From 7fc80b7bd682b47825e806018cca8ff7dc6bb55a Mon Sep 17 00:00:00 2001 From: Krzysztof Helt Date: Wed, 23 Jul 2008 21:31:44 -0700 Subject: [PATCH] neofb: simplify clock calculation There is nothing to gain by converting value in kHz to fixed point MHz. Just calculate everything in kHz. A reorder of the loop allows reducing number of iterations (check if frequency is not too high already). Signed-off-by: Krzysztof Helt Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/video/neofb.c | 32 ++++++++++++++------------------ 1 file changed, 14 insertions(+), 18 deletions(-) diff --git a/drivers/video/neofb.c b/drivers/video/neofb.c index 5246b0402d76..b033e5a4dc86 100644 --- a/drivers/video/neofb.c +++ b/drivers/video/neofb.c @@ -201,7 +201,6 @@ static int neoFindMode(int xres, int yres, int depth) * * Determine the closest clock frequency to the one requested. */ -#define REF_FREQ 0xe517 /* 14.31818 in 20.12 fixed point */ #define MAX_N 127 #define MAX_D 31 #define MAX_F 1 @@ -211,27 +210,24 @@ static void neoCalcVCLK(const struct fb_info *info, { int n, d, f; int n_best = 0, d_best = 0, f_best = 0; - long f_best_diff = (0x7ffff << 12); /* 20.12 */ - long f_target = (freq << 12) / 1000; /* 20.12 */ + long f_best_diff = 0x7ffff; for (f = 0; f <= MAX_F; f++) - for (n = 0; n <= MAX_N; n++) - for (d = 0; d <= MAX_D; d++) { - long f_out; /* 20.12 */ - long f_diff; /* 20.12 */ - - f_out = - ((((n + 1) << 12) / ((d + - 1) * - (1 << f))) >> 12) - * REF_FREQ; - f_diff = abs(f_out - f_target); - if (f_diff < f_best_diff) { + for (d = 0; d <= MAX_D; d++) + for (n = 0; n <= MAX_N; n++) { + long f_out; + long f_diff; + + f_out = ((14318 * (n + 1)) / (d + 1)) >> f; + f_diff = abs(f_out - freq); + if (f_diff <= f_best_diff) { f_best_diff = f_diff; n_best = n; d_best = d; f_best = f; } + if (f_out > freq) + break; } if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 || @@ -248,11 +244,11 @@ static void neoCalcVCLK(const struct fb_info *info, par->VCLK3Denominator = d_best; #ifdef NEOFB_DEBUG - printk("neoVCLK: f:%d NumLow=%d NumHi=%d Den=%d Df=%d\n", - f_target >> 12, + printk(KERN_DEBUG "neoVCLK: f:%ld NumLow=%d NumHi=%d Den=%d Df=%ld\n", + freq, par->VCLK3NumeratorLow, par->VCLK3NumeratorHigh, - par->VCLK3Denominator, f_best_diff >> 12); + par->VCLK3Denominator, f_best_diff); #endif } -- 2.20.1