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/display/drm_dp_helper.h>
 11#include <drm/drm.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
 19static 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
 24static 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
 36static 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
 73static 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
101ssize_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}
165EXPORT_SYMBOL_GPL(anx_dp_aux_transfer);