drivers/gpu/drm/amd/amdgpu/amdgpu_afmt.c

   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 }