[PATCH] rtl8xxxu: Fix for agressive power saving by rtl8723bu wireless IC

[John Heenan]

The rtl8723bu wireless IC shows evidence of a more agressive approach to
power saving, powering down its RF side when there is no wireless
interfacing but leaving USB interfacing intact. This makes the wireless
IC more suitable for use in devices which need to keep their power use
as low as practical, such as tablets and Surface Pro type devices.

In effect this means that a full initialisation must be performed
whenever a wireless interface is brought up. It also means that
interpretations of power status from general wireless registers should
not be relied on to influence an init sequence.

The patch works by forcing a fuller initialisation and forcing it to
occur more often in code paths (such as occurs during a low level
authentication that initiates wireless interfacing).

The initialisation sequence is now more consistent with code based
directly on vendor code. For example while the vendor derived code
interprets a register as indcating a particular powered state, it does
not use this information to influence its init sequence.

The rtl8723bu device has a unique USB VID and PID. This is taken
advantage of for the patch to ensure only rtl8723bu devices are affected
by this patch.

With this patch wpa_supplicant reliably and consistently connects with
an AP. Before a workaround such as executing rmmod and modprobe before
each call to wpa_supplicant worked with some distributions.

Signed-off-by: John Heenan <john@xxxxxxxx>
---
 .../net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c  | 24 ++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
index 04141e5..f36e674 100644
--- a/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
+++ b/drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c
@@ -79,6 +79,8 @@ MODULE_PARM_DESC(dma_agg_pages, "Set DMA aggregation pages (range 1-127, 0 to di
 #define RTL8XXXU_TX_URB_LOW_WATER	25
 #define RTL8XXXU_TX_URB_HIGH_WATER	32
 
+#define USB_PRODUCT_ID_RTL8723BU 0xb720
+
 static int rtl8xxxu_submit_rx_urb(struct rtl8xxxu_priv *priv,
 				  struct rtl8xxxu_rx_urb *rx_urb);
 
@@ -3892,6 +3894,7 @@ static int rtl8xxxu_init_device(struct ieee80211_hw *hw)
 	u8 val8;
 	u16 val16;
 	u32 val32;
+  struct usb_device_descriptor *udesc = &priv->udev->descriptor;
 
 	/* Check if MAC is already powered on */
 	val8 = rtl8xxxu_read8(priv, REG_CR);
@@ -3900,7 +3903,9 @@ static int rtl8xxxu_init_device(struct ieee80211_hw *hw)
 	 * Fix 92DU-VC S3 hang with the reason is that secondary mac is not
 	 * initialized. First MAC returns 0xea, second MAC returns 0x00
 	 */
-	if (val8 == 0xea)
+	if (val8 == 0xea
+			|| (udesc->idVendor == USB_VENDOR_ID_REALTEK
+			&&  udesc->idProduct == USB_PRODUCT_ID_RTL8723BU))
 		macpower = false;
 	else
 		macpower = true;
@@ -5776,9 +5781,17 @@ static int rtl8xxxu_start(struct ieee80211_hw *hw)
 	struct rtl8xxxu_tx_urb *tx_urb;
 	unsigned long flags;
 	int ret, i;
+	struct usb_device_descriptor *udesc = &priv->udev->descriptor;
 
 	ret = 0;
 
+	if(udesc->idVendor == USB_VENDOR_ID_REALTEK
+			&& udesc->idProduct == USB_PRODUCT_ID_RTL8723BU) {
+		ret = rtl8xxxu_init_device(hw);
+		if (ret)
+			goto error_out;
+	}
+
 	init_usb_anchor(&priv->rx_anchor);
 	init_usb_anchor(&priv->tx_anchor);
 	init_usb_anchor(&priv->int_anchor);
@@ -6080,9 +6093,12 @@ static int rtl8xxxu_probe(struct usb_interface *interface,
 		goto exit;
 	}
 
-	ret = rtl8xxxu_init_device(hw);
-	if (ret)
+	if(!(id->idVendor == USB_VENDOR_ID_REALTEK
+			&& id->idProduct == USB_PRODUCT_ID_RTL8723BU)) {
+		ret = rtl8xxxu_init_device(hw);
+		if (ret)
 		goto exit;
+	}
 
 	hw->wiphy->max_scan_ssids = 1;
 	hw->wiphy->max_scan_ie_len = IEEE80211_MAX_DATA_LEN;
@@ -6191,7 +6207,7 @@ static struct usb_device_id dev_table[] = {
 /* Tested by Myckel Habets */
 {USB_DEVICE_AND_INTERFACE_INFO(0x2357, 0x0109, 0xff, 0xff, 0xff),
 	.driver_info = (unsigned long)&rtl8192eu_fops},
-{USB_DEVICE_AND_INTERFACE_INFO(USB_VENDOR_ID_REALTEK, 0xb720, 0xff, 0xff, 0xff),
+{USB_DEVICE_AND_INTERFACE_INFO(USB_VENDOR_ID_REALTEK, USB_PRODUCT_ID_RTL8723BU, 0xff, 0xff, 0xff),
 	.driver_info = (unsigned long)&rtl8723bu_fops},
 #ifdef CONFIG_RTL8XXXU_UNTESTED
 /* Still supported by rtlwifi */
-- 
2.10.1