Revert "rsa: Optimization of multiplications for Cortex-M0"

This reverts commit 49ff62bf0be5cfc88e092f987d77c18a0b21390a.

BUG=b:200823466
TEST=make buildall -j

Change-Id: I144e310c00d6490d278ca6215bf0a37d3cfc7d4f
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3285751
Reviewed-by: Vadim Sukhomlinov <sukhomlinov@chromium.org>

4 files changed, 6 insertions, 58 deletions

diff --git a/common/rsa.c b/common/rsa.c
index 9350f88554..891614bbfa 100644
--- a/common/rsa.c
+++ b/common/rsa.c
@@ -50,14 +50,14 @@ static void mont_mul_add(const struct rsa_public_key *key,
 			 const uint32_t a,
 			 const uint32_t *b)
 {
-	uint64_t A = mula32(a, b[0], c[0]);
+	uint64_t A = (uint64_t)a * b[0] + c[0];
 	uint32_t d0 = (uint32_t)A * key->n0inv;
-	uint64_t B = mula32(d0, key->n[0], A);
+	uint64_t B = (uint64_t)d0 * key->n[0] + (uint32_t)A;
 	uint32_t i;
 
 	for (i = 1; i < RSANUMWORDS; ++i) {
-		A = (A >> 32) + mula32(a, b[i], c[i]);
-		B = (B >> 32) + mula32(d0, key->n[i], A);
+		A = (A >> 32) + (uint64_t)a * b[i] + c[i];
+		B = (B >> 32) + (uint64_t)d0 * key->n[i] + (uint32_t)A;
 		c[i - 1] = (uint32_t)B;
 	}
 
@@ -78,11 +78,11 @@ static void mont_mul_add_0(const struct rsa_public_key *key,
 			 const uint32_t *b)
 {
 	uint32_t d0 = c[0] * key->n0inv;
-	uint64_t B = mula32(d0, key->n[0], c[0]);
+	uint64_t B = (uint64_t)d0 * key->n[0] + c[0];
 	uint32_t i;
 
 	for (i = 1; i < RSANUMWORDS; ++i) {
-		B = (B >> 32) + mula32(d0, key->n[i], c[i]);
+		B = (B >> 32) + (uint64_t)d0 * key->n[i] + c[i];
 		c[i - 1] = (uint32_t)B;
 	}
 
diff --git a/include/config.h b/include/config.h
index 523bf2045b..aef1d301c5 100644
--- a/include/config.h
+++ b/include/config.h
@@ -276,13 +276,6 @@
 /* Support AP Warm reset Interrupt. */
 #undef CONFIG_AP_WARM_RESET_INTERRUPT
 
-/*
- * Defined if core/ code provides assembly optimized implementation of
- * multiply-accumulate operations (32-bit operands, 64-bit result), for the
- * cores that lack native instructions.
- */
-#undef CONFIG_ASSEMBLY_MULA32
-
 /* Support audio codec. */
 #undef CONFIG_AUDIO_CODEC
 /* Audio codec caps. */
diff --git a/include/util.h b/include/util.h
index d05869305d..90e52dd2a5 100644
--- a/include/util.h
+++ b/include/util.h
@@ -222,24 +222,6 @@ int parse_offset_size(int argc, char **argv, int shift,
  */
 void hexdump(const uint8_t *data, int len);
 
-#ifdef CONFIG_ASSEMBLY_MULA32
-/*
- * Compute (a*b)+c, where a, b, c are 32-bit integers, and the result is
- * 64-bit long.
- */
-uint64_t mula32(uint32_t a, uint32_t b, uint32_t c);
-#else
-static inline uint64_t mula32(uint32_t a, uint32_t b, uint32_t c)
-{
-	uint64_t ret = a;
-
-	ret *= b;
-	ret += c;
-
-	return ret;
-}
-#endif
-
 #ifdef __cplusplus
 }
 #endif
diff --git a/test/utils.c b/test/utils.c
index 119ce98543..1cd86830ed 100644
--- a/test/utils.c
+++ b/test/utils.c
@@ -12,7 +12,6 @@
 #include "test_util.h"
 #include "timer.h"
 #include "util.h"
-#include "watchdog.h"
 
 static int test_memmove(void)
 {
@@ -357,31 +356,6 @@ static int test_cond_t(void)
 	return EC_SUCCESS;
 }
 
-static int test_mula32(void)
-{
-	uint64_t r = 0x0;
-	uint32_t b = 0x1;
-	uint32_t c = 0x1;
-	uint32_t i;
-	timestamp_t t0, t1;
-
-	t0 = get_time();
-	for (i = 0; i < 5000000; i++) {
-		r = mula32(b, c, r + (r >> 32));
-		b = (b << 13) ^ (b >> 2) ^ i;
-		c = (c << 16) ^ (c >> 7) ^ i;
-		watchdog_reload();
-	}
-	t1 = get_time();
-
-	ccprintf("After %d iterations, r=%08x%08x (time: %d)\n", i,
-		(uint32_t)(r >> 32), (uint32_t)r, t1.le.lo-t0.le.lo);
-	TEST_ASSERT(r == 0x9df59b9fb0ab9d96L);
-
-	/* well okay then */
-	return EC_SUCCESS;
-}
-
 static int test_bytes_are_trivial(void)
 {
 	static const uint8_t all0x00[] = { 0x00, 0x00, 0x00 };
@@ -416,7 +390,6 @@ void run_test(void)
 	RUN_TEST(test_shared_mem);
 	RUN_TEST(test_scratchpad);
 	RUN_TEST(test_cond_t);
-	RUN_TEST(test_mula32);
 	RUN_TEST(test_bytes_are_trivial);
 
 	test_print_result();