src/kernel/linux/v4.19/drivers/clk/mxs/clk-ssp.c

/*
 * Copyright 2012 DENX Software Engineering, GmbH
 *
 * Pulled from code:
 * Portions copyright (C) 2003 Russell King, PXA MMCI Driver
 * Portions copyright (C) 2004-2005 Pierre Ossman, W83L51xD SD/MMC driver
 *
 * Copyright 2008 Embedded Alley Solutions, Inc.
 * Copyright 2009-2011 Freescale Semiconductor, Inc.
 *
 * The code contained herein is licensed under the GNU General Public
 * License. You may obtain a copy of the GNU General Public License
 * Version 2 or later at the following locations:
 *
 * http://www.opensource.org/licenses/gpl-license.html
 * http://www.gnu.org/copyleft/gpl.html
 */

#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/clk.h>
#include <linux/module.h>
#include <linux/device.h>
#include <linux/io.h>
#include <linux/spi/mxs-spi.h>

void mxs_ssp_set_clk_rate(struct mxs_ssp *ssp, unsigned int rate)
{
	unsigned int ssp_clk, ssp_sck;
	u32 clock_divide, clock_rate;
	u32 val;

	ssp_clk = clk_get_rate(ssp->clk);

	for (clock_divide = 2; clock_divide <= 254; clock_divide += 2) {
		clock_rate = DIV_ROUND_UP(ssp_clk, rate * clock_divide);
		clock_rate = (clock_rate > 0) ? clock_rate - 1 : 0;
		if (clock_rate <= 255)
			break;
	}

	if (clock_divide > 254) {
		dev_err(ssp->dev,
			"%s: cannot set clock to %d\n", __func__, rate);
		return;
	}

	ssp_sck = ssp_clk / clock_divide / (1 + clock_rate);

	val = readl(ssp->base + HW_SSP_TIMING(ssp));
	val &= ~(BM_SSP_TIMING_CLOCK_DIVIDE | BM_SSP_TIMING_CLOCK_RATE);
	val |= BF_SSP(clock_divide, TIMING_CLOCK_DIVIDE);
	val |= BF_SSP(clock_rate, TIMING_CLOCK_RATE);
	writel(val, ssp->base + HW_SSP_TIMING(ssp));

	ssp->clk_rate = ssp_sck;

	dev_dbg(ssp->dev,
		"%s: clock_divide %d, clock_rate %d, ssp_clk %d, rate_actual %d, rate_requested %d\n",
		__func__, clock_divide, clock_rate, ssp_clk, ssp_sck, rate);
}
EXPORT_SYMBOL_GPL(mxs_ssp_set_clk_rate);