arch/arm/mach-sa1100/ssp.c

   1 /*
   2  *  linux/arch/arm/mach-sa1100/ssp.c
   3  *
   4  *  Copyright (C) 2003 Russell King.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  *
  10  *  Generic SSP driver.  This provides the generic core for simple
  11  *  IO-based SSP applications.
  12  */
  13 #include <linux/module.h>
  14 #include <linux/kernel.h>
  15 #include <linux/sched.h>
  16 #include <linux/errno.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/ioport.h>
  19 #include <linux/init.h>
  20
  21 #include <asm/io.h>
  22 #include <asm/irq.h>
  23 #include <asm/hardware.h>
  24 #include <asm/hardware/ssp.h>
  25
  26 #define TIMEOUT 100000
  27
  28 static irqreturn_t ssp_interrupt(int irq, void *dev_id)
  29 {
  30         unsigned int status = Ser4SSSR;
  31
  32         if (status & SSSR_ROR)
  33                 printk(KERN_WARNING "SSP: receiver overrun\n");
  34
  35         Ser4SSSR = SSSR_ROR;
  36
  37         return status ? IRQ_HANDLED : IRQ_NONE;
  38 }
  39
  40 /**
  41  * ssp_write_word - write a word to the SSP port
  42  * @data: 16-bit, MSB justified data to write.
  43  *
  44  * Wait for a free entry in the SSP transmit FIFO, and write a data
  45  * word to the SSP port.  Wait for the SSP port to start sending
  46  * the data.
  47  *
  48  * The caller is expected to perform the necessary locking.
  49  *
  50  * Returns:
  51  *   %-ETIMEDOUT        timeout occurred
  52  *   0                  success
  53  */
  54 int ssp_write_word(u16 data)
  55 {
  56         int timeout = TIMEOUT;
  57
  58         while (!(Ser4SSSR & SSSR_TNF)) {
  59                 if (!--timeout)
  60                         return -ETIMEDOUT;
  61                 cpu_relax();
  62         }
  63
  64         Ser4SSDR = data;
  65
  66         timeout = TIMEOUT;
  67         while (!(Ser4SSSR & SSSR_BSY)) {
  68                 if (!--timeout)
  69                         return -ETIMEDOUT;
  70                 cpu_relax();
  71         }
  72
  73         return 0;
  74 }
  75
  76 /**
  77  * ssp_read_word - read a word from the SSP port
  78  *
  79  * Wait for a data word in the SSP receive FIFO, and return the
  80  * received data.  Data is LSB justified.
  81  *
  82  * Note: Currently, if data is not expected to be received, this
  83  * function will wait for ever.
  84  *
  85  * The caller is expected to perform the necessary locking.
  86  *
  87  * Returns:
  88  *   %-ETIMEDOUT        timeout occurred
  89  *   16-bit data        success
  90  */
  91 int ssp_read_word(u16 *data)
  92 {
  93         int timeout = TIMEOUT;
  94
  95         while (!(Ser4SSSR & SSSR_RNE)) {
  96                 if (!--timeout)
  97                         return -ETIMEDOUT;
  98                 cpu_relax();
  99         }
 100
 101         *data = (u16)Ser4SSDR;
 102
 103         return 0;
 104 }
 105
 106 /**
 107  * ssp_flush - flush the transmit and receive FIFOs
 108  *
 109  * Wait for the SSP to idle, and ensure that the receive FIFO
 110  * is empty.
 111  *
 112  * The caller is expected to perform the necessary locking.
 113  *
 114  * Returns:
 115  *   %-ETIMEDOUT        timeout occurred
 116  *   0                  success
 117  */
 118 int ssp_flush(void)
 119 {
 120         int timeout = TIMEOUT * 2;
 121
 122         do {
 123                 while (Ser4SSSR & SSSR_RNE) {
 124                         if (!--timeout)
 125                                 return -ETIMEDOUT;
 126                         (void) Ser4SSDR;
 127                 }
 128                 if (!--timeout)
 129                         return -ETIMEDOUT;
 130         } while (Ser4SSSR & SSSR_BSY);
 131
 132         return 0;
 133 }
 134
 135 /**
 136  * ssp_enable - enable the SSP port
 137  *
 138  * Turn on the SSP port.
 139  */
 140 void ssp_enable(void)
 141 {
 142         Ser4SSCR0 |= SSCR0_SSE;
 143 }
 144
 145 /**
 146  * ssp_disable - shut down the SSP port
 147  *
 148  * Turn off the SSP port, optionally powering it down.
 149  */
 150 void ssp_disable(void)
 151 {
 152         Ser4SSCR0 &= ~SSCR0_SSE;
 153 }
 154
 155 /**
 156  * ssp_save_state - save the SSP configuration
 157  * @ssp: pointer to structure to save SSP configuration
 158  *
 159  * Save the configured SSP state for suspend.
 160  */
 161 void ssp_save_state(struct ssp_state *ssp)
 162 {
 163         ssp->cr0 = Ser4SSCR0;
 164         ssp->cr1 = Ser4SSCR1;
 165
 166         Ser4SSCR0 &= ~SSCR0_SSE;
 167 }
 168
 169 /**
 170  * ssp_restore_state - restore a previously saved SSP configuration
 171  * @ssp: pointer to configuration saved by ssp_save_state
 172  *
 173  * Restore the SSP configuration saved previously by ssp_save_state.
 174  */
 175 void ssp_restore_state(struct ssp_state *ssp)
 176 {
 177         Ser4SSSR = SSSR_ROR;
 178
 179         Ser4SSCR0 = ssp->cr0 & ~SSCR0_SSE;
 180         Ser4SSCR1 = ssp->cr1;
 181         Ser4SSCR0 = ssp->cr0;
 182 }
 183
 184 /**
 185  * ssp_init - setup the SSP port
 186  *
 187  * initialise and claim resources for the SSP port.
 188  *
 189  * Returns:
 190  *   %-ENODEV   if the SSP port is unavailable
 191  *   %-EBUSY    if the resources are already in use
 192  *   %0         on success
 193  */
 194 int ssp_init(void)
 195 {
 196         int ret;
 197
 198         if (!(PPAR & PPAR_SPR) && (Ser4MCCR0 & MCCR0_MCE))
 199                 return -ENODEV;
 200
 201         if (!request_mem_region(__PREG(Ser4SSCR0), 0x18, "SSP")) {
 202                 return -EBUSY;
 203         }
 204
 205         Ser4SSSR = SSSR_ROR;
 206
 207         ret = request_irq(IRQ_Ser4SSP, ssp_interrupt, 0, "SSP", NULL);
 208         if (ret)
 209                 goto out_region;
 210
 211         return 0;
 212
 213  out_region:
 214         release_mem_region(__PREG(Ser4SSCR0), 0x18);
 215         return ret;
 216 }
 217
 218 /**
 219  * ssp_exit - undo the effects of ssp_init
 220  *
 221  * release and free resources for the SSP port.
 222  */
 223 void ssp_exit(void)
 224 {
 225         Ser4SSCR0 &= ~SSCR0_SSE;
 226
 227         free_irq(IRQ_Ser4SSP, NULL);
 228         release_mem_region(__PREG(Ser4SSCR0), 0x18);
 229 }
 230
 231 MODULE_AUTHOR("Russell King");
 232 MODULE_DESCRIPTION("SA11x0 SSP PIO driver");
 233 MODULE_LICENSE("GPL");
 234
 235 EXPORT_SYMBOL(ssp_write_word);
 236 EXPORT_SYMBOL(ssp_read_word);
 237 EXPORT_SYMBOL(ssp_flush);
 238 EXPORT_SYMBOL(ssp_enable);
 239 EXPORT_SYMBOL(ssp_disable);
 240 EXPORT_SYMBOL(ssp_save_state);
 241 EXPORT_SYMBOL(ssp_restore_state);
 242 EXPORT_SYMBOL(ssp_init);
 243 EXPORT_SYMBOL(ssp_exit);