63 строки
1.8 KiB
C
63 строки
1.8 KiB
C
/*
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* Copyright 2012 DENX Software Engineering, GmbH
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*
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* Pulled from code:
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* Portions copyright (C) 2003 Russell King, PXA MMCI Driver
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* Portions copyright (C) 2004-2005 Pierre Ossman, W83L51xD SD/MMC driver
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*
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* Copyright 2008 Embedded Alley Solutions, Inc.
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* Copyright 2009-2011 Freescale Semiconductor, Inc.
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*
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* The code contained herein is licensed under the GNU General Public
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* License. You may obtain a copy of the GNU General Public License
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* Version 2 or later at the following locations:
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*
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* http://www.opensource.org/licenses/gpl-license.html
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* http://www.gnu.org/copyleft/gpl.html
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*/
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/clk.h>
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#include <linux/module.h>
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#include <linux/device.h>
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#include <linux/io.h>
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#include <linux/spi/mxs-spi.h>
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void mxs_ssp_set_clk_rate(struct mxs_ssp *ssp, unsigned int rate)
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{
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unsigned int ssp_clk, ssp_sck;
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u32 clock_divide, clock_rate;
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u32 val;
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ssp_clk = clk_get_rate(ssp->clk);
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for (clock_divide = 2; clock_divide <= 254; clock_divide += 2) {
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clock_rate = DIV_ROUND_UP(ssp_clk, rate * clock_divide);
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clock_rate = (clock_rate > 0) ? clock_rate - 1 : 0;
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if (clock_rate <= 255)
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break;
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}
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if (clock_divide > 254) {
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dev_err(ssp->dev,
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"%s: cannot set clock to %d\n", __func__, rate);
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return;
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}
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ssp_sck = ssp_clk / clock_divide / (1 + clock_rate);
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val = readl(ssp->base + HW_SSP_TIMING(ssp));
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val &= ~(BM_SSP_TIMING_CLOCK_DIVIDE | BM_SSP_TIMING_CLOCK_RATE);
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val |= BF_SSP(clock_divide, TIMING_CLOCK_DIVIDE);
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val |= BF_SSP(clock_rate, TIMING_CLOCK_RATE);
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writel(val, ssp->base + HW_SSP_TIMING(ssp));
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ssp->clk_rate = ssp_sck;
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dev_dbg(ssp->dev,
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"%s: clock_divide %d, clock_rate %d, ssp_clk %d, rate_actual %d, rate_requested %d\n",
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__func__, clock_divide, clock_rate, ssp_clk, ssp_sck, rate);
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}
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EXPORT_SYMBOL_GPL(mxs_ssp_set_clk_rate);
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