Attachment 88776 Details for Bug 69675 – patch 2/2: improve ACR calculation

[patch] patch 2/2: improve ACR calculation

0002-drm-radeon-audio-improve-ACR-calculation.patch (text/plain), 3.68 KB, created by Pierre Ossman on 2013-11-06 19:13:26 UTC

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Creator: Pierre Ossman

Created: 2013-11-06 19:13:26 UTC

Size: 3.68 KB

patch

obsolete

>From 5b14c9987e509c6b75b431442b83a400aa1380c0 Mon Sep 17 00:00:00 2001
>From: Pierre Ossman <pierre@ossman.eu>
>Date: Wed, 6 Nov 2013 20:09:08 +0100
>Subject: [PATCH 2/2] drm/radeon/audio: improve ACR calculation
>
>In order to have any realistic chance of calculating proper
>ACR values, we need to be able to calculate both N and CTS,
>not just CTS. We still aim for the ideal N as specified in
>the CEC HDMI spec though.
>
>Signed-off-by: Pierre Ossman <pierre@ossman.eu>
>---
> drivers/gpu/drm/radeon/r600_hdmi.c | 68 ++++++++++++++++++++++++++------------
> 1 file changed, 46 insertions(+), 22 deletions(-)
>
>diff --git a/drivers/gpu/drm/radeon/r600_hdmi.c b/drivers/gpu/drm/radeon/r600_hdmi.c
>index c8dd566..615c5b2 100644
>--- a/drivers/gpu/drm/radeon/r600_hdmi.c
>+++ b/drivers/gpu/drm/radeon/r600_hdmi.c
>@@ -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"
>@@ -67,25 +68,47 @@ static const struct radeon_hdmi_acr r600_hdmi_predefined_acr[] = {
>     {  74250,  4096,  74250,  6272,  82500,  6144,  74250 }, /*  74.25       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;
>-
>-	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);
>+	int n, cts;
>+	unsigned long div, mul;
>+
>+	/* 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 +116,16 @@ struct radeon_hdmi_acr r600_hdmi_acr(uint32_t clock)
> 	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];
>+	/* 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];
>+	}
> 
>-	/* 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);
>+	/* 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;
> }
>-- 
>1.8.3.1
>

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

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