Re: [PATCH RESEND 1/1] usb: serial: option: add ZLP support for 0x1bc7/0x9010

From: Johan Hovold <johan@kernel.org>
To: Daniele Palmas <dnlplm@gmail.com>
Cc: Johan Hovold <johan@kernel.org>, linux-usb@vger.kernel.org
Subject: Re: [PATCH RESEND 1/1] usb: serial: option: add ZLP support for 0x1bc7/0x9010
Date: Thu, 5 Dec 2019 15:57:31 +0100	[thread overview]
Message-ID: <20191205145731.GM10631@localhost> (raw)
In-Reply-To: <20191118133251.21401-1-dnlplm@gmail.com>

On Mon, Nov 18, 2019 at 02:32:51PM +0100, Daniele Palmas wrote:
> Telit FN980 flashing device 0x1bc7/0x9010 requires zero packet
> to be sent if out data size is equal to the endpoint max size.
> 
> Signed-off-by: Daniele Palmas <dnlplm@gmail.com>
> ---
>  drivers/usb/serial/option.c   | 8 ++++++++
>  drivers/usb/serial/usb-wwan.h | 1 +
>  drivers/usb/serial/usb_wwan.c | 9 +++++++++
>  3 files changed, 18 insertions(+)
> 
> diff --git a/drivers/usb/serial/option.c b/drivers/usb/serial/option.c
> index e9491d400a24..c13e063cb399 100644
> --- a/drivers/usb/serial/option.c
> +++ b/drivers/usb/serial/option.c
> @@ -567,6 +567,9 @@ static void option_instat_callback(struct urb *urb);
>  /* Interface must have two endpoints */
>  #define NUMEP2		BIT(16)
>  
> +/* Device needs ZLP */
> +#define ZLP		BIT(17)
> +
>  
>  static const struct usb_device_id option_ids[] = {
>  	{ USB_DEVICE(OPTION_VENDOR_ID, OPTION_PRODUCT_COLT) },
> @@ -1196,6 +1199,8 @@ static const struct usb_device_id option_ids[] = {
>  	  .driver_info = NCTRL(0) | RSVD(1) },
>  	{ USB_DEVICE_INTERFACE_CLASS(TELIT_VENDOR_ID, 0x1901, 0xff),	/* Telit LN940 (MBIM) */
>  	  .driver_info = NCTRL(0) },
> +	{ USB_DEVICE(TELIT_VENDOR_ID, 0x9010),				/* Telit SBL FN980 flashing device */
> +	  .driver_info = NCTRL(0) | ZLP },

Hmm. Could you post the lsusb -v output for this device?

I wonder whether using option is the right thing to do here. We're just
currently throwing everything modem related in here it seems. :)

>  	{ USB_DEVICE_AND_INTERFACE_INFO(ZTE_VENDOR_ID, ZTE_PRODUCT_MF622, 0xff, 0xff, 0xff) }, /* ZTE WCDMA products */
>  	{ USB_DEVICE_AND_INTERFACE_INFO(ZTE_VENDOR_ID, 0x0002, 0xff, 0xff, 0xff),
>  	  .driver_info = RSVD(1) },
> @@ -2097,6 +2102,9 @@ static int option_attach(struct usb_serial *serial)
>  	if (!(device_flags & NCTRL(iface_desc->bInterfaceNumber)))
>  		data->use_send_setup = 1;
>  
> +	if (device_flags & ZLP)
> +		data->use_zlp = 1;
> +
>  	spin_lock_init(&data->susp_lock);
>  
>  	usb_set_serial_data(serial, data);
> diff --git a/drivers/usb/serial/usb-wwan.h b/drivers/usb/serial/usb-wwan.h
> index 1c120eaf4091..934e9361cf6b 100644
> --- a/drivers/usb/serial/usb-wwan.h
> +++ b/drivers/usb/serial/usb-wwan.h
> @@ -38,6 +38,7 @@ struct usb_wwan_intf_private {
>  	spinlock_t susp_lock;
>  	unsigned int suspended:1;
>  	unsigned int use_send_setup:1;
> +	unsigned int use_zlp:1;
>  	int in_flight;
>  	unsigned int open_ports;
>  	void *private;
> diff --git a/drivers/usb/serial/usb_wwan.c b/drivers/usb/serial/usb_wwan.c
> index 7e855c87e4f7..8066b5e2d305 100644
> --- a/drivers/usb/serial/usb_wwan.c
> +++ b/drivers/usb/serial/usb_wwan.c
> @@ -228,6 +228,15 @@ int usb_wwan_write(struct tty_struct *tty, struct usb_serial_port *port,
>  		} else {
>  			intfdata->in_flight++;
>  			spin_unlock_irqrestore(&intfdata->susp_lock, flags);
> +			if (intfdata->use_zlp) {
> +				unsigned int ep_maxp;
> +
> +				ep_maxp = usb_maxpacket(port->serial->dev,
> +							this_urb->pipe, 1);
> +
> +				if (ep_maxp && (todo % ep_maxp == 0))
> +					this_urb->transfer_flags |= URB_ZERO_PACKET;

No need to do the transfer_length calculations here, the host-controller
driver will take care of that. Just set URB_ZERO_PACKET unconditionally
if the device requires it.

> +			}
>  			err = usb_submit_urb(this_urb, GFP_ATOMIC);
>  			if (err) {
>  				dev_err(&port->dev,

Johan