qmi_wwan: add support for Quectel EC21 and EC25

The Quectel EC21 and EC25 need the same "set DTR" request as devices
based on the MDM9230 chipset, but has no USB3 support. Our best guess
is that the "set DTR" functionality depends on chipset and/or
baseband firmware generation. But USB3 is still an optional feature.

Since we cannot enable this unconditionally for all older devices, and
there doesn't appear to be anything we can use in the USB descriptors
to identify these chips, we are forced to use a device specific quirk
flag.

Reported-and-tested-by: Sebastian Sjoholm <[e-mail]>
Signed-off-by: Bjørn Mork <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/usb/qmi_wwan.c

···
 	QMI_WWAN_FLAG_RAWIP = 1 << 0,
 };
 
+enum qmi_wwan_quirks {
+	QMI_WWAN_QUIRK_DTR = 1 << 0,	/* needs "set DTR" request */
+};
+
 static void qmi_wwan_netdev_setup(struct net_device *net)
 {
 	struct usbnet *dev = netdev_priv(net);
···
 	 * clearing out state the clients might need.
 	 *
 	 * MDM9x30 is the first QMI chipset with USB3 support. Abuse
-	 * this fact to enable the quirk.
+	 * this fact to enable the quirk for all USB3 devices.
+	 *
+	 * There are also chipsets with the same "set DTR" requirement
+	 * but without USB3 support.  Devices based on these chips
+	 * need a quirk flag in the device ID table.
 	 */
-	if (le16_to_cpu(dev->udev->descriptor.bcdUSB) >= 0x0201) {
+	if (dev->driver_info->data & QMI_WWAN_QUIRK_DTR ||
+	    le16_to_cpu(dev->udev->descriptor.bcdUSB) >= 0x0201) {
 		qmi_wwan_manage_power(dev, 1);
 		qmi_wwan_change_dtr(dev, true);
 	}
···
 	.rx_fixup       = qmi_wwan_rx_fixup,
 };
 
+static const struct driver_info	qmi_wwan_info_quirk_dtr = {
+	.description	= "WWAN/QMI device",
+	.flags		= FLAG_WWAN,
+	.bind		= qmi_wwan_bind,
+	.unbind		= qmi_wwan_unbind,
+	.manage_power	= qmi_wwan_manage_power,
+	.rx_fixup       = qmi_wwan_rx_fixup,
+	.data           = QMI_WWAN_QUIRK_DTR,
+};
+
 #define HUAWEI_VENDOR_ID	0x12D1
 
 /* map QMI/wwan function by a fixed interface number */
 #define QMI_FIXED_INTF(vend, prod, num) \
 	USB_DEVICE_INTERFACE_NUMBER(vend, prod, num), \
 	.driver_info = (unsigned long)&qmi_wwan_info
+
+/* devices requiring "set DTR" quirk */
+#define QMI_QUIRK_SET_DTR(vend, prod, num) \
+	USB_DEVICE_INTERFACE_NUMBER(vend, prod, num), \
+	.driver_info = (unsigned long)&qmi_wwan_info_quirk_dtr
 
 /* Gobi 1000 QMI/wwan interface number is 3 according to qcserial */
 #define QMI_GOBI1K_DEVICE(vend, prod) \
···
 	{QMI_FIXED_INTF(0x03f0, 0x4e1d, 8)},	/* HP lt4111 LTE/EV-DO/HSPA+ Gobi 4G Module */
 	{QMI_FIXED_INTF(0x22de, 0x9061, 3)},	/* WeTelecom WPD-600N */
 	{QMI_FIXED_INTF(0x1e0e, 0x9001, 5)},	/* SIMCom 7230E */
+	{QMI_QUIRK_SET_DTR(0x2c7c, 0x0125, 4)},	/* Quectel EC25, EC20 R2.0  Mini PCIe */
+	{QMI_QUIRK_SET_DTR(0x2c7c, 0x0121, 4)},	/* Quectel EC21 Mini PCIe */
 
 	/* 4. Gobi 1000 devices */
 	{QMI_GOBI1K_DEVICE(0x05c6, 0x9212)},	/* Acer Gobi Modem Device */