This patch fixes up SH DMAC code to correctly handle channel 2 DMA on
the Dreamcast.
Points to note:
* Currently the comments say that dar must be set - this appears to be
incorrect
* Currently the code uses calc_xmit_shift(chan) though that fuction does
not appear to work - this code relies on a division by 32 before the
xfer function is called
* Currently the code supports reading and writing, but the hardware only
supports writing
Signed-off by Adrian McMenamin <[email protected]>
--- arch/sh/drivers/dma/dma-sh.c 2007/09/22 18:34:42 1.1
+++ arch/sh/drivers/dma/dma-sh.c 2007/09/22 18:37:28 1.2
@@ -150,6 +150,13 @@ static void sh_dmac_disable_dma(struct d
static int sh_dmac_xfer_dma(struct dma_channel *chan)
{
+ /* Handle Dreamcast PVR cascade */
+ if (mach_is_dreamcast() && chan->chan == PVR2_CASCADE_CHAN)
+ {
+ ctrl_outl(chan->sar, SAR[chan->chan]);
+ ctrl_outl(chan->count, DMATCR[chan->chan]);
+ return 0;
+ }
/*
* If we haven't pre-configured the channel with special flags, use
* the defaults.
@@ -159,26 +166,9 @@ static int sh_dmac_xfer_dma(struct dma_c
sh_dmac_disable_dma(chan);
- /*
- * Single-address mode usage note!
- *
- * It's important that we don't accidentally write any value to SAR/DAR
- * (this includes 0) that hasn't been directly specified by the user if
- * we're in single-address mode.
- *
- * In this case, only one address can be defined, anything else will
- * result in a DMA address error interrupt (at least on the SH-4),
- * which will subsequently halt the transfer.
- *
- * Channel 2 on the Dreamcast is a special case, as this is used for
- * cascading to the PVR2 DMAC. In this case, we still need to write
- * SAR and DAR, regardless of value, in order for cascading to work.
- */
- if (chan->sar || (mach_is_dreamcast() &&
- chan->chan == PVR2_CASCADE_CHAN))
+ if (chan->sar)
ctrl_outl(chan->sar, SAR[chan->chan]);
- if (chan->dar || (mach_is_dreamcast() &&
- chan->chan == PVR2_CASCADE_CHAN))
+ if (chan->dar)
ctrl_outl(chan->dar, DAR[chan->chan]);
ctrl_outl(chan->count >> calc_xmit_shift(chan), DMATCR[chan->chan]);
-
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