From 6a4a51f43cc6635c7b731d9fb2e1e32333d594fe Mon Sep 17 00:00:00 2001 From: Alex Deucher Date: Fri, 27 Sep 2013 18:09:54 -0400 Subject: [PATCH 1/3] drm/radeon: use 64-bit math to calculate CTS values for audio (v2) Avoid losing precision. See bug: https://bugs.freedesktop.org/show_bug.cgi?id=69675 v2: fix math as per Anssi's comments. Signed-off-by: Alex Deucher --- drivers/gpu/drm/radeon/r600_hdmi.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c index b0fa600..49043a5 100644 --- a/drivers/gpu/drm/radeon/r600_hdmi.c +++ b/drivers/gpu/drm/radeon/r600_hdmi.c @@ -75,8 +75,15 @@ static const struct radeon_hdmi_acr r600_hdmi_predefined_acr[] = { */ static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int N, int freq) { - if (*CTS == 0) - *CTS = clock * N / (128 * freq) * 1000; + u64 n; + u32 d; + + if (*CTS == 0) { + n = (u64)clock * (u64)N * 1000ULL; + d = 128 * freq; + do_div(n, d); + *CTS = n; + } DRM_DEBUG("Using ACR timing N=%d CTS=%d for frequency %d\n", N, *CTS, freq); } -- 1.8.3.1