1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Copyright (C) 2013 NVIDIA Corporation
4 */
5
6#include <linux/errno.h>
7#include <linux/kernel.h>
8
9#include "mipi-phy.h"
10
11/*
12 * Default D-PHY timings based on MIPI D-PHY specification. Derived from the
13 * valid ranges specified in Section 6.9, Table 14, Page 40 of the D-PHY
14 * specification (v1.2) with minor adjustments.
15 */
16int mipi_dphy_timing_get_default(struct mipi_dphy_timing *timing,
17				 unsigned long period)
18{
19	timing->clkmiss = 0;
20	timing->clkpost = 70 + 52 * period;
21	timing->clkpre = 8;
22	timing->clkprepare = 65;
23	timing->clksettle = 95;
24	timing->clktermen = 0;
25	timing->clktrail = 80;
26	timing->clkzero = 260;
27	timing->dtermen = 0;
28	timing->eot = 0;
29	timing->hsexit = 120;
30	timing->hsprepare = 65 + 5 * period;
31	timing->hszero = 145 + 5 * period;
32	timing->hssettle = 85 + 6 * period;
33	timing->hsskip = 40;
34
35	/*
36	 * The MIPI D-PHY specification (Section 6.9, v1.2, Table 14, Page 40)
37	 * contains this formula as:
38	 *
39	 *     T_HS-TRAIL = max(n * 8 * period, 60 + n * 4 * period)
40	 *
41	 * where n = 1 for forward-direction HS mode and n = 4 for reverse-
42	 * direction HS mode. There's only one setting and this function does
43	 * not parameterize on anything other that period, so this code will
44	 * assumes that reverse-direction HS mode is supported and uses n = 4.
45	 */
46	timing->hstrail = max(4 * 8 * period, 60 + 4 * 4 * period);
47
48	timing->init = 100000;
49	timing->lpx = 60;
50	timing->taget = 5 * timing->lpx;
51	timing->tago = 4 * timing->lpx;
52	timing->tasure = 2 * timing->lpx;
53	timing->wakeup = 1000000;
54
55	return 0;
56}
57
58/*
59 * Validate D-PHY timing according to MIPI D-PHY specification (v1.2, Section
60 * Section 6.9 "Global Operation Timing Parameters").
61 */
62int mipi_dphy_timing_validate(struct mipi_dphy_timing *timing,
63			      unsigned long period)
64{
65	if (timing->clkmiss > 60)
66		return -EINVAL;
67
68	if (timing->clkpost < (60 + 52 * period))
69		return -EINVAL;
70
71	if (timing->clkpre < 8)
72		return -EINVAL;
73
74	if (timing->clkprepare < 38 || timing->clkprepare > 95)
75		return -EINVAL;
76
77	if (timing->clksettle < 95 || timing->clksettle > 300)
78		return -EINVAL;
79
80	if (timing->clktermen > 38)
81		return -EINVAL;
82
83	if (timing->clktrail < 60)
84		return -EINVAL;
85
86	if (timing->clkprepare + timing->clkzero < 300)
87		return -EINVAL;
88
89	if (timing->dtermen > 35 + 4 * period)
90		return -EINVAL;
91
92	if (timing->eot > 105 + 12 * period)
93		return -EINVAL;
94
95	if (timing->hsexit < 100)
96		return -EINVAL;
97
98	if (timing->hsprepare < 40 + 4 * period ||
99	    timing->hsprepare > 85 + 6 * period)
100		return -EINVAL;
101
102	if (timing->hsprepare + timing->hszero < 145 + 10 * period)
103		return -EINVAL;
104
105	if ((timing->hssettle < 85 + 6 * period) ||
106	    (timing->hssettle > 145 + 10 * period))
107		return -EINVAL;
108
109	if (timing->hsskip < 40 || timing->hsskip > 55 + 4 * period)
110		return -EINVAL;
111
112	if (timing->hstrail < max(8 * period, 60 + 4 * period))
113		return -EINVAL;
114
115	if (timing->init < 100000)
116		return -EINVAL;
117
118	if (timing->lpx < 50)
119		return -EINVAL;
120
121	if (timing->taget != 5 * timing->lpx)
122		return -EINVAL;
123
124	if (timing->tago != 4 * timing->lpx)
125		return -EINVAL;
126
127	if (timing->tasure < timing->lpx || timing->tasure > 2 * timing->lpx)
128		return -EINVAL;
129
130	if (timing->wakeup < 1000000)
131		return -EINVAL;
132
133	return 0;
134}
135