ASoC: rockchip: add support for sram audio buffer

This patch force the use of sram buffer for pcm buffer,
default is disabled.

Change-Id: I2e6936e1071347f767c67066126b22e39fb477c5
Signed-off-by: Sugar Zhang <sugar.zhang@rock-chips.com>

sound/core/memalloc.c

@@ -192,6 +192,9 @@ int snd_dma_alloc_pages(int type, struct device *device, size_t size,
 		snd_malloc_dev_iram(dmab, size);
 		if (dmab->area)
 			break;
+#ifdef CONFIG_SND_SOC_ROCKCHIP_FORCE_SRAM
+		break;
+#endif
 		/* Internal memory might have limited size and no enough space,
 		 * so if we fail to malloc, try to fetch memory traditionally.
 		 */

sound/soc/rockchip/Kconfig

@@ -6,6 +6,13 @@ config SND_SOC_ROCKCHIP
 	  the Rockchip SoCs' Audio interfaces. You will also need to
 	  select the audio interfaces to support below.
 
+config SND_SOC_ROCKCHIP_FORCE_SRAM
+	bool "Rockchip force using sram buffer"
+	def_bool n
+	help
+	  Say Y if you want to force using sram buffer for pcm buffer,
+	  but the sram size is limited.
+
 config SND_SOC_ROCKCHIP_I2S
 	tristate "Rockchip I2S Device Driver"
 	depends on CLKDEV_LOOKUP && SND_SOC_ROCKCHIP

sound/soc/soc-generic-dmaengine-pcm.c

@@ -267,6 +267,9 @@ static int dmaengine_pcm_new(struct snd_soc_pcm_runtime *rtd)
 		max_buffer_size = SIZE_MAX;
 	}
 
+#ifdef CONFIG_SND_SOC_ROCKCHIP_FORCE_SRAM
+	prealloc_buffer_size = 32 * 1024;
+#endif
 
 	for (i = SNDRV_PCM_STREAM_PLAYBACK; i <= SNDRV_PCM_STREAM_CAPTURE; i++) {
 		substream = rtd->pcm->streams[i].substream;