samd21: Avoid divides in boot loader

The divide code is huge and overflows flash.

Signed-off-by: Keith Packard <keithp@keithp.com>

diff --git a/src/samd21/ao_flash_samd21.c b/src/samd21/ao_flash_samd21.c
index b0d91c5cdee2e1f482880907cdbf5eea0475661f..502ff35e07710b680972f075f6254709c71975d8 100644 (file)
--- a/src/samd21/ao_flash_samd21.c
+++ b/src/samd21/ao_flash_samd21.c
@@ -38,7 +38,15 @@ samd21_nvmctrl_lock_region(void)
 static uint8_t
 ao_flash_lock_region_bit(void *addr)
 {
-       return (uint8_t) (((uintptr_t) addr) / samd21_nvmctrl_lock_region());
+       uint32_t lock_region = samd21_nvmctrl_lock_region();
+       uintptr_t a = (uintptr_t) addr;
+
+       while (lock_region) {
+               a >>= 1;
+               lock_region >>= 1;
+       }
+
+       return (uint8_t) a;
 }
 
 static uint8_t
@@ -119,10 +127,10 @@ ao_flash_erase_page(uint32_t *page)
 void
 ao_flash_page(uint32_t *page, uint32_t *src)
 {
-       uint32_t        page_size = samd21_nvmctrl_page_size();
-       uint32_t        pages = 256 / page_size;
+       uint32_t        page_shift = samd21_nvmctrl_page_shift();
+       uint32_t        pages = 256 >> page_shift;
        uint32_t        i;
-       uint32_t        per_page = page_size / sizeof(uint32_t);
+       uint32_t        per_page = 1 << (page_shift - 2);
 
        ao_flash_erase_page(page);