[PATCH] pm2fb: pixclock setting restriction

[PATCH] pm2fb: pixclock setting restriction

[Krzysztof Helt]

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From: Krzysztof Helt <krzysztof.h1@wp.pl>

This patch add restrictions to calculations of m, n and p factors
which sets the pixclock for the Permedia 2V. I found during tests
that synchronization is unstable if m (divisor) is bigger than
half of the n (numerator). The patch dissallows such settings
combination.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>

---



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--- linux-2.6.21.orig/drivers/video/pm2fb.c	2007-04-21 21:34:34.672917412 +0200
+++ linux-2.6.21/drivers/video/pm2fb.c	2007-04-22 19:42:29.715214265 +0200
@@ -302,10 +303,10 @@ static void pm2v_mnp(u32 clk, unsigned c
 	s32 delta = 1000;
 
 	*mm = *nn = *pp = 0;
-	for (n = 1; n; n++) {
-		for ( m = 1; m; m++) {
+	for ( m = 1; m; m++) {
+		for (n = 2 * m + 1; n; n++) {
 			for ( p = 0; p < 2; p++) {
-				f = PM2_REFERENCE_CLOCK * n / (m * (1 << (p + 1)));
+				f = ( PM2_REFERENCE_CLOCK >> ( p + 1 )) * n / m;
 				if ( clk > f - delta && clk < f + delta ) {
 					delta = ( clk > f ) ? clk - f : f - clk;
 					*mm=m;

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[REPOST][PATCH] pm2fb: pixclock setting restriction

[Krzysztof Helt]

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From: Krzysztof Helt <krzysztof.h1@wp.pl>

This patch adds restrictions to calculations of m, n and p factors
which sets the pixclock for the Permedia 2V. I found during tests
that synchronization is unstable if m (divisor) is bigger than
half of the n (numerator). The patch disallows such settings
combination.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
 
---
This patch has fixed range overflow with m > 127 comparing to
previous one.

Regards,
Krzysztof

----------------------------------------------------
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--- linux-2.6.21.orig/drivers/video/pm2fb.c	2007-04-21 21:34:34.672917412 +0200
+++ linux-2.6.21/drivers/video/pm2fb.c	2007-04-22 19:42:29.715214265 +0200
@@ -302,10 +303,10 @@ static void pm2v_mnp(u32 clk, unsigned c
 	s32 delta = 1000;
 
 	*mm = *nn = *pp = 0;
-	for (n = 1; n; n++) {
-		for ( m = 1; m; m++) {
+	for ( m = 1; m < 128; m++) {
+		for (n = 2 * m + 1; n; n++) {
 			for ( p = 0; p < 2; p++) {
-				f = PM2_REFERENCE_CLOCK * n / (m * (1 << (p + 1)));
+				f = ( PM2_REFERENCE_CLOCK >> ( p + 1 )) * n / m;
 				if ( clk > f - delta && clk < f + delta ) {
 					delta = ( clk > f ) ? clk - f : f - clk;
 					*mm=m;

[-- Attachment #3: Type: text/plain, Size: 286 bytes --]

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