1 /*
2  * Copyright 2008 Advanced Micro Devices, Inc.
3  * Copyright 2008 Red Hat Inc.
4  * Copyright 2009 Christian König.
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a
7  * copy of this software and associated documentation files (the "Software"),
8  * to deal in the Software without restriction, including without limitation
9  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
10  * and/or sell copies of the Software, and to permit persons to whom the
11  * Software is furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the Software.
15  *
16  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19  * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
20  * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
21  * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
22  * OTHER DEALINGS IN THE SOFTWARE.
23  *
24  * Authors: Christian König
25  */
26 #include <linux/hdmi.h>
27 #include <linux/gcd.h>
28 #include <drm/drmP.h>
29 #include <drm/amdgpu_drm.h>
30 #include "amdgpu.h"
31 
32 static const struct amdgpu_afmt_acr amdgpu_afmt_predefined_acr[] = {
33     /*	     32kHz	  44.1kHz	48kHz    */
34     /* Clock      N     CTS      N     CTS      N     CTS */
35     {  25175,  4096,  25175, 28224, 125875,  6144,  25175 }, /*  25,20/1.001 MHz */
36     {  25200,  4096,  25200,  6272,  28000,  6144,  25200 }, /*  25.20       MHz */
37     {  27000,  4096,  27000,  6272,  30000,  6144,  27000 }, /*  27.00       MHz */
38     {  27027,  4096,  27027,  6272,  30030,  6144,  27027 }, /*  27.00*1.001 MHz */
39     {  54000,  4096,  54000,  6272,  60000,  6144,  54000 }, /*  54.00       MHz */
40     {  54054,  4096,  54054,  6272,  60060,  6144,  54054 }, /*  54.00*1.001 MHz */
41     {  74176,  4096,  74176,  5733,  75335,  6144,  74176 }, /*  74.25/1.001 MHz */
42     {  74250,  4096,  74250,  6272,  82500,  6144,  74250 }, /*  74.25       MHz */
43     { 148352,  4096, 148352,  5733, 150670,  6144, 148352 }, /* 148.50/1.001 MHz */
44     { 148500,  4096, 148500,  6272, 165000,  6144, 148500 }, /* 148.50       MHz */
45 };
46 
47 
48 /*
49  * calculate CTS and N values if they are not found in the table
50  */
51 static void amdgpu_afmt_calc_cts(uint32_t clock, int *CTS, int *N, int freq)
52 {
53 	int n, cts;
54 	unsigned long div, mul;
55 
56 	/* Safe, but overly large values */
57 	n = 128 * freq;
58 	cts = clock * 1000;
59 
60 	/* Smallest valid fraction */
61 	div = gcd(n, cts);
62 
63 	n /= div;
64 	cts /= div;
65 
66 	/*
67 	 * The optimal N is 128*freq/1000. Calculate the closest larger
68 	 * value that doesn't truncate any bits.
69 	 */
70 	mul = ((128*freq/1000) + (n-1))/n;
71 
72 	n *= mul;
73 	cts *= mul;
74 
75 	/* Check that we are in spec (not always possible) */
76 	if (n < (128*freq/1500))
77 		pr_warn("Calculated ACR N value is too small. You may experience audio problems.\n");
78 	if (n > (128*freq/300))
79 		pr_warn("Calculated ACR N value is too large. You may experience audio problems.\n");
80 
81 	*N = n;
82 	*CTS = cts;
83 
84 	DRM_DEBUG("Calculated ACR timing N=%d CTS=%d for frequency %d\n",
85 		  *N, *CTS, freq);
86 }
87 
88 struct amdgpu_afmt_acr amdgpu_afmt_acr(uint32_t clock)
89 {
90 	struct amdgpu_afmt_acr res;
91 	u8 i;
92 
93 	/* Precalculated values for common clocks */
94 	for (i = 0; i < ARRAY_SIZE(amdgpu_afmt_predefined_acr); i++) {
95 		if (amdgpu_afmt_predefined_acr[i].clock == clock)
96 			return amdgpu_afmt_predefined_acr[i];
97 	}
98 
99 	/* And odd clocks get manually calculated */
100 	amdgpu_afmt_calc_cts(clock, &res.cts_32khz, &res.n_32khz, 32000);
101 	amdgpu_afmt_calc_cts(clock, &res.cts_44_1khz, &res.n_44_1khz, 44100);
102 	amdgpu_afmt_calc_cts(clock, &res.cts_48khz, &res.n_48khz, 48000);
103 
104 	return res;
105 }
106