Use DMA for transfers.

Author: martinling

firmware/hackrf_usb/usb_api_transceiver.c

@@ -26,7 +26,11 @@
 #include <stdbool.h>
 #include <stddef.h>
 
+#include <libopencm3/lpc43xx/m4/nvic.h>
+#include <libopencm3/cm3/nvic.h>
+
 #include <fixed_point.h>
+#include <gpdma.h>
 #include <hackrf_core.h>
 #include <hackrf_ui.h>
 #include <m0_state.h>
@@ -75,6 +79,8 @@ typedef struct {
 
 set_sample_r_params_t set_sample_r_params;
 
+void transceiver_dma_setup(void);
+
 usb_request_status_t usb_vendor_request_set_baseband_filter_bandwidth(
 	usb_endpoint_t* const endpoint,
 	const usb_transfer_stage_t stage)
@@ -347,6 +353,8 @@ void transceiver_startup(const transceiver_mode_t mode)
 	usb_started = 0;
 	usb_completed = 0;
 
+	transceiver_dma_setup();
+
 	radio_switch_opmode(&radio, mode);
 
 	hackrf_ui()->set_transceiver_mode(mode);
@@ -460,15 +468,63 @@ usb_request_status_t usb_vendor_request_get_buffer_size(
 	return USB_REQUEST_STATUS_OK;
 }
 
+/* clang-format off */
+
+// Which GPDMA channel to use.
+const uint32_t DMA_CHANNEL = 1;
+
+// GPDMA CCONFIG register setting.
+const uint32_t DMA_CONFIG =
+	  GPDMA_CCONFIG_FLOWCNTRL(0) // memory-to-memory
+	| GPDMA_CCONFIG_IE(0)        // no error interrupt
+	| GPDMA_CCONFIG_ITC(1)       // terminal count interrupt
+	| GPDMA_CCONFIG_L(0)         // do not lock
+	| GPDMA_CCONFIG_H(0);        // do not halt
+
+// GPDMA CCONTROL register setting (excluding TRANSFERSIZE field).
+const uint32_t DMA_CONTROL =
+	  GPDMA_CCONTROL_SBSIZE(7) // 256-transfer src bursts
+	| GPDMA_CCONTROL_DBSIZE(7) // 256-transfer dst bursts
+	| GPDMA_CCONTROL_SWIDTH(2) // 32-bit src transfers
+	| GPDMA_CCONTROL_DWIDTH(2) // 32-bit dst transfers
+	| GPDMA_CCONTROL_S(0)      // AHB Master 0
+	| GPDMA_CCONTROL_D(1)      // AHB Master 1
+	| GPDMA_CCONTROL_SI(1)     // increment source
+	| GPDMA_CCONTROL_DI(1)     // increment destination
+	| GPDMA_CCONTROL_PROT1(0)  // user mode
+	| GPDMA_CCONTROL_PROT2(0)  // not bufferable
+	| GPDMA_CCONTROL_PROT3(0)  // not cacheable
+	| GPDMA_CCONTROL_I(1);     // interrupt enabled
+
+/* clang-format on */
+
+// Called before any sequence of DMA transfers.
+void transceiver_dma_setup(void)
+{
+	gpdma_controller_enable();
+	GPDMA_CCONFIG(DMA_CHANNEL) = DMA_CONFIG;
+	GPDMA_CCONTROL(DMA_CHANNEL) = DMA_CONTROL;
+	GPDMA_CLLI(DMA_CHANNEL) = 0;
+	GPDMA_INTTCCLEAR = (1 << DMA_CHANNEL);
+	nvic_enable_irq(NVIC_DMA_IRQ);
+}
+
+// Called to start each DMA transfer.
 void transceiver_start_dma(void* src, void* dest, size_t size)
 {
+	uint32_t num_transfers = size >> 2;
+	GPDMA_CCONTROL(DMA_CHANNEL) = DMA_CONTROL | num_transfers;
+	GPDMA_CSRCADDR(DMA_CHANNEL) = (uint32_t) src;
+	GPDMA_CDESTADDR(DMA_CHANNEL) = (uint32_t) dest;
 	dma_pending = size;
-	memcpy(dest, src, size);
-	dma_isr();
+	gpdma_channel_enable(DMA_CHANNEL);
 }
 
+// Called when a DMA transfer completes.
 void dma_isr(void)
 {
+	gpdma_channel_disable(DMA_CHANNEL);
+	GPDMA_INTTCCLEAR = (1 << DMA_CHANNEL);
 	m0_state.m4_count += dma_pending;
 	dma_pending = 0;
 }