From da746d4ec9605302386bab46ea8dfdd66f94560c Mon Sep 17 00:00:00 2001 From: Ben Skeggs Date: Thu, 24 Jan 2013 12:15:45 +1000 Subject: [PATCH] drm/nva3/clk: minor improvements to fractional N calculation Helps us to get identical numbers to the binary driver for (at least) Kepler memory PLLs, and fixes a rounding error. Signed-off-by: Ben Skeggs --- .../gpu/drm/nouveau/core/subdev/clock/pllnva3.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c b/drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c index 4497378ba1e8..2fe1f712eefa 100644 --- a/drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c +++ b/drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c @@ -50,8 +50,15 @@ nva3_pll_calc(struct nouveau_subdev *subdev, struct nvbios_pll *info, u32 tmp = freq * *P * M; N = tmp / info->refclk; fN = tmp % info->refclk; - if (!pfN && fN >= info->refclk / 2) - N++; + + if (!pfN) { + if (fN >= info->refclk / 2) + N++; + } else { + if (fN < info->refclk / 2) + N--; + fN = tmp - (N * info->refclk); + } if (N < info->vco1.min_n) continue; @@ -66,7 +73,8 @@ nva3_pll_calc(struct nouveau_subdev *subdev, struct nvbios_pll *info, } if (pfN) { - *pfN = (((fN << 13) / info->refclk) - 4096) & 0xffff; + *pfN = ((fN << 13) + info->refclk / 2) / info->refclk; + *pfN = (*pfN - 4096) & 0xffff; return freq; } } -- 2.20.1