V4L/DVB (6047): ivtv: Fix scatter/gather DMA timeouts

It turns out that the cx23415/6 DMA engine cannot do scatter/gather DMA
reliably. Every so often depending on the phase of the moon and your
hardware configuration the cx2341x DMA engine simply chokes on it and
you have to reboot to get it working again.

This change replaced the scatter/gather DMA by single transfers at a time,
where the driver is now responsible for DMA-ing each buffer.

UDMA is still done using scatter/gather DMA, that will be fixed soon.

Many thanks to Mark Bryars <mark.bryars@etvinteractive.com> for discovering
the link between scatter/gather and the DMA timeouts.

Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

drivers/media/video/ivtv/ivtv-driver.h

@@ -382,7 +382,6 @@ struct ivtv_mailbox_data {
 #define IVTV_F_I_RADIO_USER	   5 	/* The radio tuner is selected */
 #define IVTV_F_I_DIG_RST	   6 	/* Reset digitizer */
 #define IVTV_F_I_DEC_YUV	   7 	/* YUV instead of MPG is being decoded */
-#define IVTV_F_I_ENC_VBI	   8 	/* VBI DMA */
 #define IVTV_F_I_UPDATE_CC	   9  	/* CC should be updated */
 #define IVTV_F_I_UPDATE_WSS	   10 	/* WSS should be updated */
 #define IVTV_F_I_UPDATE_VPS	   11 	/* VPS should be updated */
@@ -405,7 +404,7 @@ struct ivtv_mailbox_data {
 #define IVTV_F_I_EV_VSYNC_ENABLED  31 	/* VSYNC event enabled */
 
 /* Scatter-Gather array element, used in DMA transfers */
-struct ivtv_SG_element {
+struct ivtv_sg_element {
 	u32 src;
 	u32 dst;
 	u32 size;
@@ -417,7 +416,7 @@ struct ivtv_user_dma {
 	struct page *map[IVTV_DMA_SG_OSD_ENT];
 
 	/* Base Dev SG Array for cx23415/6 */
-	struct ivtv_SG_element SGarray[IVTV_DMA_SG_OSD_ENT];
+	struct ivtv_sg_element SGarray[IVTV_DMA_SG_OSD_ENT];
 	dma_addr_t SG_handle;
 	int SG_length;
 
@@ -468,6 +467,10 @@ struct ivtv_stream {
 	int dma;		/* can be PCI_DMA_TODEVICE,
 				   PCI_DMA_FROMDEVICE or
 				   PCI_DMA_NONE */
+	u32 pending_offset;
+	u32 pending_backup;
+	u64 pending_pts;
+
 	u32 dma_offset;
 	u32 dma_backup;
 	u64 dma_pts;
@@ -493,10 +496,13 @@ struct ivtv_stream {
 	u16 dma_xfer_cnt;
 
 	/* Base Dev SG Array for cx23415/6 */
-	struct ivtv_SG_element *SGarray;
-	struct ivtv_SG_element *PIOarray;
-	dma_addr_t SG_handle;
-	int SG_length;
+	struct ivtv_sg_element *sg_pending;
+	struct ivtv_sg_element *sg_processing;
+	struct ivtv_sg_element *sg_dma;
+	dma_addr_t sg_handle;
+	int sg_pending_size;
+	int sg_processing_size;
+	int sg_processed;
 
 	/* SG List of Buffers */
 	struct scatterlist *SGlist;
@@ -637,7 +643,6 @@ struct vbi_info {
 	u32 enc_start, enc_size;
 	int fpi;
 	u32 frame;
-	u32 dma_offset;
 	u8 cc_data_odd[256];
 	u8 cc_data_even[256];
 	int cc_pos;
@@ -724,6 +729,7 @@ struct ivtv {
 	int cur_pio_stream;	/* index of stream doing PIO */
 	u32 dma_data_req_offset;
 	u32 dma_data_req_size;
+	int dma_retries;
 	int output_mode;        /* NONE, MPG, YUV, UDMA YUV, passthrough */
 	spinlock_t lock;        /* lock access to this struct */
 	int search_pack_header;