Some latest QC based modems seem not to properly accept altsetting
toggling in cdc_ncm_bind_common, making them to fail. The workaround
was to introduce an empirically decided pause to avoid the failure.
This patch introduces a different approach: for MBIM devices, instead
of toggling interfaces, the MBIM class-specific request code
RESET_FUNCTION is used in order to reset the function to its initial
state, removing the need for the pause.
Signed-off-by: Daniele Palmas <dnlplm@xxxxxxxxx>
---
drivers/net/usb/cdc_ncm.c | 39 +++++++++++++++++++++++++++------------
include/uapi/linux/usb/cdc.h | 1 +
2 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index 877c951..e8a7a76 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -498,6 +498,22 @@ static int cdc_ncm_init(struct usbnet *dev)
return err; /* GET_NTB_PARAMETERS is required */
}
+ /* Some modems (e.g. Telit LE922A6) need to reset the MBIM function
+ * or they will fail to work properly.
+ * For details on RESET_FUNCTION request see document
+ * "USB Communication Class Subclass Specification for MBIM"
+ * RESET_FUNCTION should be harmless for all the other MBIM modems
+ */
+ if (cdc_ncm_comm_intf_is_mbim(ctx->control->cur_altsetting)) {
+ err = usbnet_write_cmd(dev, USB_CDC_RESET_FUNCTION,
+ USB_TYPE_CLASS | USB_DIR_OUT
+ | USB_RECIP_INTERFACE,
+ 0, iface_no, NULL, 0);
+ if (err < 0) {
+ dev_err(&dev->intf->dev, "failed RESET_FUNCTION\n");
+ }
+ }
+
/* set CRC Mode */
if (cdc_ncm_flags(dev) & USB_CDC_NCM_NCAP_CRC_MODE) {
dev_dbg(&dev->intf->dev, "Setting CRC mode off\n");
@@ -842,25 +858,24 @@ int cdc_ncm_bind_common(struct usbnet *dev, struct usb_interface *intf, u8 data_
/* Reset data interface. Some devices will not reset properly
* unless they are configured first. Toggle the altsetting to
* force a reset
+ * This is applied only to ncm devices, since it has been verified
+ * to cause issues with some MBIM modems (e.g. Telit LE922A6).
+ * MBIM devices reset is achieved using MBIM request RESET_FUNCTION
+ * in cdc_ncm_init
*/
- usb_set_interface(dev->udev, iface_no, data_altsetting);
- temp = usb_set_interface(dev->udev, iface_no, 0);
- if (temp) {
- dev_dbg(&intf->dev, "set interface failed\n");
- goto error2;
+ if (!cdc_ncm_comm_intf_is_mbim(intf->cur_altsetting)) {
+ usb_set_interface(dev->udev, iface_no, data_altsetting);
+ temp = usb_set_interface(dev->udev, iface_no, 0);
+ if (temp) {
+ dev_dbg(&intf->dev, "set interface failed\n");
+ goto error2;
+ }
}
/* initialize basic device settings */
if (cdc_ncm_init(dev))
goto error2;
- /* Some firmwares need a pause here or they will silently fail
- * to set up the interface properly. This value was decided
- * empirically on a Sierra Wireless MC7455 running 02.08.02.00
- * firmware.
- */
- usleep_range(10000, 20000);
-
/* configure data interface */
temp = usb_set_interface(dev->udev, iface_no, data_altsetting);
if (temp) {
diff --git a/include/uapi/linux/usb/cdc.h b/include/uapi/linux/usb/cdc.h
index e2bc417..30258fb 100644
--- a/include/uapi/linux/usb/cdc.h
+++ b/include/uapi/linux/usb/cdc.h
@@ -231,6 +231,7 @@ struct usb_cdc_mbim_extended_desc {
#define USB_CDC_SEND_ENCAPSULATED_COMMAND 0x00
#define USB_CDC_GET_ENCAPSULATED_RESPONSE 0x01
+#define USB_CDC_RESET_FUNCTION 0x05
#define USB_CDC_REQ_SET_LINE_CODING 0x20
#define USB_CDC_REQ_GET_LINE_CODING 0x21
#define USB_CDC_REQ_SET_CONTROL_LINE_STATE 0x22
--
2.7.4
--
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