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Commit a2098250 authored by Pierre Ossman's avatar Pierre Ossman Committed by Alex Deucher
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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 HDMI spec though.

bug:
https://bugs.freedesktop.org/show_bug.cgi?id=69675



Signed-off-by: default avatarPierre Ossman <pierre@ossman.eu>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent 3e71985f

drivers/gpu/drm/radeon/r600_hdmi.c

+46 −22
Original line number Original line Diff line number Diff line
@@ -24,6 +24,7 @@ 
 * Authors: Christian König

 * Authors: Christian König

 */

 */

#include <linux/hdmi.h>

#include <linux/hdmi.h>

#include <linux/gcd.h>

#include <drm/drmP.h>

#include <drm/drmP.h>

#include <drm/radeon_drm.h>

#include <drm/radeon_drm.h>

#include "radeon.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 */

    {  74250,  4096,  74250,  6272,  82500,  6144,  74250 }, /*  74.25       MHz */

    { 148352,  4096, 148352,  5733, 150670,  6144, 148352 }, /* 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 */

    { 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;

	int n, cts;

	u32 d;

	unsigned long div, mul;





	if (*CTS == 0) {

	/* Safe, but overly large values */

		n = (u64)clock * (u64)N * 1000ULL;

	n = 128 * freq;

		d = 128 * freq;

	cts = clock * 1000;

		do_div(n, d);



		*CTS = n;

	/* Smallest valid fraction */

	}

	div = gcd(n, cts);

	DRM_DEBUG("Using ACR timing N=%d CTS=%d for frequency %d\n",



		  N, *CTS, freq);

	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)

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;

	struct radeon_hdmi_acr res;

	u8 i;

	u8 i;





	for (i = 0; r600_hdmi_predefined_acr[i].clock != clock &&

	/* Precalculated values for common clocks */

	     r600_hdmi_predefined_acr[i].clock != 0; i++)

	for (i = 0; i < ARRAY_SIZE(r600_hdmi_predefined_acr); i++) {

		;

		if (r600_hdmi_predefined_acr[i].clock == clock)

	res = r600_hdmi_predefined_acr[i];

			return r600_hdmi_predefined_acr[i];

	}





	/* In case some CTS are missing */

	/* 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_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_44_1khz, &res.n_44_1khz, 44100);

	r600_hdmi_calc_cts(clock, &res.cts_48khz, res.n_48khz, 48000);

	r600_hdmi_calc_cts(clock, &res.cts_48khz, &res.n_48khz, 48000);





	return res;

	return res;

}

}