arch/arm/mach-davinci/aemif.c

   1 /*
   2  * AEMIF support for DaVinci SoCs
   3  *
   4  * Copyright (C) 2010 Texas Instruments Incorporated. http://www.ti.com/
   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
  11 #include <linux/kernel.h>
  12 #include <linux/io.h>
  13 #include <linux/err.h>
  14 #include <linux/clk.h>
  15 #include <linux/module.h>
  16 #include <linux/time.h>
  17
  18 #include <mach/aemif.h>
  19
  20 /* Timing value configuration */
  21
  22 #define TA(x)           ((x) << 2)
  23 #define RHOLD(x)        ((x) << 4)
  24 #define RSTROBE(x)      ((x) << 7)
  25 #define RSETUP(x)       ((x) << 13)
  26 #define WHOLD(x)        ((x) << 17)
  27 #define WSTROBE(x)      ((x) << 20)
  28 #define WSETUP(x)       ((x) << 26)
  29
  30 #define TA_MAX          0x3
  31 #define RHOLD_MAX       0x7
  32 #define RSTROBE_MAX     0x3f
  33 #define RSETUP_MAX      0xf
  34 #define WHOLD_MAX       0x7
  35 #define WSTROBE_MAX     0x3f
  36 #define WSETUP_MAX      0xf
  37
  38 #define TIMING_MASK     (TA(TA_MAX) | \
  39                                 RHOLD(RHOLD_MAX) | \
  40                                 RSTROBE(RSTROBE_MAX) |  \
  41                                 RSETUP(RSETUP_MAX) | \
  42                                 WHOLD(WHOLD_MAX) | \
  43                                 WSTROBE(WSTROBE_MAX) | \
  44                                 WSETUP(WSETUP_MAX))
  45
  46 /*
  47  * aemif_calc_rate - calculate timing data.
  48  * @wanted: The cycle time needed in nanoseconds.
  49  * @clk: The input clock rate in kHz.
  50  * @max: The maximum divider value that can be programmed.
  51  *
  52  * On success, returns the calculated timing value minus 1 for easy
  53  * programming into AEMIF timing registers, else negative errno.
  54  */
  55 static int aemif_calc_rate(int wanted, unsigned long clk, int max)
  56 {
  57         int result;
  58
  59         result = DIV_ROUND_UP((wanted * clk), NSEC_PER_MSEC) - 1;
  60
  61         pr_debug("%s: result %d from %ld, %d\n", __func__, result, clk, wanted);
  62
  63         /* It is generally OK to have a more relaxed timing than requested... */
  64         if (result < 0)
  65                 result = 0;
  66
  67         /* ... But configuring tighter timings is not an option. */
  68         else if (result > max)
  69                 result = -EINVAL;
  70
  71         return result;
  72 }
  73
  74 /**
  75  * davinci_aemif_setup_timing - setup timing values for a given AEMIF interface
  76  * @t: timing values to be progammed
  77  * @base: The virtual base address of the AEMIF interface
  78  * @cs: chip-select to program the timing values for
  79  *
  80  * This function programs the given timing values (in real clock) into the
  81  * AEMIF registers taking the AEMIF clock into account.
  82  *
  83  * This function does not use any locking while programming the AEMIF
  84  * because it is expected that there is only one user of a given
  85  * chip-select.
  86  *
  87  * Returns 0 on success, else negative errno.
  88  */
  89 int davinci_aemif_setup_timing(struct davinci_aemif_timing *t,
  90                                         void __iomem *base, unsigned cs)
  91 {
  92         unsigned set, val;
  93         int ta, rhold, rstrobe, rsetup, whold, wstrobe, wsetup;
  94         unsigned offset = A1CR_OFFSET + cs * 4;
  95         struct clk *aemif_clk;
  96         unsigned long clkrate;
  97
  98         if (!t)
  99                 return 0;       /* Nothing to do */
 100
 101         aemif_clk = clk_get(NULL, "aemif");
 102         if (IS_ERR(aemif_clk))
 103                 return PTR_ERR(aemif_clk);
 104
 105         clkrate = clk_get_rate(aemif_clk);
 106
 107         clkrate /= 1000;        /* turn clock into kHz for ease of use */
 108
 109         ta      = aemif_calc_rate(t->ta, clkrate, TA_MAX);
 110         rhold   = aemif_calc_rate(t->rhold, clkrate, RHOLD_MAX);
 111         rstrobe = aemif_calc_rate(t->rstrobe, clkrate, RSTROBE_MAX);
 112         rsetup  = aemif_calc_rate(t->rsetup, clkrate, RSETUP_MAX);
 113         whold   = aemif_calc_rate(t->whold, clkrate, WHOLD_MAX);
 114         wstrobe = aemif_calc_rate(t->wstrobe, clkrate, WSTROBE_MAX);
 115         wsetup  = aemif_calc_rate(t->wsetup, clkrate, WSETUP_MAX);
 116
 117         if (ta < 0 || rhold < 0 || rstrobe < 0 || rsetup < 0 ||
 118                         whold < 0 || wstrobe < 0 || wsetup < 0) {
 119                 pr_err("%s: cannot get suitable timings\n", __func__);
 120                 return -EINVAL;
 121         }
 122
 123         set = TA(ta) | RHOLD(rhold) | RSTROBE(rstrobe) | RSETUP(rsetup) |
 124                 WHOLD(whold) | WSTROBE(wstrobe) | WSETUP(wsetup);
 125
 126         val = __raw_readl(base + offset);
 127         val &= ~TIMING_MASK;
 128         val |= set;
 129         __raw_writel(val, base + offset);
 130
 131         return 0;
 132 }
 133 EXPORT_SYMBOL(davinci_aemif_setup_timing);