Add DMA buffer allocation pool.

src/drivers/boards/px4fmu-v2/px4fmu2_init.c

@@ -58,6 +58,7 @@
 #include <nuttx/sdio.h>
 #include <nuttx/mmcsd.h>
 #include <nuttx/analog/adc.h>
+#include <nuttx/gran.h>
 
 #include <stm32.h>
 #include "board_config.h"
@@ -69,6 +70,7 @@
 #include <drivers/drv_led.h>
 
 #include <systemlib/cpuload.h>
+#include <systemlib/perf_counter.h>
 
 /****************************************************************************
  * Pre-Processor Definitions
@@ -76,6 +78,10 @@
 
 /* Configuration ************************************************************/
 
+#if !defined(CONFIG_GRAN) || !defined(CONFIG_FAT_DMAMEMORY)
+# error microSD DMA support requires CONFIG_GRAN and CONFIG_FAT_DMAMEMORY
+#endif
+
 /* Debug ********************************************************************/
 
 #ifdef CONFIG_CPP_HAVE_VARARGS
@@ -96,10 +102,59 @@
  * Protected Functions
  ****************************************************************************/
 
+static GRAN_HANDLE dma_allocator;
+
+/* 
+ * The DMA heap size constrains the total number of things that can be 
+ * ready to do DMA at a time.
+ *
+ * For example, FAT DMA depends on one sector-sized buffer per filesystem plus
+ * one sector-sized buffer per file. 
+ *
+ * We use a fundamental alignment / granule size of 64B; this is sufficient
+ * to guarantee alignment for the largest STM32 DMA burst (16 beats x 32bits).
+ */
+static uint8_t g_dma_heap[8192] __attribute__((aligned(64)));
+static perf_counter_t g_dma_perf;
+
+static void
+dma_alloc_init(void)
+{
+	dma_allocator = gran_initialize(g_dma_heap,
+					sizeof(g_dma_heap),
+					7,  /* 128B granule - must be > alignment (XXX bug?) */
+					6); /* 64B alignment */
+	if (dma_allocator == NULL) {
+		message("[boot] DMA allocator setup FAILED");
+	} else {
+		g_dma_perf = perf_alloc(PC_COUNT, "DMA allocations");
+	}
+}
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
 
+/*
+ * DMA-aware allocator stubs for the FAT filesystem.
+ */
+
+__EXPORT void *fat_dma_alloc(size_t size);
+__EXPORT void fat_dma_free(FAR void *memory, size_t size);
+
+void *
+fat_dma_alloc(size_t size)
+{
+	perf_count(g_dma_perf);
+	return gran_alloc(dma_allocator, size);
+}
+
+void
+fat_dma_free(FAR void *memory, size_t size)
+{
+	gran_free(dma_allocator, memory, size);
+}
+
 /************************************************************************************
  * Name: stm32_boardinitialize
  *
@@ -110,7 +165,8 @@
  *
  ************************************************************************************/
 
-__EXPORT void stm32_boardinitialize(void)
+__EXPORT void
+stm32_boardinitialize(void)
 {
 	/* configure SPI interfaces */
 	stm32_spiinitialize();
@@ -170,6 +226,9 @@ __EXPORT int nsh_archinitialize(void)
 	/* configure the high-resolution time/callout interface */
 	hrt_init();
 
+	/* configure the DMA allocator */
+	dma_alloc_init();
+
 	/* configure CPU load estimation */
 #ifdef CONFIG_SCHED_INSTRUMENTATION
 	cpuload_initialize_once();