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 */
19int 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 */
65int 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}
138