arch/arm/cpu/arm926ejs/mxs/clock.c - uboot/armada - Git at Google

 /*
  * Freescale i.MX28 clock setup code
  *
  * Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
  * on behalf of DENX Software Engineering GmbH
  *
  * Based on code from LTIB:
  * Copyright (C) 2010 Freescale Semiconductor, Inc.
  *
  * See file CREDITS for list of people who contributed to this
  * project.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation; either version 2 of
  * the License, or (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
  * MA 02111-1307 USA
  */

 #include <common.h>
 #include <asm/errno.h>
 #include <asm/io.h>
 #include <asm/arch/clock.h>
 #include <asm/arch/imx-regs.h>

 /* The PLL frequency is always 480MHz, see section 10.2 in iMX28 datasheet. */
 #define	PLL_FREQ_KHZ	480000
 #define	PLL_FREQ_COEF	18
 /* The XTAL frequency is always 24MHz, see section 10.2 in iMX28 datasheet. */
 #define	XTAL_FREQ_KHZ	24000

 #define	PLL_FREQ_MHZ	(PLL_FREQ_KHZ / 1000)
 #define	XTAL_FREQ_MHZ	(XTAL_FREQ_KHZ / 1000)

 static uint32_t mx28_get_pclk(void)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

 	uint32_t clkctrl, clkseq, div;
 	uint8_t clkfrac, frac;

 	clkctrl = readl(&clkctrl_regs->hw_clkctrl_cpu);

 	/* No support of fractional divider calculation */
 	if (clkctrl &
 		(CLKCTRL_CPU_DIV_XTAL_FRAC_EN | CLKCTRL_CPU_DIV_CPU_FRAC_EN)) {
 		return 0;
 	}

 	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);

 	/* XTAL Path */
 	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_CPU) {
 		div = (clkctrl & CLKCTRL_CPU_DIV_XTAL_MASK) >>
 			CLKCTRL_CPU_DIV_XTAL_OFFSET;
 		return XTAL_FREQ_MHZ / div;
 	}

 	/* REF Path */
 	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac0[CLKCTRL_FRAC0_CPU]);
 	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
 	div = clkctrl & CLKCTRL_CPU_DIV_CPU_MASK;
 	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
 }

 static uint32_t mx28_get_hclk(void)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

 	uint32_t div;
 	uint32_t clkctrl;

 	clkctrl = readl(&clkctrl_regs->hw_clkctrl_hbus);

 	/* No support of fractional divider calculation */
 	if (clkctrl & CLKCTRL_HBUS_DIV_FRAC_EN)
 		return 0;

 	div = clkctrl & CLKCTRL_HBUS_DIV_MASK;
 	return mx28_get_pclk() / div;
 }

 static uint32_t mx28_get_emiclk(void)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

 	uint32_t clkctrl, clkseq, div;
 	uint8_t clkfrac, frac;

 	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);
 	clkctrl = readl(&clkctrl_regs->hw_clkctrl_emi);

 	/* XTAL Path */
 	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_EMI) {
 		div = (clkctrl & CLKCTRL_EMI_DIV_XTAL_MASK) >>
 			CLKCTRL_EMI_DIV_XTAL_OFFSET;
 		return XTAL_FREQ_MHZ / div;
 	}

 	/* REF Path */
 	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac0[CLKCTRL_FRAC0_EMI]);
 	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
 	div = clkctrl & CLKCTRL_EMI_DIV_EMI_MASK;
 	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
 }

 static uint32_t mx28_get_gpmiclk(void)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

 	uint32_t clkctrl, clkseq, div;
 	uint8_t clkfrac, frac;

 	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);
 	clkctrl = readl(&clkctrl_regs->hw_clkctrl_gpmi);

 	/* XTAL Path */
 	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_GPMI) {
 		div = clkctrl & CLKCTRL_GPMI_DIV_MASK;
 		return XTAL_FREQ_MHZ / div;
 	}

 	/* REF Path */
 	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac1[CLKCTRL_FRAC1_GPMI]);
 	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
 	div = clkctrl & CLKCTRL_GPMI_DIV_MASK;
 	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
 }

 /*
  * Set IO clock frequency, in kHz
  */
 void mx28_set_ioclk(enum mxs_ioclock io, uint32_t freq)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
 	uint32_t div;
 	int io_reg;

 	if (freq == 0)
 		return;

 	if ((io < MXC_IOCLK0) || (io > MXC_IOCLK1))
 		return;

 	div = (PLL_FREQ_KHZ * PLL_FREQ_COEF) / freq;

 	if (div < 18)
 		div = 18;

 	if (div > 35)
 		div = 35;

 	io_reg = CLKCTRL_FRAC0_IO0 - io;	/* Register order is reversed */
 	writeb(CLKCTRL_FRAC_CLKGATE,
 		&clkctrl_regs->hw_clkctrl_frac0_set[io_reg]);
 	writeb(CLKCTRL_FRAC_CLKGATE | (div & CLKCTRL_FRAC_FRAC_MASK),
 		&clkctrl_regs->hw_clkctrl_frac0[io_reg]);
 	writeb(CLKCTRL_FRAC_CLKGATE,
 		&clkctrl_regs->hw_clkctrl_frac0_clr[io_reg]);
 }

 /*
  * Get IO clock, returns IO clock in kHz
  */
 static uint32_t mx28_get_ioclk(enum mxs_ioclock io)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
 	uint8_t ret;
 	int io_reg;

 	if ((io < MXC_IOCLK0) || (io > MXC_IOCLK1))
 		return 0;

 	io_reg = CLKCTRL_FRAC0_IO0 - io;	/* Register order is reversed */

 	ret = readb(&clkctrl_regs->hw_clkctrl_frac0[io_reg]) &
 		CLKCTRL_FRAC_FRAC_MASK;

 	return (PLL_FREQ_KHZ * PLL_FREQ_COEF) / ret;
 }

 /*
  * Configure SSP clock frequency, in kHz
  */
 void mx28_set_sspclk(enum mxs_sspclock ssp, uint32_t freq, int xtal)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
 	uint32_t clk, clkreg;

 	if (ssp > MXC_SSPCLK3)
 		return;

 	clkreg = (uint32_t)(&clkctrl_regs->hw_clkctrl_ssp0) +
 			(ssp * sizeof(struct mxs_register_32));

 	clrbits_le32(clkreg, CLKCTRL_SSP_CLKGATE);
 	while (readl(clkreg) & CLKCTRL_SSP_CLKGATE)
 		;

 	if (xtal)
 		clk = XTAL_FREQ_KHZ;
 	else
 		clk = mx28_get_ioclk(ssp >> 1);

 	if (freq > clk)
 		return;

 	/* Calculate the divider and cap it if necessary */
 	clk /= freq;
 	if (clk > CLKCTRL_SSP_DIV_MASK)
 		clk = CLKCTRL_SSP_DIV_MASK;

 	clrsetbits_le32(clkreg, CLKCTRL_SSP_DIV_MASK, clk);
 	while (readl(clkreg) & CLKCTRL_SSP_BUSY)
 		;

 	if (xtal)
 		writel(CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp,
 			&clkctrl_regs->hw_clkctrl_clkseq_set);
 	else
 		writel(CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp,
 			&clkctrl_regs->hw_clkctrl_clkseq_clr);
 }

 /*
  * Return SSP frequency, in kHz
  */
 static uint32_t mx28_get_sspclk(enum mxs_sspclock ssp)
 {
 	struct mxs_clkctrl_regs *clkctrl_regs =
 		(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
 	uint32_t clkreg;
 	uint32_t clk, tmp;

 	if (ssp > MXC_SSPCLK3)
 		return 0;

 	tmp = readl(&clkctrl_regs->hw_clkctrl_clkseq);
 	if (tmp & (CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp))
 		return XTAL_FREQ_KHZ;

 	clkreg = (uint32_t)(&clkctrl_regs->hw_clkctrl_ssp0) +
 			(ssp * sizeof(struct mxs_register_32));

 	tmp = readl(clkreg) & CLKCTRL_SSP_DIV_MASK;

 	if (tmp == 0)
 		return 0;

 	clk = mx28_get_ioclk(ssp >> 1);

 	return clk / tmp;
 }

 /*
  * Set SSP/MMC bus frequency, in kHz)
  */
 void mx28_set_ssp_busclock(unsigned int bus, uint32_t freq)
 {
 	struct mxs_ssp_regs *ssp_regs;
 	const uint32_t sspclk = mx28_get_sspclk(bus);
 	uint32_t reg;
 	uint32_t divide, rate, tgtclk;

 	ssp_regs = (struct mxs_ssp_regs *)(MXS_SSP0_BASE + (bus * 0x2000));

 	/*
 	 * SSP bit rate = SSPCLK / (CLOCK_DIVIDE * (1 + CLOCK_RATE)),
 	 * CLOCK_DIVIDE has to be an even value from 2 to 254, and
 	 * CLOCK_RATE could be any integer from 0 to 255.
 	 */
 	for (divide = 2; divide < 254; divide += 2) {
 		rate = sspclk / freq / divide;
 		if (rate <= 256)
 			break;
 	}

 	tgtclk = sspclk / divide / rate;
 	while (tgtclk > freq) {
 		rate++;
 		tgtclk = sspclk / divide / rate;
 	}
 	if (rate > 256)
 		rate = 256;

 	/* Always set timeout the maximum */
 	reg = SSP_TIMING_TIMEOUT_MASK |
 		(divide << SSP_TIMING_CLOCK_DIVIDE_OFFSET) |
 		((rate - 1) << SSP_TIMING_CLOCK_RATE_OFFSET);
 	writel(reg, &ssp_regs->hw_ssp_timing);

 	debug("SPI%d: Set freq rate to %d KHz (requested %d KHz)\n",
 		bus, tgtclk, freq);
 }

 uint32_t mxc_get_clock(enum mxc_clock clk)
 {
 	switch (clk) {
 	case MXC_ARM_CLK:
 		return mx28_get_pclk() * 1000000;
 	case MXC_GPMI_CLK:
 		return mx28_get_gpmiclk() * 1000000;
 	case MXC_AHB_CLK:
 	case MXC_IPG_CLK:
 		return mx28_get_hclk() * 1000000;
 	case MXC_EMI_CLK:
 		return mx28_get_emiclk();
 	case MXC_IO0_CLK:
 		return mx28_get_ioclk(MXC_IOCLK0);
 	case MXC_IO1_CLK:
 		return mx28_get_ioclk(MXC_IOCLK1);
 	case MXC_SSP0_CLK:
 		return mx28_get_sspclk(MXC_SSPCLK0);
 	case MXC_SSP1_CLK:
 		return mx28_get_sspclk(MXC_SSPCLK1);
 	case MXC_SSP2_CLK:
 		return mx28_get_sspclk(MXC_SSPCLK2);
 	case MXC_SSP3_CLK:
 		return mx28_get_sspclk(MXC_SSPCLK3);
 	case MXC_XTAL_CLK:
 		return XTAL_FREQ_KHZ * 1000;
 	}

 	return 0;
 }
	/*
	* Freescale i.MX28 clock setup code
	*
	* Copyright (C) 2011 Marek Vasut <marek.vasut@gmail.com>
	* on behalf of DENX Software Engineering GmbH
	*
	* Based on code from LTIB:
	* Copyright (C) 2010 Freescale Semiconductor, Inc.
	*
	* See file CREDITS for list of people who contributed to this
	* project.
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation; either version 2 of
	* the License, or (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston,
	* MA 02111-1307 USA
	*/

	#include <common.h>
	#include <asm/errno.h>
	#include <asm/io.h>
	#include <asm/arch/clock.h>
	#include <asm/arch/imx-regs.h>

	/* The PLL frequency is always 480MHz, see section 10.2 in iMX28 datasheet. */
	#define PLL_FREQ_KHZ 480000
	#define PLL_FREQ_COEF 18
	/* The XTAL frequency is always 24MHz, see section 10.2 in iMX28 datasheet. */
	#define XTAL_FREQ_KHZ 24000

	#define PLL_FREQ_MHZ (PLL_FREQ_KHZ / 1000)
	#define XTAL_FREQ_MHZ (XTAL_FREQ_KHZ / 1000)

	static uint32_t mx28_get_pclk(void)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

	uint32_t clkctrl, clkseq, div;
	uint8_t clkfrac, frac;

	clkctrl = readl(&clkctrl_regs->hw_clkctrl_cpu);

	/* No support of fractional divider calculation */
	if (clkctrl &
	(CLKCTRL_CPU_DIV_XTAL_FRAC_EN \| CLKCTRL_CPU_DIV_CPU_FRAC_EN)) {
	return 0;
	}

	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);

	/* XTAL Path */
	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_CPU) {
	div = (clkctrl & CLKCTRL_CPU_DIV_XTAL_MASK) >>
	CLKCTRL_CPU_DIV_XTAL_OFFSET;
	return XTAL_FREQ_MHZ / div;
	}

	/* REF Path */
	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac0[CLKCTRL_FRAC0_CPU]);
	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
	div = clkctrl & CLKCTRL_CPU_DIV_CPU_MASK;
	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
	}

	static uint32_t mx28_get_hclk(void)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

	uint32_t div;
	uint32_t clkctrl;

	clkctrl = readl(&clkctrl_regs->hw_clkctrl_hbus);

	/* No support of fractional divider calculation */
	if (clkctrl & CLKCTRL_HBUS_DIV_FRAC_EN)
	return 0;

	div = clkctrl & CLKCTRL_HBUS_DIV_MASK;
	return mx28_get_pclk() / div;
	}

	static uint32_t mx28_get_emiclk(void)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

	uint32_t clkctrl, clkseq, div;
	uint8_t clkfrac, frac;

	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);
	clkctrl = readl(&clkctrl_regs->hw_clkctrl_emi);

	/* XTAL Path */
	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_EMI) {
	div = (clkctrl & CLKCTRL_EMI_DIV_XTAL_MASK) >>
	CLKCTRL_EMI_DIV_XTAL_OFFSET;
	return XTAL_FREQ_MHZ / div;
	}

	/* REF Path */
	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac0[CLKCTRL_FRAC0_EMI]);
	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
	div = clkctrl & CLKCTRL_EMI_DIV_EMI_MASK;
	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
	}

	static uint32_t mx28_get_gpmiclk(void)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;

	uint32_t clkctrl, clkseq, div;
	uint8_t clkfrac, frac;

	clkseq = readl(&clkctrl_regs->hw_clkctrl_clkseq);
	clkctrl = readl(&clkctrl_regs->hw_clkctrl_gpmi);

	/* XTAL Path */
	if (clkseq & CLKCTRL_CLKSEQ_BYPASS_GPMI) {
	div = clkctrl & CLKCTRL_GPMI_DIV_MASK;
	return XTAL_FREQ_MHZ / div;
	}

	/* REF Path */
	clkfrac = readb(&clkctrl_regs->hw_clkctrl_frac1[CLKCTRL_FRAC1_GPMI]);
	frac = clkfrac & CLKCTRL_FRAC_FRAC_MASK;
	div = clkctrl & CLKCTRL_GPMI_DIV_MASK;
	return (PLL_FREQ_MHZ * PLL_FREQ_COEF / frac) / div;
	}

	/*
	* Set IO clock frequency, in kHz
	*/
	void mx28_set_ioclk(enum mxs_ioclock io, uint32_t freq)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
	uint32_t div;
	int io_reg;

	if (freq == 0)
	return;

	if ((io < MXC_IOCLK0) \|\| (io > MXC_IOCLK1))
	return;

	div = (PLL_FREQ_KHZ * PLL_FREQ_COEF) / freq;

	if (div < 18)
	div = 18;

	if (div > 35)
	div = 35;

	io_reg = CLKCTRL_FRAC0_IO0 - io; /* Register order is reversed */
	writeb(CLKCTRL_FRAC_CLKGATE,
	&clkctrl_regs->hw_clkctrl_frac0_set[io_reg]);
	writeb(CLKCTRL_FRAC_CLKGATE \| (div & CLKCTRL_FRAC_FRAC_MASK),
	&clkctrl_regs->hw_clkctrl_frac0[io_reg]);
	writeb(CLKCTRL_FRAC_CLKGATE,
	&clkctrl_regs->hw_clkctrl_frac0_clr[io_reg]);
	}

	/*
	* Get IO clock, returns IO clock in kHz
	*/
	static uint32_t mx28_get_ioclk(enum mxs_ioclock io)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
	uint8_t ret;
	int io_reg;

	if ((io < MXC_IOCLK0) \|\| (io > MXC_IOCLK1))
	return 0;

	io_reg = CLKCTRL_FRAC0_IO0 - io; /* Register order is reversed */

	ret = readb(&clkctrl_regs->hw_clkctrl_frac0[io_reg]) &
	CLKCTRL_FRAC_FRAC_MASK;

	return (PLL_FREQ_KHZ * PLL_FREQ_COEF) / ret;
	}

	/*
	* Configure SSP clock frequency, in kHz
	*/
	void mx28_set_sspclk(enum mxs_sspclock ssp, uint32_t freq, int xtal)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
	uint32_t clk, clkreg;

	if (ssp > MXC_SSPCLK3)
	return;

	clkreg = (uint32_t)(&clkctrl_regs->hw_clkctrl_ssp0) +
	(ssp * sizeof(struct mxs_register_32));

	clrbits_le32(clkreg, CLKCTRL_SSP_CLKGATE);
	while (readl(clkreg) & CLKCTRL_SSP_CLKGATE)
	;

	if (xtal)
	clk = XTAL_FREQ_KHZ;
	else
	clk = mx28_get_ioclk(ssp >> 1);

	if (freq > clk)
	return;

	/* Calculate the divider and cap it if necessary */
	clk /= freq;
	if (clk > CLKCTRL_SSP_DIV_MASK)
	clk = CLKCTRL_SSP_DIV_MASK;

	clrsetbits_le32(clkreg, CLKCTRL_SSP_DIV_MASK, clk);
	while (readl(clkreg) & CLKCTRL_SSP_BUSY)
	;

	if (xtal)
	writel(CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp,
	&clkctrl_regs->hw_clkctrl_clkseq_set);
	else
	writel(CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp,
	&clkctrl_regs->hw_clkctrl_clkseq_clr);
	}

	/*
	* Return SSP frequency, in kHz
	*/
	static uint32_t mx28_get_sspclk(enum mxs_sspclock ssp)
	{
	struct mxs_clkctrl_regs *clkctrl_regs =
	(struct mxs_clkctrl_regs *)MXS_CLKCTRL_BASE;
	uint32_t clkreg;
	uint32_t clk, tmp;

	if (ssp > MXC_SSPCLK3)
	return 0;

	tmp = readl(&clkctrl_regs->hw_clkctrl_clkseq);
	if (tmp & (CLKCTRL_CLKSEQ_BYPASS_SSP0 << ssp))
	return XTAL_FREQ_KHZ;

	clkreg = (uint32_t)(&clkctrl_regs->hw_clkctrl_ssp0) +
	(ssp * sizeof(struct mxs_register_32));

	tmp = readl(clkreg) & CLKCTRL_SSP_DIV_MASK;

	if (tmp == 0)
	return 0;

	clk = mx28_get_ioclk(ssp >> 1);

	return clk / tmp;
	}

	/*
	* Set SSP/MMC bus frequency, in kHz)
	*/
	void mx28_set_ssp_busclock(unsigned int bus, uint32_t freq)
	{
	struct mxs_ssp_regs *ssp_regs;
	const uint32_t sspclk = mx28_get_sspclk(bus);
	uint32_t reg;
	uint32_t divide, rate, tgtclk;

	ssp_regs = (struct mxs_ssp_regs )(MXS_SSP0_BASE + (bus 0x2000));

	/*
	* SSP bit rate = SSPCLK / (CLOCK_DIVIDE * (1 + CLOCK_RATE)),
	* CLOCK_DIVIDE has to be an even value from 2 to 254, and
	* CLOCK_RATE could be any integer from 0 to 255.
	*/
	for (divide = 2; divide < 254; divide += 2) {
	rate = sspclk / freq / divide;
	if (rate <= 256)
	break;
	}

	tgtclk = sspclk / divide / rate;
	while (tgtclk > freq) {
	rate++;
	tgtclk = sspclk / divide / rate;
	}
	if (rate > 256)
	rate = 256;

	/* Always set timeout the maximum */
	reg = SSP_TIMING_TIMEOUT_MASK \|
	(divide << SSP_TIMING_CLOCK_DIVIDE_OFFSET) \|
	((rate - 1) << SSP_TIMING_CLOCK_RATE_OFFSET);
	writel(reg, &ssp_regs->hw_ssp_timing);

	debug("SPI%d: Set freq rate to %d KHz (requested %d KHz)\n",
	bus, tgtclk, freq);
	}

	uint32_t mxc_get_clock(enum mxc_clock clk)
	{
	switch (clk) {
	case MXC_ARM_CLK:
	return mx28_get_pclk() * 1000000;
	case MXC_GPMI_CLK:
	return mx28_get_gpmiclk() * 1000000;
	case MXC_AHB_CLK:
	case MXC_IPG_CLK:
	return mx28_get_hclk() * 1000000;
	case MXC_EMI_CLK:
	return mx28_get_emiclk();
	case MXC_IO0_CLK:
	return mx28_get_ioclk(MXC_IOCLK0);
	case MXC_IO1_CLK:
	return mx28_get_ioclk(MXC_IOCLK1);
	case MXC_SSP0_CLK:
	return mx28_get_sspclk(MXC_SSPCLK0);
	case MXC_SSP1_CLK:
	return mx28_get_sspclk(MXC_SSPCLK1);
	case MXC_SSP2_CLK:
	return mx28_get_sspclk(MXC_SSPCLK2);
	case MXC_SSP3_CLK:
	return mx28_get_sspclk(MXC_SSPCLK3);
	case MXC_XTAL_CLK:
	return XTAL_FREQ_KHZ * 1000;
	}

	return 0;
	}