kernel/drivers/gpu/drm/tegra/mipi-phy.c

   1 /*
   2  * Copyright (C) 2013 NVIDIA Corporation
   3  *
   4  * This program is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU General Public License version 2 as
   6  * published by the Free Software Foundation.
   7  */
   8
   9 #include <linux/errno.h>
  10 #include <linux/kernel.h>
  11
  12 #include "mipi-phy.h"
  13
  14 /*
  15  * Default D-PHY timings based on MIPI D-PHY specification. Derived from the
  16  * valid ranges specified in Section 6.9, Table 14, Page 40 of the D-PHY
  17  * specification (v1.2) with minor adjustments.
  18  */
  19 int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
  20                                  unsigned long period)
  21 {
  22         timing->clkmiss = 0;
  23         timing->clkpost = 70 + 52 * period;
  24         timing->clkpre = 8;
  25         timing->clkprepare = 65;
  26         timing->clksettle = 95;
  27         timing->clktermen = 0;
  28         timing->clktrail = 80;
  29         timing->clkzero = 260;
  30         timing->dtermen = 0;
  31         timing->eot = 0;
  32         timing->hsexit = 120;
  33         timing->hsprepare = 65 + 5 * period;
  34         timing->hszero = 145 + 5 * period;
  35         timing->hssettle = 85 + 6 * period;
  36         timing->hsskip = 40;
  37
  38         /*
  39          * The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
  40          * contains this formula as:
  41          *
  42          *     T_HS-TRAIL = max(n * 8 * period, 60 + n * 4 * period)
  43          *
  44          * where n = 1 for forward-direction HS mode and n = 4 for reverse-
  45          * direction HS mode. There's only one setting and this function does
  46          * not parameterize on anything other that period, so this code will
  47          * assumes that reverse-direction HS mode is supported and uses n = 4.
  48          */
  49         timing->hstrail = max(4 * 8 * period, 60 + 4 * 4 * period);
  50
  51         timing->init = 100000;
  52         timing->lpx = 60;
  53         timing->taget = 5 * timing->lpx;
  54         timing->tago = 4 * timing->lpx;
  55         timing->tasure = 2 * timing->lpx;
  56         timing->wakeup = 1000000;
  57
  58         return 0;
  59 }
  60
  61 /*
  62  * Validate D-PHY timing according to MIPI D-PHY specification (v1.2, Section
  63  * Section 6.9 "Global Operation Timing Parameters").
  64  */
  65 int mipi_dphy_timing_validate(struct mipi_dphy_timing *timing,
  66                               unsigned long period)
  67 {
  68         if (timing->clkmiss > 60)
  69                 return -EINVAL;
  70
  71         if (timing->clkpost < (60 + 52 * period))
  72                 return -EINVAL;
  73
  74         if (timing->clkpre < 8)
  75                 return -EINVAL;
  76
  77         if (timing->clkprepare < 38 || timing->clkprepare > 95)
  78                 return -EINVAL;
  79
  80         if (timing->clksettle < 95 || timing->clksettle > 300)
  81                 return -EINVAL;
  82
  83         if (timing->clktermen > 38)
  84                 return -EINVAL;
  85
  86         if (timing->clktrail < 60)
  87                 return -EINVAL;
  88
  89         if (timing->clkprepare + timing->clkzero < 300)
  90                 return -EINVAL;
  91
  92         if (timing->dtermen > 35 + 4 * period)
  93                 return -EINVAL;
  94
  95         if (timing->eot > 105 + 12 * period)
  96                 return -EINVAL;
  97
  98         if (timing->hsexit < 100)
  99                 return -EINVAL;
 100
 101         if (timing->hsprepare < 40 + 4 * period ||
 102             timing->hsprepare > 85 + 6 * period)
 103                 return -EINVAL;
 104
 105         if (timing->hsprepare + timing->hszero < 145 + 10 * period)
 106                 return -EINVAL;
 107
 108         if ((timing->hssettle < 85 + 6 * period) ||
 109             (timing->hssettle > 145 + 10 * period))
 110                 return -EINVAL;
 111
 112         if (timing->hsskip < 40 || timing->hsskip > 55 + 4 * period)
 113                 return -EINVAL;
 114
 115         if (timing->hstrail < max(8 * period, 60 + 4 * period))
 116                 return -EINVAL;
 117
 118         if (timing->init < 100000)
 119                 return -EINVAL;
 120
 121         if (timing->lpx < 50)
 122                 return -EINVAL;
 123
 124         if (timing->taget != 5 * timing->lpx)
 125                 return -EINVAL;
 126
 127         if (timing->tago != 4 * timing->lpx)
 128                 return -EINVAL;
 129
 130         if (timing->tasure < timing->lpx || timing->tasure > 2 * timing->lpx)
 131                 return -EINVAL;
 132
 133         if (timing->wakeup < 1000000)
 134                 return -EINVAL;
 135
 136         return 0;
 137 }