drivers: udc_ambiq: added support double endpoint buffer

implements option to enable double endpoint buffer to improve throughtput
for the endpoints.

Signed-off-by: Chew Zeh Yang <[email protected]>

Author: zeonchew

drivers/usb/udc/Kconfig.ambiq

@@ -72,4 +72,21 @@ config UDC_AMBIQ_ISR_PARAM_COUNT
 	default 5 if SOC_SERIES_APOLLO5X
 	default 3
 
+config UDC_AMBIQ_DEB_ENABLE
+	hex "EP Double Buffer Enable"
+	default 0x0000
+	depends on SOC_SERIES_APOLLO5X
+	help
+	  Double Endpoint Buffer acceleration (DEB) is doubles an EP's FIFO size
+	  so that USB transfer could continue to happen while waiting for DMA/CPU to
+	  load/unload data from the EP FIFO.
+	  This hex value is a bitmap of endpoints for DEB to be enabled. BIT0-4
+	  represents OUT_EP 1-5, while BIT16-20 represents IN_EP 1-8.
+	  Take note that this feature is limited by total EP FIFO size. Proper
+	  calculation should be done before enabling DEB such that the total usage
+	  of FIFO for all endpoint doesn't exceed the FIFO available on SoC.
+	  The list of Soc with its FIFO size is listed below. The FIFO size here
+	  includes 128 bytes required by control endpoints.
+	  - Apollo510: (4096 Bytes FIFO)
+
 endif # UDC_AMBIQ

drivers/usb/udc/udc_ambiq.c

@@ -579,6 +579,36 @@ static int init_apollo5x(const struct udc_ambiq_data *priv)
 }
 #endif
 
+#if CONFIG_UDC_AMBIQ_DEB_ENABLE
+static void init_double_buffers(const struct udc_ambiq_data *priv)
+{
+	uint8_t idx;
+	uint32_t mask;
+
+	idx = 1;
+	mask = CONFIG_UDC_AMBIQ_DEB_ENABLE & 0xFFFF;
+	while (mask) {
+		if (mask & 0x1) {
+			am_hal_usb_enable_ep_double_buffer(priv->usb_handle, idx,
+							   AM_HAL_USB_OUT_DIR, true);
+		}
+		idx++;
+		mask >>= 1;
+	}
+
+	idx = 1;
+	mask = (CONFIG_UDC_AMBIQ_DEB_ENABLE >> 16) & 0xFFFF;
+	while (mask) {
+		if (mask & 0x1) {
+			am_hal_usb_enable_ep_double_buffer(priv->usb_handle, idx, AM_HAL_USB_IN_DIR,
+							   true);
+		}
+		idx++;
+		mask >>= 1;
+	}
+}
+#endif
+
 static int udc_ambiq_init(const struct device *dev)
 {
 	struct udc_ambiq_data *priv = udc_get_private(dev);
@@ -613,6 +643,10 @@ static int udc_ambiq_init(const struct device *dev)
 	}
 #endif
 
+#if CONFIG_UDC_AMBIQ_DEB_ENABLE
+	init_double_buffers(priv);
+#endif
+
 	/* Set USB Speed */
 	am_hal_usb_set_dev_speed(priv->usb_handle, priv->usb_speed);
 	/* Enable USB interrupt */