is crazy. Use the data->flags since this should be all btusb.c specific.

Do I understand it right that you do not want me to clear the quirks
in btusb_hw_reset() and use data->flags instead? Sure, I will do that.
But I'm not sure if that's all you meant, because you commented on
btusb_probe() code where I'm setting the quirk (not clearing it) so
that the hci core can call the hw_reset() callback on timeout.

Thanks,

Rajat
>
> >
> >               if (id->driver_info & BTUSB_INTEL) {
> >                       hdev->setup = btusb_setup_intel;
> > @@ -3225,6 +3260,8 @@ static int btusb_probe(struct usb_interface *intf,
> >       return 0;
> >
> > out_free_dev:
> > +     if (data->reset_gpio)
> > +             gpiod_put(data->reset_gpio);
> >       hci_free_dev(hdev);
> >       return err;
> > }
> > @@ -3268,6 +3305,9 @@ static void btusb_disconnect(struct usb_interface *intf)
> >       if (data->oob_wake_irq)
> >               device_init_wakeup(&data->udev->dev, false);
> >
> > +     if (data->reset_gpio)
> > +             gpiod_put(data->reset_gpio);
> > +
> >       hci_free_dev(hdev);
> > }
>
> Regards
>
> Marcel
>