Messages in this thread Patch in this message | | | Subject | [PATCH] Fix up SH DMAC code to correctly handle PVR DMA | From | Adrian McMenamin <> | Date | Tue, 02 Oct 2007 19:42:51 +0100 |
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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 <adrian@mcmen.demon.co.uk>
--- 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]); - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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