From: Keith Packard <keithp@keithp.com>
Date: Sun, 6 Nov 2022 23:09:55 +0000 (-0800)
Subject: samd21: Avoid divides in boot loader
X-Git-Tag: 1.9.13~1^2~26^2~47
X-Git-Url: https://git.gag.com/?p=fw%2Faltos;a=commitdiff_plain;h=cbff1483ae7469d3961341a1cfdfeb8b4bb557c1

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 b0d91c5c..502ff35e 100644
--- 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);