Followup to HAL optimizations and delays

- Cleanups, fixes for Due HAL code.
- TC_IER is write-only. Use TC_IMR to test ISR state.

Marlin/src/HAL/Delay.h

 #ifndef MARLIN_DELAY_H
 #define MARLIN_DELAY_H
 
+#include "../core/macros.h"
+
 #if defined(__arm__) || defined(__thumb__)
 
   /* https://blueprints.launchpad.net/gcc-arm-embedded/+spec/delay-cycles */

Marlin/src/HAL/HAL_DUE/HAL_spi_Due.cpp

 
     /* The software SPI routine */
     __asm__ __volatile__(
-      ".syntax unified" "\n\t" // is to prevent CM0,CM1 non-unified syntax
+      A(".syntax unified") // is to prevent CM0,CM1 non-unified syntax
 
       /* Bit 7 */
       A("ubfx %[idx],%[txval],#7,#1")                      /* Place bit 7 in bit 0 of idx*/
 
     /* The software SPI routine */
     __asm__ __volatile__(
-      ".syntax unified" "\n\t" // is to prevent CM0,CM1 non-unified syntax
+      A(".syntax unified") // is to prevent CM0,CM1 non-unified syntax
 
       /* bit 7 */
       A("str %[sck_mask],[%[sck_port]]")           /* SODR */
 
     /* The software SPI routine */
     __asm__ __volatile__(
-      ".syntax unified" "\n\t" // is to prevent CM0,CM1 non-unified syntax
+      A(".syntax unified") // is to prevent CM0,CM1 non-unified syntax
 
       L("loop%=")
       A("ldrb.w %[txval], [%[ptr]], #1")                   /* Load value to send, increment buffer */
 
     /* The software SPI routine */
     __asm__ __volatile__(
-      ".syntax unified" "\n\t" // is to prevent CM0,CM1 non-unified syntax
+      A(".syntax unified")                  // is to prevent CM0,CM1 non-unified syntax
 
       L("loop%=")
 

Marlin/src/HAL/HAL_DUE/HAL_timers_Due.cpp

 
 bool HAL_timer_interrupt_enabled(const uint8_t timer_num) {
   const tTimerConfig * const pConfig = &TimerConfig[timer_num];
-  return pConfig->pTimerRegs->TC_CHANNEL[pConfig->channel].TC_IER == TC_IER_CPCS;
+  return (pConfig->pTimerRegs->TC_CHANNEL[pConfig->channel].TC_IMR & TC_IMR_CPCS) != 0;
 }
 
-#if 0
-  void HAL_timer_set_compare(const uint8_t timer_num, const uint32_t compare) {
-    const tTimerConfig * const pConfig = &TimerConfig[timer_num];
-    TC_SetRC(pConfig->pTimerRegs, pConfig->channel, compare);
-  }
-
-  void HAL_timer_isr_prologue(const uint8_t timer_num) {
-    const tTimerConfig * const pConfig = &TimerConfig[timer_num];
-    TC_GetStatus(pConfig->pTimerRegs, pConfig->channel);
-  }
-#endif
-
 #endif // ARDUINO_ARCH_SAM

Marlin/src/HAL/HAL_DUE/u8g_com_HAL_DUE_st7920_sw_spi.cpp

 #include <U8glib.h>
 #include <Arduino.h>
 #include "../../core/macros.h"
+#include "../Delay.h"
 
 void u8g_SetPIOutput_DUE(u8g_t *u8g, uint8_t pin_index) {
    PIO_Configure(g_APinDescription[u8g->pin_list[pin_index]].pPort, PIO_OUTPUT_1,
   else port->PIO_CODR = mask;
 }
 
-void __delay_4cycles(uint32_t cy) __attribute__ ((weak));
-
-FORCE_INLINE void __delay_4cycles(uint32_t cy) { // +1 cycle
-  #if ARCH_PIPELINE_RELOAD_CYCLES<2
-    #define EXTRA_NOP_CYCLES "nop"
-  #else
-    #define EXTRA_NOP_CYCLES ""
-  #endif
-
-  __asm__ __volatile__(
-    ".syntax unified" "\n\t" // is to prevent CM0,CM1 non-unified syntax
-
-    L("loop%=")
-    A("subs %[cnt],#1")
-    A(EXTRA_NOP_CYCLES)
-    A("bne loop%=")
-    : [cnt]"+r"(cy) // output: +r means input+output
-    : // input:
-    : "cc" // clobbers:
-  );
-}
-
 Pio *SCK_pPio, *MOSI_pPio;
 uint32_t SCK_dwMask, MOSI_dwMask;
 
       MOSI_pPio->PIO_SODR = MOSI_dwMask;
     else
       MOSI_pPio->PIO_CODR = MOSI_dwMask;
-    __delay_4cycles(1);
+    DELAY_NS(48);
     SCK_pPio->PIO_SODR = SCK_dwMask;
-    __delay_4cycles(19); // 16 dead, 17 garbage, 18/0 900kHz, 19/1 825k, 20/1 800k, 21/2 725KHz
+    DELAY_NS(905); // 762 dead, 810 garbage, 858/0 900kHz, 905/1 825k, 953/1 800k, 1000/2 725KHz
     val <<= 1;
     SCK_pPio->PIO_CODR = SCK_dwMask;
   }
        /* data */
       spiSend_sw_DUE(0x0FA);
 
-    for (i = 0; i < 4; i++)   // give the controller some time to process the data
-      u8g_10MicroDelay();     // 2 is bad, 3 is OK, 4 is safe
+    DELAY_US(40); // give the controller some time to process the data: 20 is bad, 30 is OK, 40 is safe
   }
 
   spiSend_sw_DUE(val & 0x0F0);

Marlin/src/HAL/HAL_LPC1768/include/Wire.cpp

   // perform blocking read into buffer
   I2C_M_SETUP_Type transferMCfg;
   transferMCfg.sl_addr7bit = address >> 1; // not sure about the right shift
-	transferMCfg.tx_data = NULL;
-	transferMCfg.tx_length = 0;
-	transferMCfg.rx_data = rxBuffer;
-	transferMCfg.rx_length = quantity;
-	transferMCfg.retransmissions_max = 3;
-	I2C_MasterTransferData(I2CDEV_M, &transferMCfg, I2C_TRANSFER_POLLING);
+  transferMCfg.tx_data = NULL;
+  transferMCfg.tx_length = 0;
+  transferMCfg.rx_data = rxBuffer;
+  transferMCfg.rx_length = quantity;
+  transferMCfg.retransmissions_max = 3;
+  I2C_MasterTransferData(I2CDEV_M, &transferMCfg, I2C_TRANSFER_POLLING);
 
   // set rx buffer iterator vars
   rxBufferIndex = 0;
   // transmit buffer (blocking)
   I2C_M_SETUP_Type transferMCfg;
   transferMCfg.sl_addr7bit = txAddress >> 1; // not sure about the right shift
-	transferMCfg.tx_data = txBuffer;
-	transferMCfg.tx_length = txBufferLength;
-	transferMCfg.rx_data = NULL;
-	transferMCfg.rx_length = 0;
-	transferMCfg.retransmissions_max = 3;
+  transferMCfg.tx_data = txBuffer;
+  transferMCfg.tx_length = txBufferLength;
+  transferMCfg.rx_data = NULL;
+  transferMCfg.rx_length = 0;
+  transferMCfg.retransmissions_max = 3;
   Status status = I2C_MasterTransferData(I2CDEV_M, &transferMCfg, I2C_TRANSFER_POLLING);
 
   // reset tx buffer iterator vars

Marlin/src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_st7920_hw_spi.cpp

   //#include "Configuration.h"
 
   #include <U8glib.h>
+  #include "../Delay.h"
 
   #define SPI_FULL_SPEED 0
   #define SPI_HALF_SPEED 1
          /* data */
         spiSend(0x0FA);
 
-      for( i = 0; i < 4; i++ )   // give the controller some time to process the data
-        u8g_10MicroDelay();      // 2 is bad, 3 is OK, 4 is safe
+      DELAY_US(40); // give the controller some time to process the data: 20 is bad, 30 is OK, 40 is safe
     }
 
     spiSend(val & 0x0F0);

Marlin/src/HAL/HAL_LPC1768/u8g_com_HAL_LPC1768_st7920_sw_spi.cpp

 
   #include <U8glib.h>
   #include "SoftwareSPI.h"
+  #include "../Delay.h"
 
   #define SPI_SPEED 3  // About 1 MHz
 
          /* data */
          swSpiTransfer(0x0FA, SPI_speed, SCK_pin_ST7920_HAL, -1, MOSI_pin_ST7920_HAL_HAL);
 
-      for( i = 0; i < 4; i++ )   // give the controller some time to process the data
-        u8g_10MicroDelay();      // 2 is bad, 3 is OK, 4 is safe
+      DELAY_US(40); // give the controller some time to process the data: 20 is bad, 30 is OK, 40 is safe
     }
 
     swSpiTransfer(val & 0x0F0, SPI_speed, SCK_pin_ST7920_HAL, -1, MOSI_pin_ST7920_HAL_HAL);

Marlin/src/lcd/dogm/ultralcd_st7920_u8glib_rrd_AVR.cpp

 #if DOGM_SPI_DELAY_US > 0
   #define U8G_DELAY() DELAY_US(DOGM_SPI_DELAY_US)
 #else
-  #define U8G_DELAY() u8g_10MicroDelay()
+  #define U8G_DELAY() DELAY_US(10)
 #endif
 
 #define ST7920_CS()              { WRITE(ST7920_CS_PIN,1); U8G_DELAY(); }