V4L/DVB (3293): Added digital support for cx88 (cx88-alsa)

- This module is co-authored by  Ricardo Cerqueira <v4l@cerqueira.org>.

- Added digital audio support for cx88-based boards that have function
  01 enabled. These boards can be identified by having PCI id 1471:8801
  or 1471:8811.

- Increased DMA buffer from 512 to 4096 seems to fix audio distortion.

- Existing audio DMA uses conflict with cx88-alsa. Should be disabled when
  cx88-alsa module is compiled.
Signed-off-by: Ricardo Cerqueira <v4l@cerqueira.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@brturbo.com.br>

drivers/media/video/cx88/Kconfig

@@ -29,6 +29,21 @@ config VIDEO_CX88_DVB
 	  You must also select one or more DVB/ATSC demodulators.
 	  If you are unsure which you need, choose all of them.
 
+config VIDEO_CX88_ALSA
+	tristate "ALSA DMA audio support"
+	depends on VIDEO_CX88 && SND
+	select SND_PCM_OSS
+	---help---
+	  This is a video4linux driver for direct (DMA) audio on
+	  Conexant 2388x based TV cards.
+	  It only works with boards with function 01 enabled.
+	  To check if your board supports, use lspci -n.
+	  If supported, you should see 1471:8801 or 1471:8811
+	  PCI device.
+
+	  To compile this driver as a module, choose M here: the
+	  module will be called cx88-alsa.
+
 config VIDEO_CX88_DVB_ALL_FRONTENDS
 	bool "Build all supported frontends for cx2388x based TV cards"
 	default y

drivers/media/video/cx88/cx88-core.c

@@ -238,9 +238,9 @@ cx88_free_buffer(struct pci_dev *pci, struct cx88_buffer *buf)
  *    channel  22    (u video)  -  2.0k
  *    channel  23    (v video)  -  2.0k
  *    channel  24    (vbi)      -  4.0k
- *    channels 25+26 (audio)    -  0.5k
+ *    channels 25+26 (audio)    -  4.0k
  *    channel  28    (mpeg)     -  4.0k
- *    TOTAL                     = 25.5k
+ *    TOTAL                     = 29.0k
  *
  * Every channel has 160 bytes control data (64 bytes instruction
  * queue and 6 CDT entries), which is close to 2k total.
@@ -306,7 +306,7 @@ struct sram_channel cx88_sram_channels[] = {
 		.ctrl_start = 0x180680,
 		.cdt        = 0x180680 + 64,
 		.fifo_start = 0x185400,
-		.fifo_size  = 0x000200,
+		.fifo_size  = 0x001000,
 		.ptr1_reg   = MO_DMA25_PTR1,
 		.ptr2_reg   = MO_DMA25_PTR2,
 		.cnt1_reg   = MO_DMA25_CNT1,
@@ -318,7 +318,7 @@ struct sram_channel cx88_sram_channels[] = {
 		.ctrl_start = 0x180720,
 		.cdt        = 0x180680 + 64,  /* same as audio IN */
 		.fifo_start = 0x185400,       /* same as audio IN */
-		.fifo_size  = 0x000200,       /* same as audio IN */
+		.fifo_size  = 0x001000,       /* same as audio IN */
 		.ptr1_reg   = MO_DMA26_PTR1,
 		.ptr2_reg   = MO_DMA26_PTR2,
 		.cnt1_reg   = MO_DMA26_CNT1,
@@ -329,7 +329,7 @@ struct sram_channel cx88_sram_channels[] = {
 		.cmds_start = 0x180200,
 		.ctrl_start = 0x1807C0,
 		.cdt        = 0x1807C0 + 64,
-		.fifo_start = 0x185600,
+		.fifo_start = 0x186400,
 		.fifo_size  = 0x001000,
 		.ptr1_reg   = MO_DMA28_PTR1,
 		.ptr2_reg   = MO_DMA28_PTR2,
@@ -795,7 +795,6 @@ int cx88_start_audio_dma(struct cx88_core *core)
 
 	/* start dma */
 	cx_write(MO_AUD_DMACNTRL, 0x0003); /* Up and Down fifo enable */
-
 	return 0;
 }
 

drivers/media/video/cx88/cx88-tvaudio.c

@@ -132,10 +132,14 @@ static void set_audio_finish(struct cx88_core *core, u32 ctl)
 {
 	u32 volume;
 
+#ifndef USING_CX88_ALSA
 	/* restart dma; This avoids buzz in NICAM and is good in others  */
 	cx88_stop_audio_dma(core);
+#endif
 	cx_write(AUD_RATE_THRES_DMD, 0x000000C0);
+#ifndef USING_CX88_ALSA
 	cx88_start_audio_dma(core);
+#endif
 
 	if (cx88_boards[core->board].blackbird) {
 		/* sets sound input from external adc */