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Update DMA registers correctly. Update read_count

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Previously, the channel_count and channel_addr registers were
incremented/decremented using read_count. However, read_bytes can be
reassigned (from the original bytes assosiated with channel_count) to
len. When do_write is performed with len less than available data,
read_bytes is reduced to len, but read_count is still referring to the
entire data, making subsequent writes restarting at the initial address.
This commit is contained in:
Ernest Wong 2017-11-26 20:07:39 +13:00 committed by Fabian
parent 42c5ddc1bd
commit 60ca5c04cd
1 changed files with 5 additions and 9 deletions
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14
src/dma.js
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@ -354,25 +354,21 @@ DMA.prototype.do_read = function(buffer, start, len, channel, fn)
DMA.prototype.do_write = function(buffer, start, len, channel, fn)
{
var read_count = (this.channel_count[channel] + 1) & 0xFFFF,
read_bytes = read_count,
bytes_per_count = channel >= 5 ? 2 : 1,
read_bytes = read_count * bytes_per_count,
addr = this.address_get_8bit(channel),
unfinished = false,
want_more = false,
autoinit = this.channel_mode[channel] & 0x10;
if(channel >= 5)
{
// convert word count to byte count
read_bytes *= 2;
}
dbg_log("DMA write channel " + channel, LOG_DMA);
dbg_log("to " + h(addr) + " len " + h(read_bytes), LOG_DMA);
if(len < read_bytes)
{
dbg_log("DMA should read more than provided", LOG_DMA);
read_bytes = len;
read_count = Math.floor(len / bytes_per_count);
read_bytes = read_count * bytes_per_count;
unfinished = true;
}
else if(len > read_bytes)
@ -406,7 +402,7 @@ DMA.prototype.do_write = function(buffer, start, len, channel, fn)
if(want_more && autoinit)
{
dbg_log("DMA continuing from start", LOG_DMA);
this.do_write(buffer, start, len - read_bytes, channel, fn);
this.do_write(buffer, start + read_bytes, len - read_bytes, channel, fn);
}
else
{