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1// SPDX-License-Identifier: GPL-2.0-or-later2/*3 * SPI host driver for ICP DAS LP-8841 RTC4 *5 * Copyright (C) 2016 Sergei Ianovich6 *7 * based on8 *9 * Dallas DS1302 RTC Support10 * Copyright (C) 2002 David McCullough11 * Copyright (C) 2003 - 2007 Paul Mundt12 */13#include <linux/delay.h>14#include <linux/kernel.h>15#include <linux/module.h>16#include <linux/platform_device.h>17#include <linux/of.h>18#include <linux/spi/spi.h>19 20#define DRIVER_NAME "spi_lp8841_rtc"21 22#define SPI_LP8841_RTC_CE 0x0123#define SPI_LP8841_RTC_CLK 0x0224#define SPI_LP8841_RTC_nWE 0x0425#define SPI_LP8841_RTC_MOSI 0x0826#define SPI_LP8841_RTC_MISO 0x0127 28/*29 * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI30 * GPIO driver, this SPI driver can be replaced by a simple GPIO driver31 * providing 3 GPIO pins.32 */33 34struct spi_lp8841_rtc {35 void *iomem;36 unsigned long state;37};38 39static inline void40setsck(struct spi_lp8841_rtc *data, int is_on)41{42 if (is_on)43 data->state |= SPI_LP8841_RTC_CLK;44 else45 data->state &= ~SPI_LP8841_RTC_CLK;46 writeb(data->state, data->iomem);47}48 49static inline void50setmosi(struct spi_lp8841_rtc *data, int is_on)51{52 if (is_on)53 data->state |= SPI_LP8841_RTC_MOSI;54 else55 data->state &= ~SPI_LP8841_RTC_MOSI;56 writeb(data->state, data->iomem);57}58 59static inline int60getmiso(struct spi_lp8841_rtc *data)61{62 return ioread8(data->iomem) & SPI_LP8841_RTC_MISO;63}64 65static inline u3266bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data,67 unsigned usecs, unsigned cpol, unsigned flags,68 u32 word, u8 bits)69{70 /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */71 72 u32 shift = 32 - bits;73 /* clock starts at inactive polarity */74 for (; likely(bits); bits--) {75 76 /* setup LSB (to target) on leading edge */77 if ((flags & SPI_CONTROLLER_NO_TX) == 0)78 setmosi(data, (word & 1));79 80 usleep_range(usecs, usecs + 1); /* T(setup) */81 82 /* sample LSB (from target) on trailing edge */83 word >>= 1;84 if ((flags & SPI_CONTROLLER_NO_RX) == 0)85 word |= (getmiso(data) << 31);86 87 setsck(data, !cpol);88 usleep_range(usecs, usecs + 1);89 90 setsck(data, cpol);91 }92 93 word >>= shift;94 return word;95}96 97static int98spi_lp8841_rtc_transfer_one(struct spi_controller *host,99 struct spi_device *spi,100 struct spi_transfer *t)101{102 struct spi_lp8841_rtc *data = spi_controller_get_devdata(host);103 unsigned count = t->len;104 const u8 *tx = t->tx_buf;105 u8 *rx = t->rx_buf;106 u8 word = 0;107 int ret = 0;108 109 if (tx) {110 data->state &= ~SPI_LP8841_RTC_nWE;111 writeb(data->state, data->iomem);112 while (likely(count > 0)) {113 word = *tx++;114 bitbang_txrx_be_cpha0_lsb(data, 1, 0,115 SPI_CONTROLLER_NO_RX, word, 8);116 count--;117 }118 } else if (rx) {119 data->state |= SPI_LP8841_RTC_nWE;120 writeb(data->state, data->iomem);121 while (likely(count > 0)) {122 word = bitbang_txrx_be_cpha0_lsb(data, 1, 0,123 SPI_CONTROLLER_NO_TX, word, 8);124 *rx++ = word;125 count--;126 }127 } else {128 ret = -EINVAL;129 }130 131 spi_finalize_current_transfer(host);132 133 return ret;134}135 136static void137spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable)138{139 struct spi_lp8841_rtc *data = spi_controller_get_devdata(spi->controller);140 141 data->state = 0;142 writeb(data->state, data->iomem);143 if (enable) {144 usleep_range(4, 5);145 data->state |= SPI_LP8841_RTC_CE;146 writeb(data->state, data->iomem);147 usleep_range(4, 5);148 }149}150 151static int152spi_lp8841_rtc_setup(struct spi_device *spi)153{154 if ((spi->mode & SPI_CS_HIGH) == 0) {155 dev_err(&spi->dev, "unsupported active low chip select\n");156 return -EINVAL;157 }158 159 if ((spi->mode & SPI_LSB_FIRST) == 0) {160 dev_err(&spi->dev, "unsupported MSB first mode\n");161 return -EINVAL;162 }163 164 if ((spi->mode & SPI_3WIRE) == 0) {165 dev_err(&spi->dev, "unsupported wiring. 3 wires required\n");166 return -EINVAL;167 }168 169 return 0;170}171 172#ifdef CONFIG_OF173static const struct of_device_id spi_lp8841_rtc_dt_ids[] = {174 { .compatible = "icpdas,lp8841-spi-rtc" },175 { }176};177 178MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids);179#endif180 181static int182spi_lp8841_rtc_probe(struct platform_device *pdev)183{184 int ret;185 struct spi_controller *host;186 struct spi_lp8841_rtc *data;187 188 host = spi_alloc_host(&pdev->dev, sizeof(*data));189 if (!host)190 return -ENOMEM;191 platform_set_drvdata(pdev, host);192 193 host->flags = SPI_CONTROLLER_HALF_DUPLEX;194 host->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST;195 196 host->bus_num = pdev->id;197 host->num_chipselect = 1;198 host->setup = spi_lp8841_rtc_setup;199 host->set_cs = spi_lp8841_rtc_set_cs;200 host->transfer_one = spi_lp8841_rtc_transfer_one;201 host->bits_per_word_mask = SPI_BPW_MASK(8);202#ifdef CONFIG_OF203 host->dev.of_node = pdev->dev.of_node;204#endif205 206 data = spi_controller_get_devdata(host);207 208 data->iomem = devm_platform_ioremap_resource(pdev, 0);209 ret = PTR_ERR_OR_ZERO(data->iomem);210 if (ret) {211 dev_err(&pdev->dev, "failed to get IO address\n");212 goto err_put_host;213 }214 215 /* register with the SPI framework */216 ret = devm_spi_register_controller(&pdev->dev, host);217 if (ret) {218 dev_err(&pdev->dev, "cannot register spi host\n");219 goto err_put_host;220 }221 222 return ret;223 224 225err_put_host:226 spi_controller_put(host);227 228 return ret;229}230 231MODULE_ALIAS("platform:" DRIVER_NAME);232 233static struct platform_driver spi_lp8841_rtc_driver = {234 .driver = {235 .name = DRIVER_NAME,236 .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids),237 },238 .probe = spi_lp8841_rtc_probe,239};240module_platform_driver(spi_lp8841_rtc_driver);241 242MODULE_DESCRIPTION("SPI host driver for ICP DAS LP-8841 RTC");243MODULE_AUTHOR("Sergei Ianovich");244MODULE_LICENSE("GPL");245