aemif.c

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/*
 * AEMIF support for DaVinci SoCs
 *
 * Copyright (C) 2010 Texas Instruments Incorporated. http://www.ti.com/
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 */

#include <linux/kernel.h>
#include <linux/io.h>
#include <linux/err.h>
#include <linux/clk.h>
#include <linux/module.h>
#include <linux/time.h>

#include <linux/platform_data/mtd-davinci-aemif.h>

/* Timing value configuration */

#define TA(x)       ((x) << 2)
#define RHOLD(x)    ((x) << 4)
#define RSTROBE(x)  ((x) << 7)
#define RSETUP(x)   ((x) << 13)
#define WHOLD(x)    ((x) << 17)
#define WSTROBE(x)  ((x) << 20)
#define WSETUP(x)   ((x) << 26)

#define TA_MAX      0x3
#define RHOLD_MAX   0x7
#define RSTROBE_MAX 0x3f
#define RSETUP_MAX  0xf
#define WHOLD_MAX   0x7
#define WSTROBE_MAX 0x3f
#define WSETUP_MAX  0xf

#define TIMING_MASK (TA(TA_MAX) | \
                RHOLD(RHOLD_MAX) | \
                RSTROBE(RSTROBE_MAX) |  \
                RSETUP(RSETUP_MAX) | \
                WHOLD(WHOLD_MAX) | \
                WSTROBE(WSTROBE_MAX) | \
                WSETUP(WSETUP_MAX))

/*
 * aemif_calc_rate - calculate timing data.
 * @wanted: The cycle time needed in nanoseconds.
 * @clk: The input clock rate in kHz.
 * @max: The maximum divider value that can be programmed.
 *
 * On success, returns the calculated timing value minus 1 for easy
 * programming into AEMIF timing registers, else negative errno.
 */
static int aemif_calc_rate(int wanted, unsigned long clk, int max)
{
    int result;

    result = DIV_ROUND_UP((wanted * clk), NSEC_PER_MSEC) - 1;

    pr_debug("%s: result %d from %ld, %d\n", __func__, result, clk, wanted);

    /* It is generally OK to have a more relaxed timing than requested... */
    if (result < 0)
        result = 0;

    /* ... But configuring tighter timings is not an option. */
    else if (result > max)
        result = -EINVAL;

    return result;
}

int davinci_aemif_setup_timing(struct davinci_aemif_timing *t,
                    void __iomem *base, unsigned cs)
{
    unsigned set, val;
    int ta, rhold, rstrobe, rsetup, whold, wstrobe, wsetup;
    unsigned offset = A1CR_OFFSET + cs * 4;
    struct clk *aemif_clk;
    unsigned long clkrate;

    if (!t)
        return 0;   /* Nothing to do */

    aemif_clk = clk_get(NULL, "aemif");
    if (IS_ERR(aemif_clk))
        return PTR_ERR(aemif_clk);

    clkrate = clk_get_rate(aemif_clk);

    clkrate /= 1000;    /* turn clock into kHz for ease of use */

    ta  = aemif_calc_rate(t->ta, clkrate, TA_MAX);
    rhold   = aemif_calc_rate(t->rhold, clkrate, RHOLD_MAX);
    rstrobe = aemif_calc_rate(t->rstrobe, clkrate, RSTROBE_MAX);
    rsetup  = aemif_calc_rate(t->rsetup, clkrate, RSETUP_MAX);
    whold   = aemif_calc_rate(t->whold, clkrate, WHOLD_MAX);
    wstrobe = aemif_calc_rate(t->wstrobe, clkrate, WSTROBE_MAX);
    wsetup  = aemif_calc_rate(t->wsetup, clkrate, WSETUP_MAX);

    if (ta < 0 || rhold < 0 || rstrobe < 0 || rsetup < 0 ||
            whold < 0 || wstrobe < 0 || wsetup < 0) {
        pr_err("%s: cannot get suitable timings\n", __func__);
        return -EINVAL;
    }

    set = TA(ta) | RHOLD(rhold) | RSTROBE(rstrobe) | RSETUP(rsetup) |
        WHOLD(whold) | WSTROBE(wstrobe) | WSETUP(wsetup);

    val = __raw_readl(base + offset);
    val &= ~TIMING_MASK;
    val |= set;
    __raw_writel(val, base + offset);

    return 0;
}
EXPORT_SYMBOL(davinci_aemif_setup_timing);