From 89ecc32b90565ace078c4a84d4406a4d1f86821a Mon Sep 17 00:00:00 2001 From: Keith Packard Date: Sat, 17 Dec 2016 20:58:36 -0800 Subject: altos/arm: Align data so that gcc 5.4 doesn't do byte-accesses. Add -Wcast-align Gcc 5.4.1 tracks alignment of data through assignments, so that a uint32_t pointer which comes from byte-aligned uint8_t data: extern uint8_t foo[]; uint32_t *q = (void *) foo; Fetches and stores through this pointer are done bytewise. This is slow (meh), but if q references a device register, things to bad very quickly. This patch works around this bug in the compiler by adding __attribute__((aligned(4))) tags to some variables, or changing them from uint8_t to uint32_t. Places doing this will now be caught as I've added -Wcast-align to the compiler flags. That required adding (void *) casts, after the relevant code was checked to make sure the compiler could tell that the addresses were aligned. Signed-off-by: Keith Packard --- src/drivers/ao_trng_send.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'src/drivers/ao_trng_send.c') diff --git a/src/drivers/ao_trng_send.c b/src/drivers/ao_trng_send.c index 85034efd..b1227aaa 100644 --- a/src/drivers/ao_trng_send.c +++ b/src/drivers/ao_trng_send.c @@ -104,7 +104,7 @@ ao_trng_get_cooked(uint16_t *buf) { uint16_t i; uint16_t t; - uint32_t *rnd = (uint32_t *) ao_adc_ring; + uint32_t *rnd = (uint32_t *) (void *) ao_adc_ring; uint8_t mismatch = 0; t = ao_adc_get(AO_USB_IN_SIZE) >> 1; /* one 16-bit value per output byte */ -- cgit v1.2.3