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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 | unsigned 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); |
134 |
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