From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Alex Deucher Subject: [PATCH 3.10 164/173] drm/radeon: use 64-bit math to calculate CTS values for audio (v2) Date: Mon, 2 Dec 2013 11:12:27 -0800 Message-Id: <20131202191201.954672369@linuxfoundation.org> In-Reply-To: <20131202191142.873808297@linuxfoundation.org> References: <20131202191142.873808297@linuxfoundation.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: 3.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Alex Deucher commit 062c2e4363451d49ef840232fe65e8bff0dde2a5 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- drivers/gpu/drm/radeon/r600_hdmi.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) --- 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 */ 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); }