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cope with I$ miss on teensy #405

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cope with I$ miss on teensy #405

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34 changes: 29 additions & 5 deletions Adafruit_NeoPixel.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,13 @@

#include "Adafruit_NeoPixel.h"

#define barrier() __asm__ __volatile__ ("" ::: "memory")

#undef REPRODUCE_TEENSY_TIMING
#ifdef REPRODUCE_TEENSY_TIMING
#include "imxrt.h"
#endif

#if defined(TARGET_LPC1768)
#include <time.h>
#endif
Expand Down Expand Up @@ -1912,16 +1919,32 @@ void Adafruit_NeoPixel::show(void) {
ARM_DEMCR |= ARM_DEMCR_TRCENA;
ARM_DWT_CTRL |= ARM_DWT_CTRL_CYCCNTENA;

#ifdef REPRODUCE_TEENSY_TIMING
// reproducer for the timing issue
{
static uint8_t ct;

//if (!(ct & 1)) {
if (true) {
asm("dsb");
asm("isb");
SCB_CACHE_ICIALLU = 0UL;
asm("dsb");
asm("isb");
}
ct++;
}
#endif

#if defined(NEO_KHZ400) // 800 KHz check needed only if 400 KHz support enabled
if (is800KHz) {
#endif
cyc = ARM_DWT_CYCCNT + CYCLES_800;
cyc = ARM_DWT_CYCCNT; // make sure it's initialised..
while (p < end) {
pix = *p++;
for (mask = 0x80; mask; mask >>= 1) {
while (ARM_DWT_CYCCNT - cyc < CYCLES_800)
;
cyc = ARM_DWT_CYCCNT;
barrier();
*set = msk;
if (pix & mask) {
while (ARM_DWT_CYCCNT - cyc < CYCLES_800_T1H)
Expand All @@ -1931,10 +1954,11 @@ void Adafruit_NeoPixel::show(void) {
;
}
*clr = msk;
barrier();
while (ARM_DWT_CYCCNT - cyc < CYCLES_800)
;
}
}
while (ARM_DWT_CYCCNT - cyc < CYCLES_800)
;
#if defined(NEO_KHZ400)
} else { // 400 kHz bitstream
cyc = ARM_DWT_CYCCNT + CYCLES_400;
Expand Down
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