1 /* 2 * SPI master driver for ICP DAS LP-8841 RTC 3 * 4 * Copyright (C) 2016 Sergei Ianovich 5 * 6 * based on 7 * 8 * Dallas DS1302 RTC Support 9 * Copyright (C) 2002 David McCullough 10 * Copyright (C) 2003 - 2007 Paul Mundt 11 * 12 * This program is free software; you can redistribute it and/or modify 13 * it under the terms of the GNU General Public License as published by 14 * the Free Software Foundation; either version 2 of the License, or 15 * (at your option) any later version. 16 * 17 * This program is distributed in the hope that it will be useful, 18 * but WITHOUT ANY WARRANTY; without even the implied warranty of 19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 20 * GNU General Public License for more details. 21 */ 22 #include <linux/delay.h> 23 #include <linux/kernel.h> 24 #include <linux/module.h> 25 #include <linux/platform_device.h> 26 #include <linux/of.h> 27 #include <linux/of_device.h> 28 #include <linux/spi/spi.h> 29 30 #define DRIVER_NAME "spi_lp8841_rtc" 31 32 #define SPI_LP8841_RTC_CE 0x01 33 #define SPI_LP8841_RTC_CLK 0x02 34 #define SPI_LP8841_RTC_nWE 0x04 35 #define SPI_LP8841_RTC_MOSI 0x08 36 #define SPI_LP8841_RTC_MISO 0x01 37 38 /* 39 * REVISIT If there is support for SPI_3WIRE and SPI_LSB_FIRST in SPI 40 * GPIO driver, this SPI driver can be replaced by a simple GPIO driver 41 * providing 3 GPIO pins. 42 */ 43 44 struct spi_lp8841_rtc { 45 void *iomem; 46 unsigned long state; 47 }; 48 49 static inline void 50 setsck(struct spi_lp8841_rtc *data, int is_on) 51 { 52 if (is_on) 53 data->state |= SPI_LP8841_RTC_CLK; 54 else 55 data->state &= ~SPI_LP8841_RTC_CLK; 56 writeb(data->state, data->iomem); 57 } 58 59 static inline void 60 setmosi(struct spi_lp8841_rtc *data, int is_on) 61 { 62 if (is_on) 63 data->state |= SPI_LP8841_RTC_MOSI; 64 else 65 data->state &= ~SPI_LP8841_RTC_MOSI; 66 writeb(data->state, data->iomem); 67 } 68 69 static inline int 70 getmiso(struct spi_lp8841_rtc *data) 71 { 72 return ioread8(data->iomem) & SPI_LP8841_RTC_MISO; 73 } 74 75 static inline u32 76 bitbang_txrx_be_cpha0_lsb(struct spi_lp8841_rtc *data, 77 unsigned usecs, unsigned cpol, unsigned flags, 78 u32 word, u8 bits) 79 { 80 /* if (cpol == 0) this is SPI_MODE_0; else this is SPI_MODE_2 */ 81 82 u32 shift = 32 - bits; 83 /* clock starts at inactive polarity */ 84 for (; likely(bits); bits--) { 85 86 /* setup LSB (to slave) on leading edge */ 87 if ((flags & SPI_MASTER_NO_TX) == 0) 88 setmosi(data, (word & 1)); 89 90 usleep_range(usecs, usecs + 1); /* T(setup) */ 91 92 /* sample LSB (from slave) on trailing edge */ 93 word >>= 1; 94 if ((flags & SPI_MASTER_NO_RX) == 0) 95 word |= (getmiso(data) << 31); 96 97 setsck(data, !cpol); 98 usleep_range(usecs, usecs + 1); 99 100 setsck(data, cpol); 101 } 102 103 word >>= shift; 104 return word; 105 } 106 107 static int 108 spi_lp8841_rtc_transfer_one(struct spi_master *master, 109 struct spi_device *spi, 110 struct spi_transfer *t) 111 { 112 struct spi_lp8841_rtc *data = spi_master_get_devdata(master); 113 unsigned count = t->len; 114 const u8 *tx = t->tx_buf; 115 u8 *rx = t->rx_buf; 116 u8 word = 0; 117 int ret = 0; 118 119 if (tx) { 120 data->state &= ~SPI_LP8841_RTC_nWE; 121 writeb(data->state, data->iomem); 122 while (likely(count > 0)) { 123 word = *tx++; 124 bitbang_txrx_be_cpha0_lsb(data, 1, 0, 125 SPI_MASTER_NO_RX, word, 8); 126 count--; 127 } 128 } else if (rx) { 129 data->state |= SPI_LP8841_RTC_nWE; 130 writeb(data->state, data->iomem); 131 while (likely(count > 0)) { 132 word = bitbang_txrx_be_cpha0_lsb(data, 1, 0, 133 SPI_MASTER_NO_TX, word, 8); 134 *rx++ = word; 135 count--; 136 } 137 } else { 138 ret = -EINVAL; 139 } 140 141 spi_finalize_current_transfer(master); 142 143 return ret; 144 } 145 146 static void 147 spi_lp8841_rtc_set_cs(struct spi_device *spi, bool enable) 148 { 149 struct spi_lp8841_rtc *data = spi_master_get_devdata(spi->master); 150 151 data->state = 0; 152 writeb(data->state, data->iomem); 153 if (enable) { 154 usleep_range(4, 5); 155 data->state |= SPI_LP8841_RTC_CE; 156 writeb(data->state, data->iomem); 157 usleep_range(4, 5); 158 } 159 } 160 161 static int 162 spi_lp8841_rtc_setup(struct spi_device *spi) 163 { 164 if ((spi->mode & SPI_CS_HIGH) == 0) { 165 dev_err(&spi->dev, "unsupported active low chip select\n"); 166 return -EINVAL; 167 } 168 169 if ((spi->mode & SPI_LSB_FIRST) == 0) { 170 dev_err(&spi->dev, "unsupported MSB first mode\n"); 171 return -EINVAL; 172 } 173 174 if ((spi->mode & SPI_3WIRE) == 0) { 175 dev_err(&spi->dev, "unsupported wiring. 3 wires required\n"); 176 return -EINVAL; 177 } 178 179 return 0; 180 } 181 182 #ifdef CONFIG_OF 183 static const struct of_device_id spi_lp8841_rtc_dt_ids[] = { 184 { .compatible = "icpdas,lp8841-spi-rtc" }, 185 { } 186 }; 187 188 MODULE_DEVICE_TABLE(of, spi_lp8841_rtc_dt_ids); 189 #endif 190 191 static int 192 spi_lp8841_rtc_probe(struct platform_device *pdev) 193 { 194 int ret; 195 struct spi_master *master; 196 struct spi_lp8841_rtc *data; 197 void *iomem; 198 199 master = spi_alloc_master(&pdev->dev, sizeof(*data)); 200 if (!master) 201 return -ENOMEM; 202 platform_set_drvdata(pdev, master); 203 204 master->flags = SPI_MASTER_HALF_DUPLEX; 205 master->mode_bits = SPI_CS_HIGH | SPI_3WIRE | SPI_LSB_FIRST; 206 207 master->bus_num = pdev->id; 208 master->num_chipselect = 1; 209 master->setup = spi_lp8841_rtc_setup; 210 master->set_cs = spi_lp8841_rtc_set_cs; 211 master->transfer_one = spi_lp8841_rtc_transfer_one; 212 master->bits_per_word_mask = SPI_BPW_MASK(8); 213 #ifdef CONFIG_OF 214 master->dev.of_node = pdev->dev.of_node; 215 #endif 216 217 data = spi_master_get_devdata(master); 218 219 iomem = platform_get_resource(pdev, IORESOURCE_MEM, 0); 220 data->iomem = devm_ioremap_resource(&pdev->dev, iomem); 221 ret = PTR_ERR_OR_ZERO(data->iomem); 222 if (ret) { 223 dev_err(&pdev->dev, "failed to get IO address\n"); 224 goto err_put_master; 225 } 226 227 /* register with the SPI framework */ 228 ret = devm_spi_register_master(&pdev->dev, master); 229 if (ret) { 230 dev_err(&pdev->dev, "cannot register spi master\n"); 231 goto err_put_master; 232 } 233 234 return ret; 235 236 237 err_put_master: 238 spi_master_put(master); 239 240 return ret; 241 } 242 243 MODULE_ALIAS("platform:" DRIVER_NAME); 244 245 static struct platform_driver spi_lp8841_rtc_driver = { 246 .driver = { 247 .name = DRIVER_NAME, 248 .of_match_table = of_match_ptr(spi_lp8841_rtc_dt_ids), 249 }, 250 .probe = spi_lp8841_rtc_probe, 251 }; 252 module_platform_driver(spi_lp8841_rtc_driver); 253 254 MODULE_DESCRIPTION("SPI master driver for ICP DAS LP-8841 RTC"); 255 MODULE_AUTHOR("Sergei Ianovich"); 256 MODULE_LICENSE("GPL"); 257