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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 <mach/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;
}
/**
* davinci_aemif_setup_timing - setup timing values for a given AEMIF interface
* @t: timing values to be progammed
* @base: The virtual base address of the AEMIF interface
* @cs: chip-select to program the timing values for
*
* This function programs the given timing values (in real clock) into the
* AEMIF registers taking the AEMIF clock into account.
*
* This function does not use any locking while programming the AEMIF
* because it is expected that there is only one user of a given
* chip-select.
*
* Returns 0 on success, else negative errno.
*/
int davinci_aemif_setup_timing(struct davinci_aemif_timing *t,
void __iomem *base, unsigned cs)
{
unsigned set, val;
unsigned 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);
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