Merge pull request adafruit#414 from tannewt/new_opt

Turn on -Os and tweak neopixel for new code output.

Author: dhalbert

ports/atmel-samd/Makefile

@@ -85,7 +85,7 @@ CFLAGS = -Os -DNDEBUG
 endif
 
 ifeq ($(CHIP_FAMILY), samd51)
-CFLAGS = -O2 -DNDEBUG
+CFLAGS = -Os -DNDEBUG
 endif
 
 #Debugging/Optimization

ports/atmel-samd/common-hal/neopixel_write/__init__.c

@@ -32,18 +32,17 @@
 #include "tick.h"
 
 #ifdef SAMD51
-static inline void delay_cycles(uint8_t cycles) {
- uint32_t start = SysTick->VAL;
- uint32_t stop = start - cycles;
- if (start < cycles) {
-  stop = 0xffffff + start - cycles;
-  while (SysTick->VAL < start || SysTick->VAL > stop) {}
- } else {
- // Make sure the systick value is between start and stop in case it
- // wraps around before we read its value less than stop.
- while (SysTick->VAL > stop && SysTick->VAL <= start) {}
+// This magical macro makes sure the delay isn't optimized out and is the
+// minimal three instructions.
+#define delay_cycles(cycles) \
+{ \
+ uint32_t t; \
+ asm volatile ( \
+  "movs %[t], %[c]\n\t" \
+ "loop%=:\n\t" \
+ "subs	%[t], #1\n\t" \
+ "bne.n loop%=" : [t] "=r"(t) : [c] "I" (cycles)); \
  }
-}
 #endif
 
 uint64_t next_start_tick_ms = 0;
@@ -88,7 +87,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
  asm("nop; nop;");
  #endif
  #ifdef SAMD51
- delay_cycles(18);
+ delay_cycles(3);
  #endif
  if(p & bitMask) {
  // This is the high delay unique to a one bit.
@@ -97,7 +96,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
  asm("nop; nop; nop; nop; nop; nop; nop;");
  #endif
  #ifdef SAMD51
- delay_cycles(25);
+ delay_cycles(11);
  #endif
  *clr = pinMask;
  } else {
@@ -108,7 +107,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
  asm("nop; nop;");
  #endif
  #ifdef SAMD51
- delay_cycles(25);
+ delay_cycles(3);
  #endif
  }
  if((bitMask >>= 1) != 0) {
@@ -119,7 +118,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
  asm("nop; nop; nop; nop; nop;");
  #endif
  #ifdef SAMD51
- delay_cycles(44);
+ delay_cycles(20);
  #endif
  } else {
  if(ptr >= end) break;
@@ -130,7 +129,7 @@ void common_hal_neopixel_write(const digitalio_digitalinout_obj_t* digitalinout,
  // above operations take.
  // For the SK6812 its 0.6us +- 0.15us
  #ifdef SAMD51
- delay_cycles(50);
+ delay_cycles(15);
  #endif
  }
  }

ports/atmel-samd/usb_mass_storage.c

@@ -259,6 +259,9 @@ int32_t usb_msc_xfer_done(uint8_t lun) {
  if (active_read) {
  active_addr += 1;
  active_nblocks--;
+ if (active_nblocks == 0) {
+ active_read = false;
+ }
  }
 
  if (active_write) {
@@ -272,10 +275,6 @@ int32_t usb_msc_xfer_done(uint8_t lun) {
 // The start_read callback begins a read transaction which we accept but delay our response until the "main thread" calls usb_msc_background. Once it does, we read immediately from the drive into our cache and trigger the USB DMA to output the sector. Once the sector is transmitted, xfer_done will be called.
 void usb_msc_background(void) {
  if (active_read && !usb_busy) {
- if (active_nblocks == 0) {
- active_read = false;
- return;
- }
  fs_user_mount_t * vfs = get_vfs(active_lun);
  disk_read(vfs, sector_buffer, active_addr, 1);
  // TODO(tannewt): Check the read result.