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authorKrzysztof Helt <krzysztof.h1@wp.pl>2008-07-24 00:31:44 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-24 13:47:41 -0400
commit7fc80b7bd682b47825e806018cca8ff7dc6bb55a (patch)
treed408bf73887f4788e0d5e70c91320fff1391f624 /drivers
parent5798712d608f5ebad994487748a2ccf3cc613d78 (diff)
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 <krzysztof.h1@wp.pl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/video/neofb.c32
1 files 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)
201 * 201 *
202 * Determine the closest clock frequency to the one requested. 202 * Determine the closest clock frequency to the one requested.
203 */ 203 */
204#define REF_FREQ 0xe517 /* 14.31818 in 20.12 fixed point */
205#define MAX_N 127 204#define MAX_N 127
206#define MAX_D 31 205#define MAX_D 31
207#define MAX_F 1 206#define MAX_F 1
@@ -211,27 +210,24 @@ static void neoCalcVCLK(const struct fb_info *info,
211{ 210{
212 int n, d, f; 211 int n, d, f;
213 int n_best = 0, d_best = 0, f_best = 0; 212 int n_best = 0, d_best = 0, f_best = 0;
214 long f_best_diff = (0x7ffff << 12); /* 20.12 */ 213 long f_best_diff = 0x7ffff;
215 long f_target = (freq << 12) / 1000; /* 20.12 */
216 214
217 for (f = 0; f <= MAX_F; f++) 215 for (f = 0; f <= MAX_F; f++)
218 for (n = 0; n <= MAX_N; n++) 216 for (d = 0; d <= MAX_D; d++)
219 for (d = 0; d <= MAX_D; d++) { 217 for (n = 0; n <= MAX_N; n++) {
220 long f_out; /* 20.12 */ 218 long f_out;
221 long f_diff; /* 20.12 */ 219 long f_diff;
222 220
223 f_out = 221 f_out = ((14318 * (n + 1)) / (d + 1)) >> f;
224 ((((n + 1) << 12) / ((d + 222 f_diff = abs(f_out - freq);
225 1) * 223 if (f_diff <= f_best_diff) {
226 (1 << f))) >> 12)
227 * REF_FREQ;
228 f_diff = abs(f_out - f_target);
229 if (f_diff < f_best_diff) {
230 f_best_diff = f_diff; 224 f_best_diff = f_diff;
231 n_best = n; 225 n_best = n;
232 d_best = d; 226 d_best = d;
233 f_best = f; 227 f_best = f;
234 } 228 }
229 if (f_out > freq)
230 break;
235 } 231 }
236 232
237 if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 || 233 if (info->fix.accel == FB_ACCEL_NEOMAGIC_NM2200 ||
@@ -248,11 +244,11 @@ static void neoCalcVCLK(const struct fb_info *info,
248 par->VCLK3Denominator = d_best; 244 par->VCLK3Denominator = d_best;
249 245
250#ifdef NEOFB_DEBUG 246#ifdef NEOFB_DEBUG
251 printk("neoVCLK: f:%d NumLow=%d NumHi=%d Den=%d Df=%d\n", 247 printk(KERN_DEBUG "neoVCLK: f:%ld NumLow=%d NumHi=%d Den=%d Df=%ld\n",
252 f_target >> 12, 248 freq,
253 par->VCLK3NumeratorLow, 249 par->VCLK3NumeratorLow,
254 par->VCLK3NumeratorHigh, 250 par->VCLK3NumeratorHigh,
255 par->VCLK3Denominator, f_best_diff >> 12); 251 par->VCLK3Denominator, f_best_diff);
256#endif 252#endif
257} 253}
258 254