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AMS Sansa: dma-pl081.c: dma_enable_channel() Add step to clear pending interrupts from the previous operation. Add comments and make construction

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of the CH_CONTROL and CH_CONFIGURATION registers easier to follow.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@23725 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Jack Halpin 2009-11-23 19:44:13 +00:00
parent ae22ef13ed
commit f5b59cdf5e
1 changed files with 34 additions and 28 deletions
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62
firmware/target/arm/as3525/dma-pl081.c
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@ -63,41 +63,47 @@ void dma_enable_channel(int channel, void *src, void *dst, int peri,
{
dma_callback[channel] = callback;
int control = 0;
/* Clear any pending interrupts leftover from previous operation */
DMAC_INT_TC_CLEAR = (1<<channel);
DMAC_INT_ERR_CLEAR = (1<<channel);
DMAC_CH_SRC_ADDR(channel) = (int)src;
DMAC_CH_DST_ADDR(channel) = (int)dst;
DMAC_CH_LLI(channel) = 0; /* we use contigous memory, so don't use the LLI */
/* When LLI is 0 channel is disabled upon transfer completion */
DMAC_CH_LLI(channel) = 0;
/* specify address increment */
if(src_inc)
control |= (1<<26);
/* Channel Control Register */
DMAC_CH_CONTROL(channel) =
((1<<31) /* LLI triggers terminal count interrupt */
/* | (1<<30) */ /* cacheable = 1, non = 0 */
/* | (1<<29) */ /* bufferable = 1, non = 0 */
/* | (1<<28) */ /* privileged = 1, user = 0 */
| (dst_inc? (1<<27): 0) /* specify address increment */
| (src_inc? (1<<26): 0) /* specify address increment */
/* [25:24] */ /* undefined */
| (2<<21) /* dst width = word, 32bit */
| (2<<18) /* src width = word, 32bit */
/* OF uses transfers of 4 * 32 bits words on memory, i2sin, i2sout */
/* OF uses transfers of 8 * 32 bits words on SD */
| (nwords<<15) /* dst size */
| (nwords<<12) /* src size */
| ((size & 0x7ff)<<0)); /* transfer size */
if(dst_inc)
control |= (1<<27);
/* OF use transfers of 4 * 32 bits words on memory, i2sin, i2sout */
/* OF use transfers of 8 * 32 bits words on SD */
control |= (2<<21) | (2<<18); /* dst/src width = word, 32bit */
control |= (nwords<<15) | (nwords<<12); /* dst/src size */
control |= (size & 0x7ff); /* transfer size */
control |= (1<<31); /* current LLI is expected to trigger terminal count interrupt */
DMAC_CH_CONTROL(channel) = control;
/* we set the same peripheral as source and destination because we always
* use memory-to-peripheral or peripheral-to-memory transfers */
/* Channel Config Register */
DMAC_CH_CONFIGURATION(channel) =
(flow_controller<<11) /* flow controller is peripheral */
| (1<<15) /* terminal count interrupt mask */
| (1<<14) /* interrupt error mask */
| (peri<<6) /* dst peripheral */
| (peri<<1) /* src peripheral */
| (1<<0) /* enable channel */
;
/* [31:19] */ /* Read undefined. Write as zero */
/* (0<<18) */ /* Halt Bit */
/* (0<<17) */ /* Active Bit */
/* (0<<16) */ /* Lock Bit */
(1<<15) /* terminal count interrupt mask */
| (1<<14) /* interrupt error mask */
| (flow_controller<<11) /* flow controller is peripheral or SDMAC */
/* we set the same peripheral as source and destination because we
* always use memory-to-peripheral or peripheral-to-memory transfers */
| (peri<<6) /* dst peripheral */
| (peri<<1) /* src peripheral */
| (1<<0); /* enable channel */
}
/* isr */