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>

1 files changed, 36 insertions, 27 deletions

diff --git a/drivers/media/video/ivtv/ivtv-queue.c b/drivers/media/video/ivtv/ivtv-queue.c
index bff75aeee0a0..d9a1478ca1f7 100644
--- a/drivers/media/video/ivtv/ivtv-queue.c
+++ b/drivers/media/video/ivtv/ivtv-queue.c
@@ -195,7 +195,7 @@ void ivtv_flush_queues(struct ivtv_stream *s)
 int ivtv_stream_alloc(struct ivtv_stream *s)
 {
         struct ivtv *itv = s->itv;
-        int SGsize = sizeof(struct ivtv_SG_element) * s->buffers;
+        int SGsize = sizeof(struct ivtv_sg_element) * s->buffers;
         int i;
 
         if (s->buffers == 0)
@@ -205,27 +205,33 @@ int ivtv_stream_alloc(struct ivtv_stream *s)
                 s->dma != PCI_DMA_NONE ? "DMA " : "",
                 s->name, s->buffers, s->buf_size, s->buffers * s->buf_size / 1024);
 
-        if (ivtv_might_use_pio(s)) {
-                s->PIOarray = (struct ivtv_SG_element *)kzalloc(SGsize, GFP_KERNEL);
-                if (s->PIOarray == NULL) {
-                        IVTV_ERR("Could not allocate PIOarray for %s stream\n", s->name);
-                        return -ENOMEM;
-                }
+        s->sg_pending = (struct ivtv_sg_element *)kzalloc(SGsize, GFP_KERNEL);
+        if (s->sg_pending == NULL) {
+                IVTV_ERR("Could not allocate sg_pending for %s stream\n", s->name);
+                return -ENOMEM;
         }
+        s->sg_pending_size = 0;
 
-        /* Allocate DMA SG Arrays */
-        s->SGarray = (struct ivtv_SG_element *)kzalloc(SGsize, GFP_KERNEL);
-        if (s->SGarray == NULL) {
-                IVTV_ERR("Could not allocate SGarray for %s stream\n", s->name);
-                if (ivtv_might_use_pio(s)) {
-                        kfree(s->PIOarray);
-                        s->PIOarray = NULL;
-                }
+        s->sg_processing = (struct ivtv_sg_element *)kzalloc(SGsize, GFP_KERNEL);
+        if (s->sg_processing == NULL) {
+                IVTV_ERR("Could not allocate sg_processing for %s stream\n", s->name);
+                kfree(s->sg_pending);
+                s->sg_pending = NULL;
+                return -ENOMEM;
+        }
+        s->sg_processing_size = 0;
+
+        s->sg_dma = (struct ivtv_sg_element *)kzalloc(sizeof(struct ivtv_sg_element), GFP_KERNEL);
+        if (s->sg_dma == NULL) {
+                IVTV_ERR("Could not allocate sg_dma for %s stream\n", s->name);
+                kfree(s->sg_pending);
+                s->sg_pending = NULL;
+                kfree(s->sg_processing);
+                s->sg_processing = NULL;
                 return -ENOMEM;
         }
-        s->SG_length = 0;
         if (ivtv_might_use_dma(s)) {
-                s->SG_handle = pci_map_single(itv->dev, s->SGarray, SGsize, s->dma);
+                s->sg_handle = pci_map_single(itv->dev, s->sg_dma, sizeof(struct ivtv_sg_element), s->dma);
                 ivtv_stream_sync_for_cpu(s);
         }
 
@@ -272,16 +278,19 @@ void ivtv_stream_free(struct ivtv_stream *s)
         }
 
         /* Free SG Array/Lists */
-        if (s->SGarray != NULL) {
-                if (s->SG_handle != IVTV_DMA_UNMAPPED) {
-                        pci_unmap_single(s->itv->dev, s->SG_handle,
-                                 sizeof(struct ivtv_SG_element) * s->buffers, PCI_DMA_TODEVICE);
-                        s->SG_handle = IVTV_DMA_UNMAPPED;
+        if (s->sg_dma != NULL) {
+                if (s->sg_handle != IVTV_DMA_UNMAPPED) {
+                        pci_unmap_single(s->itv->dev, s->sg_handle,
+                                 sizeof(struct ivtv_sg_element), PCI_DMA_TODEVICE);
+                        s->sg_handle = IVTV_DMA_UNMAPPED;
                 }
-                kfree(s->SGarray);
-                kfree(s->PIOarray);
-                s->PIOarray = NULL;
-                s->SGarray = NULL;
-                s->SG_length = 0;
+                kfree(s->sg_pending);
+                kfree(s->sg_processing);
+                kfree(s->sg_dma);
+                s->sg_pending = NULL;
+                s->sg_processing = NULL;
+                s->sg_dma = NULL;
+                s->sg_pending_size = 0;
+                s->sg_processing_size = 0;
         }
 }