Attachment 88476 Details for Bug 69675 – properly calculate both N and CTS

[patch] properly calculate both N and CTS

file_69675.txt (text/plain), 4.03 KB, created by Pierre Ossman on 2013-11-01 14:17:53 UTC

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Creator: Pierre Ossman

Created: 2013-11-01 14:17:53 UTC

Size: 4.03 KB

patch

obsolete

>--- drivers/gpu/drm/radeon/r600_hdmi.c.orig	2013-11-01 15:13:55.000000000 +0100
>+++ drivers/gpu/drm/radeon/r600_hdmi.c	2013-11-01 15:13:22.003724698 +0100
>@@ -24,6 +24,7 @@
>  * Authors: Christian KÃ¶nig
>  */
> #include <linux/hdmi.h>
>+#include <linux/gcd.h>
> #include <drm/drmP.h>
> #include <drm/radeon_drm.h>
> #include "radeon.h"
>@@ -57,35 +58,56 @@
> static const struct radeon_hdmi_acr r600_hdmi_predefined_acr[] = {
>     /*	     32kHz	  44.1kHz	48kHz    */
>     /* Clock      N     CTS      N     CTS      N     CTS */
>-    {  25175,  4576,  28125,  7007,  31250,  6864,  28125 }, /*  25,20/1.001 MHz */
>+    {  25175,  4096,  25175, 28224, 125875,  6144,  25175 }, /*  25,20/1.001 MHz */
>     {  25200,  4096,  25200,  6272,  28000,  6144,  25200 }, /*  25.20       MHz */
>     {  27000,  4096,  27000,  6272,  30000,  6144,  27000 }, /*  27.00       MHz */
>     {  27027,  4096,  27027,  6272,  30030,  6144,  27027 }, /*  27.00*1.001 MHz */
>     {  54000,  4096,  54000,  6272,  60000,  6144,  54000 }, /*  54.00       MHz */
>     {  54054,  4096,  54054,  6272,  60060,  6144,  54054 }, /*  54.00*1.001 MHz */
>-    {  74176, 11648, 210937, 17836, 234375, 11648, 140625 }, /*  74.25/1.001 MHz */
>+    {  74176,  4096,  74176,  5733,  75335,  6144,  74176 }, /*  74.25/1.001 MHz */
>     {  74250,  4096,  74250,  6272,  82500,  6144,  74250 }, /*  74.25       MHz */
>-    { 148352, 11648, 421875,  8918, 234375,  5824, 140625 }, /* 148.50/1.001 MHz */
>+    { 148352,  4096, 148352,  5733, 150670,  6144, 148352 }, /* 148.50/1.001 MHz */
>     { 148500,  4096, 148500,  6272, 165000,  6144, 148500 }, /* 148.50       MHz */
>-    {      0,  4096,      0,  6272,      0,  6144,      0 }  /* Other */
> };
> 
> /*
>- * calculate CTS value if it's not found in the table
>+ * calculate CTS and N values if they are not found in the table
>  */
>-static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int N, int freq)
>+static void r600_hdmi_calc_cts(uint32_t clock, int *CTS, int *N, int freq)
> {
>-	u64 n;
>-	u32 d;
>+	int n, cts;
>+	unsigned long div, mul;
> 
>-	if (*CTS == 0) {
>-		n = (u64)clock * (u64)N * 1000ULL;
>-		d = 128 * freq;
>-		do_div(n, d);
>-		*CTS = n;
>-	}
>-	DRM_DEBUG("Using ACR timing N=%d CTS=%d for frequency %d\n",
>-		  N, *CTS, freq);
>+	/* Safe, but overly large values */
>+	n = 128 * freq;
>+	cts = clock * 1000;
>+
>+	/* Smallest valid fraction */
>+	div = gcd(n, cts);
>+
>+	n /= div;
>+	cts /= div;
>+
>+	/*
>+	 * The optimal N is 128*freq/1000. Calculate the closest larger
>+	 * value that doesn't truncate any bits.
>+	 */
>+	mul = ((128*freq/1000) + (n-1))/n;
>+
>+	n *= mul;
>+	cts *= mul;
>+
>+	/* Check that we are in spec (not always possible) */
>+	if (n < (128*freq/1500))
>+		printk(KERN_WARNING "Calculated ACR N value is too small. You may experience audio problems.\n");
>+	if (n > (128*freq/300))
>+		printk(KERN_WARNING "Calculated ACR N value is too large. You may experience audio problems.\n");
>+
>+	*N = n;
>+	*CTS = cts;
>+
>+	DRM_DEBUG("Calculated ACR timing N=%d CTS=%d for frequency %d\n",
>+		  *N, *CTS, freq);
> }
> 
> struct radeon_hdmi_acr r600_hdmi_acr(uint32_t clock)
>@@ -93,15 +115,17 @@
> 	struct radeon_hdmi_acr res;
> 	u8 i;
> 
>-	for (i = 0; r600_hdmi_predefined_acr[i].clock != clock &&
>-	     r600_hdmi_predefined_acr[i].clock != 0; i++)
>-		;
>-	res = r600_hdmi_predefined_acr[i];
>-
>-	/* In case some CTS are missing */
>-	r600_hdmi_calc_cts(clock, &res.cts_32khz, res.n_32khz, 32000);
>-	r600_hdmi_calc_cts(clock, &res.cts_44_1khz, res.n_44_1khz, 44100);
>-	r600_hdmi_calc_cts(clock, &res.cts_48khz, res.n_48khz, 48000);
>+	/* Precalculated values for common clocks */
>+	for (i = 0; i < ARRAY_SIZE(r600_hdmi_predefined_acr); i++) {
>+		if (r600_hdmi_predefined_acr[i].clock == clock) {
>+			return r600_hdmi_predefined_acr[i];
>+		}
>+	}
>+
>+	/* And odd clocks get manually calculated */
>+	r600_hdmi_calc_cts(clock, &res.cts_32khz, &res.n_32khz, 32000);
>+	r600_hdmi_calc_cts(clock, &res.cts_44_1khz, &res.n_44_1khz, 44100);
>+	r600_hdmi_calc_cts(clock, &res.cts_48khz, &res.n_48khz, 48000);
> 
> 	return res;
> }

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Attachments on bug 69675: 86598 | 86739 | 86740 | 86741 | 86856 | 88450 | 88476 | 88775 | 88776

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