rtl8xxxu: gen1: Add module parameters to adjust DMA aggregation parameters

This allows the user to specify DMA aggregation timout and block
count. Blocks are presumably always 512 bytes, so the minimum block
count is 6 for 802.11 packets.
Signed-off-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/realtek/rtl8xxxu/rtl8xxxu_core.c

@@ -45,6 +45,8 @@
 int rtl8xxxu_debug = RTL8XXXU_DEBUG_EFUSE;
 static bool rtl8xxxu_ht40_2g;
 static bool rtl8xxxu_dma_aggregation;
+static int rtl8xxxu_dma_agg_timeout = -1;
+static int rtl8xxxu_dma_agg_pages = -1;
 
 MODULE_AUTHOR("Jes Sorensen <Jes.Sorensen@redhat.com>");
 MODULE_DESCRIPTION("RTL8XXXu USB mac80211 Wireless LAN Driver");
@@ -65,6 +67,10 @@ module_param_named(ht40_2g, rtl8xxxu_ht40_2g, bool, 0600);
 MODULE_PARM_DESC(ht40_2g, "Enable HT40 support on the 2.4GHz band");
 module_param_named(dma_aggregation, rtl8xxxu_dma_aggregation, bool, 0600);
 MODULE_PARM_DESC(dma_aggregation, "Enable DMA packet aggregation");
+module_param_named(dma_agg_timeout, rtl8xxxu_dma_agg_timeout, int, 0600);
+MODULE_PARM_DESC(dma_agg_timeout, "Set DMA aggregation timeout (range 1-127)");
+module_param_named(dma_agg_pages, rtl8xxxu_dma_agg_pages, int, 0600);
+MODULE_PARM_DESC(dma_agg_pages, "Set DMA aggregation pages (range 1-127, 0 to disable)");
 
 #define USB_VENDOR_ID_REALTEK		0x0bda
 #define RTL8XXXU_RX_URBS		32
@@ -4441,6 +4447,18 @@ void rtl8xxxu_gen1_init_aggregation(struct rtl8xxxu_priv *priv)
 	 */
 
 	page_thresh = (priv->fops->rx_agg_buf_size / 512);
+	if (rtl8xxxu_dma_agg_pages >= 0) {
+		if (rtl8xxxu_dma_agg_pages <= page_thresh)
+			timeout = page_thresh;
+		else if (rtl8xxxu_dma_agg_pages <= 6)
+			dev_err(&priv->udev->dev,
+				"%s: dma_agg_pages=%i too small, minium is 6\n",
+				__func__, rtl8xxxu_dma_agg_pages);
+		else
+			dev_err(&priv->udev->dev,
+				"%s: dma_agg_pages=%i larger than limit %i\n",
+				__func__, rtl8xxxu_dma_agg_pages, page_thresh);
+	}
 	rtl8xxxu_write8(priv, REG_RXDMA_AGG_PG_TH, page_thresh);
 	/*
 	 * REG_RXDMA_AGG_PG_TH + 1 seems to be the timeout register on
@@ -4448,6 +4466,16 @@ void rtl8xxxu_gen1_init_aggregation(struct rtl8xxxu_priv *priv)
 	 * don't set it, so better set both.
 	 */
 	timeout = 4;
+
+	if (rtl8xxxu_dma_agg_timeout >= 0) {
+		if (rtl8xxxu_dma_agg_timeout <= 127)
+			timeout = rtl8xxxu_dma_agg_timeout;
+		else
+			dev_err(&priv->udev->dev,
+				"%s: Invalid dma_agg_timeout: %i\n",
+				__func__, rtl8xxxu_dma_agg_timeout);
+	}
+
 	rtl8xxxu_write8(priv, REG_RXDMA_AGG_PG_TH + 1, timeout);
 	rtl8xxxu_write8(priv, REG_USB_DMA_AGG_TO, timeout);
 	priv->rx_buf_aggregation = 1;