Macintosh-HW/BlueSCSI
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Merge pull request #94 from mactcp/Write-speed-tune

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Write speed tuning
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Eric Helgeson 2022-04-17 14:51:46 -05:00 committed by GitHub
commit a566c9bbb0
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1 changed files with 4 additions and 2 deletions
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src/BlueSCSI.cpp
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@ -935,14 +935,16 @@ void readDataLoop(uint32_t blockSize, byte* dstptr)
register gpio_reg_map *port_b = PBREG; register gpio_reg_map *port_b = PBREG;
register volatile uint32_t *port_a_idr = &(GPIOA->regs->IDR); register volatile uint32_t *port_a_idr = &(GPIOA->regs->IDR);
REQ_ON(); REQ_ON();
// Start of the do/while and WAIT are already aligned to 8 bytes. // Fastest alignment obtained by trial and error.
// Wait loop is within an 8 byte prefetch buffer.
asm("nop");
do { do {
WAIT_ACK_ACTIVE(); WAIT_ACK_ACTIVE();
uint32_t ret = port_b->IDR; uint32_t ret = port_b->IDR;
REQ_OFF(); REQ_OFF();
*dstptr++ = ~(ret >> 8); *dstptr++ = ~(ret >> 8);
// Move wait loop in to a single 8 byte prefetch buffer // Move wait loop in to a single 8 byte prefetch buffer
asm("nop.w;nop"); asm("nop;nop;nop");
WAIT_ACK_INACTIVE(); WAIT_ACK_INACTIVE();
REQ_ON(); REQ_ON();
// Extra 1 cycle delay // Extra 1 cycle delay