1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright(c) 2016, Analogix Semiconductor.
4  *
5  * Based on anx7808 driver obtained from chromeos with copyright:
6  * Copyright(c) 2013, Google Inc.
7  */
8 #include <linux/regmap.h>
9 
10 #include <drm/drm.h>
11 #include <drm/dp/drm_dp_helper.h>
12 #include <drm/drm_print.h>
13 
14 #include "analogix-i2c-dptx.h"
15 
16 #define AUX_WAIT_TIMEOUT_MS	15
17 #define AUX_CH_BUFFER_SIZE	16
18 
19 static int anx_i2c_dp_clear_bits(struct regmap *map, u8 reg, u8 mask)
20 {
21 	return regmap_update_bits(map, reg, mask, 0);
22 }
23 
24 static bool anx_dp_aux_op_finished(struct regmap *map_dptx)
25 {
26 	unsigned int value;
27 	int err;
28 
29 	err = regmap_read(map_dptx, SP_DP_AUX_CH_CTRL2_REG, &value);
30 	if (err < 0)
31 		return false;
32 
33 	return (value & SP_AUX_EN) == 0;
34 }
35 
36 static int anx_dp_aux_wait(struct regmap *map_dptx)
37 {
38 	unsigned long timeout;
39 	unsigned int status;
40 	int err;
41 
42 	timeout = jiffies + msecs_to_jiffies(AUX_WAIT_TIMEOUT_MS) + 1;
43 
44 	while (!anx_dp_aux_op_finished(map_dptx)) {
45 		if (time_after(jiffies, timeout)) {
46 			if (!anx_dp_aux_op_finished(map_dptx)) {
47 				DRM_ERROR("Timed out waiting AUX to finish\n");
48 				return -ETIMEDOUT;
49 			}
50 
51 			break;
52 		}
53 
54 		usleep_range(1000, 2000);
55 	}
56 
57 	/* Read the AUX channel access status */
58 	err = regmap_read(map_dptx, SP_AUX_CH_STATUS_REG, &status);
59 	if (err < 0) {
60 		DRM_ERROR("Failed to read from AUX channel: %d\n", err);
61 		return err;
62 	}
63 
64 	if (status & SP_AUX_STATUS) {
65 		DRM_ERROR("Failed to wait for AUX channel (status: %02x)\n",
66 			  status);
67 		return -ETIMEDOUT;
68 	}
69 
70 	return 0;
71 }
72 
73 static int anx_dp_aux_address(struct regmap *map_dptx, unsigned int addr)
74 {
75 	int err;
76 
77 	err = regmap_write(map_dptx, SP_AUX_ADDR_7_0_REG, addr & 0xff);
78 	if (err)
79 		return err;
80 
81 	err = regmap_write(map_dptx, SP_AUX_ADDR_15_8_REG,
82 			   (addr & 0xff00) >> 8);
83 	if (err)
84 		return err;
85 
86 	/*
87 	 * DP AUX CH Address Register #2, only update bits[3:0]
88 	 * [7:4] RESERVED
89 	 * [3:0] AUX_ADDR[19:16], Register control AUX CH address.
90 	 */
91 	err = regmap_update_bits(map_dptx, SP_AUX_ADDR_19_16_REG,
92 				 SP_AUX_ADDR_19_16_MASK,
93 				 (addr & 0xf0000) >> 16);
94 
95 	if (err)
96 		return err;
97 
98 	return 0;
99 }
100 
101 ssize_t anx_dp_aux_transfer(struct regmap *map_dptx,
102 				struct drm_dp_aux_msg *msg)
103 {
104 	u8 ctrl1 = msg->request;
105 	u8 ctrl2 = SP_AUX_EN;
106 	u8 *buffer = msg->buffer;
107 	int err;
108 
109 	/* The DP AUX transmit and receive buffer has 16 bytes. */
110 	if (WARN_ON(msg->size > AUX_CH_BUFFER_SIZE))
111 		return -E2BIG;
112 
113 	/* Zero-sized messages specify address-only transactions. */
114 	if (msg->size < 1)
115 		ctrl2 |= SP_ADDR_ONLY;
116 	else	/* For non-zero-sized set the length field. */
117 		ctrl1 |= (msg->size - 1) << SP_AUX_LENGTH_SHIFT;
118 
119 	if ((msg->size > 0) && ((msg->request & DP_AUX_I2C_READ) == 0)) {
120 		/* When WRITE | MOT write values to data buffer */
121 		err = regmap_bulk_write(map_dptx,
122 					SP_DP_BUF_DATA0_REG, buffer,
123 					msg->size);
124 		if (err)
125 			return err;
126 	}
127 
128 	/* Write address and request */
129 	err = anx_dp_aux_address(map_dptx, msg->address);
130 	if (err)
131 		return err;
132 
133 	err = regmap_write(map_dptx, SP_DP_AUX_CH_CTRL1_REG, ctrl1);
134 	if (err)
135 		return err;
136 
137 	/* Start transaction */
138 	err = regmap_update_bits(map_dptx, SP_DP_AUX_CH_CTRL2_REG,
139 				 SP_ADDR_ONLY | SP_AUX_EN, ctrl2);
140 	if (err)
141 		return err;
142 
143 	err = anx_dp_aux_wait(map_dptx);
144 	if (err)
145 		return err;
146 
147 	msg->reply = DP_AUX_I2C_REPLY_ACK;
148 
149 	if ((msg->size > 0) && (msg->request & DP_AUX_I2C_READ)) {
150 		/* Read values from data buffer */
151 		err = regmap_bulk_read(map_dptx,
152 				       SP_DP_BUF_DATA0_REG, buffer,
153 				       msg->size);
154 		if (err)
155 			return err;
156 	}
157 
158 	err = anx_i2c_dp_clear_bits(map_dptx, SP_DP_AUX_CH_CTRL2_REG,
159 				    SP_ADDR_ONLY);
160 	if (err)
161 		return err;
162 
163 	return msg->size;
164 }
165 EXPORT_SYMBOL_GPL(anx_dp_aux_transfer);
166