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Marek Vasut13082392012-08-03 17:26:10 +02001/*
2 * Copyright 2012 DENX Software Engineering, GmbH
3 *
4 * Pulled from code:
5 * Portions copyright (C) 2003 Russell King, PXA MMCI Driver
6 * Portions copyright (C) 2004-2005 Pierre Ossman, W83L51xD SD/MMC driver
7 *
8 * Copyright 2008 Embedded Alley Solutions, Inc.
9 * Copyright 2009-2011 Freescale Semiconductor, Inc.
10 *
11 * The code contained herein is licensed under the GNU General Public
12 * License. You may obtain a copy of the GNU General Public License
13 * Version 2 or later at the following locations:
14 *
15 * http://www.opensource.org/licenses/gpl-license.html
16 * http://www.gnu.org/copyleft/gpl.html
17 */
18
19#include <linux/kernel.h>
20#include <linux/init.h>
21#include <linux/clk.h>
22#include <linux/module.h>
23#include <linux/device.h>
24#include <linux/io.h>
25#include <linux/spi/mxs-spi.h>
26
27void mxs_ssp_set_clk_rate(struct mxs_ssp *ssp, unsigned int rate)
28{
29 unsigned int ssp_clk, ssp_sck;
30 u32 clock_divide, clock_rate;
31 u32 val;
32
33 ssp_clk = clk_get_rate(ssp->clk);
34
35 for (clock_divide = 2; clock_divide <= 254; clock_divide += 2) {
36 clock_rate = DIV_ROUND_UP(ssp_clk, rate * clock_divide);
37 clock_rate = (clock_rate > 0) ? clock_rate - 1 : 0;
38 if (clock_rate <= 255)
39 break;
40 }
41
42 if (clock_divide > 254) {
43 dev_err(ssp->dev,
44 "%s: cannot set clock to %d\n", __func__, rate);
45 return;
46 }
47
48 ssp_sck = ssp_clk / clock_divide / (1 + clock_rate);
49
50 val = readl(ssp->base + HW_SSP_TIMING(ssp));
51 val &= ~(BM_SSP_TIMING_CLOCK_DIVIDE | BM_SSP_TIMING_CLOCK_RATE);
52 val |= BF_SSP(clock_divide, TIMING_CLOCK_DIVIDE);
53 val |= BF_SSP(clock_rate, TIMING_CLOCK_RATE);
54 writel(val, ssp->base + HW_SSP_TIMING(ssp));
55
56 ssp->clk_rate = ssp_sck;
57
58 dev_dbg(ssp->dev,
59 "%s: clock_divide %d, clock_rate %d, ssp_clk %d, rate_actual %d, rate_requested %d\n",
60 __func__, clock_divide, clock_rate, ssp_clk, ssp_sck, rate);
61}
62EXPORT_SYMBOL_GPL(mxs_ssp_set_clk_rate);