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-rw-r--r--sound/pci/es1938.c27
1 files changed, 25 insertions, 2 deletions
diff --git a/sound/pci/es1938.c b/sound/pci/es1938.c
index fbe3da73eaff..1a314fa99c45 100644
--- a/sound/pci/es1938.c
+++ b/sound/pci/es1938.c
@@ -226,6 +226,7 @@ struct es1938 {
unsigned int dma2_start;
unsigned int dma1_shift;
unsigned int dma2_shift;
+ unsigned int last_capture_dmaaddr;
unsigned int active;
spinlock_t reg_lock;
@@ -528,6 +529,7 @@ static void snd_es1938_capture_setdma(struct es1938 *chip)
outb(1, SLDM_REG(chip, DMAMASK));
outb(0x14, SLDM_REG(chip, DMAMODE));
outl(chip->dma1_start, SLDM_REG(chip, DMAADDR));
+ chip->last_capture_dmaaddr = chip->dma1_start;
outw(chip->dma1_size - 1, SLDM_REG(chip, DMACOUNT));
/* 3. Unmask DMA */
outb(0, SLDM_REG(chip, DMAMASK));
@@ -769,19 +771,40 @@ static int snd_es1938_playback_prepare(struct snd_pcm_substream *substream)
return -EINVAL;
}
+/* during the incrementing of dma counters the DMA register reads sometimes
+ returns garbage. To ensure a valid hw pointer, the following checks which
+ should be very unlikely to fail are used:
+ - is the current DMA address in the valid DMA range ?
+ - is the sum of DMA address and DMA counter pointing to the last DMA byte ?
+ One can argue this could differ by one byte depending on which register is
+ updated first, so the implementation below allows for that.
+*/
static snd_pcm_uframes_t snd_es1938_capture_pointer(struct snd_pcm_substream *substream)
{
struct es1938 *chip = snd_pcm_substream_chip(substream);
size_t ptr;
+#if 0
size_t old, new;
-#if 1
/* This stuff is *needed*, don't ask why - AB */
old = inw(SLDM_REG(chip, DMACOUNT));
while ((new = inw(SLDM_REG(chip, DMACOUNT))) != old)
old = new;
ptr = chip->dma1_size - 1 - new;
#else
- ptr = inl(SLDM_REG(chip, DMAADDR)) - chip->dma1_start;
+ size_t count;
+ unsigned int diff;
+
+ ptr = inl(SLDM_REG(chip, DMAADDR));
+ count = inw(SLDM_REG(chip, DMACOUNT));
+ diff = chip->dma1_start + chip->dma1_size - ptr - count;
+
+ if (diff > 3 || ptr < chip->dma1_start
+ || ptr >= chip->dma1_start+chip->dma1_size)
+ ptr = chip->last_capture_dmaaddr; /* bad, use last saved */
+ else
+ chip->last_capture_dmaaddr = ptr; /* good, remember it */
+
+ ptr -= chip->dma1_start;
#endif
return ptr >> chip->dma1_shift;
}
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