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Hand assemble to get alignment

pull/9812/head
Kevin Bracey 2019-02-25 13:48:08 +02:00
parent 66dea08c0f
commit 91b22f8bf3
1 changed files with 19 additions and 48 deletions
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67
platform/mbed_wait_api_no_rtos.c
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@ -16,6 +16,7 @@
*/
#include "cmsis.h"
#include "platform/mbed_toolchain.h"
#include "platform/mbed_wait_api.h"
// This implementation of the wait functions will be compiled only
@ -47,11 +48,11 @@ void wait_us(int us)
#ifdef __CORTEX_M
#if (__CORTEX_M == 0 && !defined __CM0PLUS_REV) || __CORTEX_M == 1
// Cortex-M0 and Cortex-M1 take 7 cycles per iteration - SUBS = 1, 2xNOP = 2, BCS = 3
// Cortex-M0 and Cortex-M1 take 6 cycles per iteration - SUBS = 1, 2xNOP = 2, BCS = 3
#define LOOP_SCALER 6000
#elif (__CORTEX_M == 0 && defined __CM0PLUS_REV) || __CORTEX_M == 3 || __CORTEX_M == 4 || \
__CORTEX_M == 23 || __CORTEX_M == 33
// Cortex-M0+, M3, M4, M23 and M33 take 6 cycles per iteration - SUBS = 1, 3xNOP = 2, BCS = 2
// Cortex-M0+, M3, M4, M23 and M33 take 5 cycles per iteration - SUBS = 1, 2xNOP = 2, BCS = 2
// TODO - check M33
#define LOOP_SCALER 5000
#elif __CORTEX_M == 7
@ -76,52 +77,22 @@ void wait_us(int us)
*/
#ifdef LOOP_SCALER
// *INDENT-OFF*
#ifdef __CC_ARM /* ARMC5 */
__asm static void delay_loop(uint32_t count)
{
1
SUBS a1, a1, #1
NOP
NOP
BCS %BT1
BX lr
}
#elif defined (__ICCARM__)
static void delay_loop(uint32_t count)
{
__asm volatile(
"loop: \n"
" SUBS %0, %0, #1 \n"
" NOP\n"
" NOP\n"
" BCS.n loop\n"
: "+r" (count)
:
: "cc"
);
}
#else // GCC or ARMC6
static void delay_loop(uint32_t count)
{
__asm__ volatile (
"%=:\n\t"
/* Only GCC insists on non-UAL assembly for Thumb v1 */
#if !defined(__ARMCC_VERSION) && defined(__thumb__) && !defined(__thumb2__)
"SUB %0, #1\n\t"
#else
"SUBS %0, %0, #1\n\t"
#endif
"NOP\n\t"
"NOP\n\t"
"BCS %=b\n\t"
: "+l" (count)
:
: "cc"
);
}
#endif
// *INDENT-ON*
/* Timing seems to depend on alignment, and toolchains do not support aligning
* functions well. So sidestep that by hand-assembling the code. Also avoids
* the hassle of handling multiple toolchains with different assembler
* syntax.
*/
MBED_ALIGN(8)
static const uint16_t delay_loop_code[] = {
0x1E40, // SUBS R0,R0,#1
0xBF00, // NOP
0xBF00, // NOP
0xD2FB, // BCS .-3 (0x00 would be .+2, so 0xFB = -5 = .-3)
0x4770 // BX LR
};
/* Take the address of the code, set LSB to indicate Thumb, and cast to void() function pointer */
#define delay_loop ((void(*)()) ((uintptr_t) delay_loop_code | 1))
void wait_ns(unsigned int ns)
{