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Commit da746d4e authored by Ben Skeggs's avatar Ben Skeggs
Browse files

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: default avatarBen Skeggs <bskeggs@redhat.com>
parent dceef5d8

drivers/gpu/drm/nouveau/core/subdev/clock/pllnva3.c

+11 −3
Original line number Diff line number Diff line
@@ -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)



		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;

		}

	}