1/*
  2 * Copyright 2012 Red Hat Inc.
  3 *
  4 * Permission is hereby granted, free of charge, to any person obtaining a
  5 * copy of this software and associated documentation files (the "Software"),
  6 * to deal in the Software without restriction, including without limitation
  7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  8 * and/or sell copies of the Software, and to permit persons to whom the
  9 * Software is furnished to do so, subject to the following conditions:
 10 *
 11 * The above copyright notice and this permission notice shall be included in
 12 * all copies or substantial busions of the Software.
 13 *
 14 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 15 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 16 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
 17 * THE COPYRIGHT HOLDER(S) OR AUTHOR(S) BE LIABLE FOR ANY CLAIM, DAMAGES OR
 18 * OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
 19 * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 20 * OTHER DEALINGS IN THE SOFTWARE.
 21 *
 22 * Authors: Ben Skeggs
 23 */
 24#include "bus.h"
 25
 26#ifdef CONFIG_NOUVEAU_I2C_INTERNAL
 27#define T_TIMEOUT  2200000
 28#define T_RISEFALL 1000
 29#define T_HOLD     5000
 30
 31static inline void
 32nvkm_i2c_drive_scl(struct nvkm_i2c_bus *bus, int state)
 33{
 34	bus->func->drive_scl(bus, state);
 35}
 36
 37static inline void
 38nvkm_i2c_drive_sda(struct nvkm_i2c_bus *bus, int state)
 39{
 40	bus->func->drive_sda(bus, state);
 41}
 42
 43static inline int
 44nvkm_i2c_sense_scl(struct nvkm_i2c_bus *bus)
 45{
 46	return bus->func->sense_scl(bus);
 47}
 48
 49static inline int
 50nvkm_i2c_sense_sda(struct nvkm_i2c_bus *bus)
 51{
 52	return bus->func->sense_sda(bus);
 53}
 54
 55static void
 56nvkm_i2c_delay(struct nvkm_i2c_bus *bus, u32 nsec)
 57{
 58	udelay((nsec + 500) / 1000);
 59}
 60
 61static bool
 62nvkm_i2c_raise_scl(struct nvkm_i2c_bus *bus)
 63{
 64	u32 timeout = T_TIMEOUT / T_RISEFALL;
 65
 66	nvkm_i2c_drive_scl(bus, 1);
 67	do {
 68		nvkm_i2c_delay(bus, T_RISEFALL);
 69	} while (!nvkm_i2c_sense_scl(bus) && --timeout);
 70
 71	return timeout != 0;
 72}
 73
 74static int
 75i2c_start(struct nvkm_i2c_bus *bus)
 76{
 77	int ret = 0;
 78
 79	if (!nvkm_i2c_sense_scl(bus) ||
 80	    !nvkm_i2c_sense_sda(bus)) {
 81		nvkm_i2c_drive_scl(bus, 0);
 82		nvkm_i2c_drive_sda(bus, 1);
 83		if (!nvkm_i2c_raise_scl(bus))
 84			ret = -EBUSY;
 85	}
 86
 87	nvkm_i2c_drive_sda(bus, 0);
 88	nvkm_i2c_delay(bus, T_HOLD);
 89	nvkm_i2c_drive_scl(bus, 0);
 90	nvkm_i2c_delay(bus, T_HOLD);
 91	return ret;
 92}
 93
 94static void
 95i2c_stop(struct nvkm_i2c_bus *bus)
 96{
 97	nvkm_i2c_drive_scl(bus, 0);
 98	nvkm_i2c_drive_sda(bus, 0);
 99	nvkm_i2c_delay(bus, T_RISEFALL);
100
101	nvkm_i2c_drive_scl(bus, 1);
102	nvkm_i2c_delay(bus, T_HOLD);
103	nvkm_i2c_drive_sda(bus, 1);
104	nvkm_i2c_delay(bus, T_HOLD);
105}
106
107static int
108i2c_bitw(struct nvkm_i2c_bus *bus, int sda)
109{
110	nvkm_i2c_drive_sda(bus, sda);
111	nvkm_i2c_delay(bus, T_RISEFALL);
112
113	if (!nvkm_i2c_raise_scl(bus))
114		return -ETIMEDOUT;
115	nvkm_i2c_delay(bus, T_HOLD);
116
117	nvkm_i2c_drive_scl(bus, 0);
118	nvkm_i2c_delay(bus, T_HOLD);
119	return 0;
120}
121
122static int
123i2c_bitr(struct nvkm_i2c_bus *bus)
124{
125	int sda;
126
127	nvkm_i2c_drive_sda(bus, 1);
128	nvkm_i2c_delay(bus, T_RISEFALL);
129
130	if (!nvkm_i2c_raise_scl(bus))
131		return -ETIMEDOUT;
132	nvkm_i2c_delay(bus, T_HOLD);
133
134	sda = nvkm_i2c_sense_sda(bus);
135
136	nvkm_i2c_drive_scl(bus, 0);
137	nvkm_i2c_delay(bus, T_HOLD);
138	return sda;
139}
140
141static int
142nvkm_i2c_get_byte(struct nvkm_i2c_bus *bus, u8 *byte, bool last)
143{
144	int i, bit;
145
146	*byte = 0;
147	for (i = 7; i >= 0; i--) {
148		bit = i2c_bitr(bus);
149		if (bit < 0)
150			return bit;
151		*byte |= bit << i;
152	}
153
154	return i2c_bitw(bus, last ? 1 : 0);
155}
156
157static int
158nvkm_i2c_put_byte(struct nvkm_i2c_bus *bus, u8 byte)
159{
160	int i, ret;
161	for (i = 7; i >= 0; i--) {
162		ret = i2c_bitw(bus, !!(byte & (1 << i)));
163		if (ret < 0)
164			return ret;
165	}
166
167	ret = i2c_bitr(bus);
168	if (ret == 1) /* nack */
169		ret = -EIO;
170	return ret;
171}
172
173static int
174i2c_addr(struct nvkm_i2c_bus *bus, struct i2c_msg *msg)
175{
176	u32 addr = msg->addr << 1;
177	if (msg->flags & I2C_M_RD)
178		addr |= 1;
179	return nvkm_i2c_put_byte(bus, addr);
180}
181
182int
183nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
184{
185	struct i2c_msg *msg = msgs;
186	int ret = 0, mcnt = num;
187
188	while (!ret && mcnt--) {
189		u8 remaining = msg->len;
190		u8 *ptr = msg->buf;
191
192		ret = i2c_start(bus);
193		if (ret == 0)
194			ret = i2c_addr(bus, msg);
195
196		if (msg->flags & I2C_M_RD) {
197			while (!ret && remaining--)
198				ret = nvkm_i2c_get_byte(bus, ptr++, !remaining);
199		} else {
200			while (!ret && remaining--)
201				ret = nvkm_i2c_put_byte(bus, *ptr++);
202		}
203
204		msg++;
205	}
206
207	i2c_stop(bus);
208	return (ret < 0) ? ret : num;
209}
210#else
211int
212nvkm_i2c_bit_xfer(struct nvkm_i2c_bus *bus, struct i2c_msg *msgs, int num)
213{
214	return -ENODEV;
215}
216#endif