[ARM] 3992/1: i.MX/MX1 CPU Frequency scaling support

Support to change MX1 CPU frequency at runtime.
Tested on PiKRON's PiMX1 board and seems to be fully
stable up to 200 MHz end even as low as 8 MHz.

Signed-off-by: Pavel Pisa <[e-mail]>
Signed-off-by: Russell King <[e-mail]>

arch/arm/Kconfig

···
 
 endmenu
 
-if (ARCH_SA1100 || ARCH_INTEGRATOR || ARCH_OMAP)
+if (ARCH_SA1100 || ARCH_INTEGRATOR || ARCH_OMAP || ARCH_IMX )
 
 menu "CPU Frequency scaling"
 
···
 	  For details, take a look at <file:Documentation/cpu-freq>.
 
 	  If in doubt, say Y.
+
+config CPU_FREQ_IMX
+	tristate "CPUfreq driver for i.MX CPUs"
+	depends on ARCH_IMX && CPU_FREQ
+	default n
+	help
+	  This enables the CPUfreq driver for i.MX CPUs.
+
+	  If in doubt, say N.
 
 endmenu
 

arch/arm/mach-imx/Makefile

···
 
 obj-y			+= irq.o time.o dma.o generic.o
 
+obj-$(CONFIG_CPU_FREQ_IMX)	+= cpufreq.o
+
 # Specific board support
 obj-$(CONFIG_ARCH_MX1ADS) += mx1ads.o
 

arch/arm/mach-imx/cpufreq.c

···
+/*
+ * cpu.c: clock scaling for the iMX
+ *
+ * Copyright (C) 2000 2001, The Delft University of Technology
+ * Copyright (c) 2004 Sascha Hauer <[e-mail]>
+ * Copyright (C) 2006 Inky Lung <[e-mail]>
+ * Copyright (C) 2006 Pavel Pisa, PiKRON <[e-mail]>
+ *
+ * Based on SA1100 version written by:
+ * - Johan Pouwelse ([e-mail]): initial version
+ * - Erik Mouw ([e-mail]):
+ *
+ * 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
+ *
+ */
+
+/*#define DEBUG*/
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <asm/system.h>
+
+#include <asm/hardware.h>
+
+#include "generic.h"
+
+#ifndef __val2mfld
+#define __val2mfld(mask,val) (((mask)&~((mask)<<1))*(val)&(mask))
+#endif
+#ifndef __mfld2val
+#define __mfld2val(mask,val) (((val)&(mask))/((mask)&~((mask)<<1)))
+#endif
+
+#define CR_920T_CLOCK_MODE	0xC0000000
+#define CR_920T_FASTBUS_MODE	0x00000000
+#define CR_920T_ASYNC_MODE	0xC0000000
+
+static u32 mpctl0_at_boot;
+
+static void imx_set_async_mode(void)
+{
+	adjust_cr(CR_920T_CLOCK_MODE, CR_920T_ASYNC_MODE);
+}
+
+static void imx_set_fastbus_mode(void)
+{
+	adjust_cr(CR_920T_CLOCK_MODE, CR_920T_FASTBUS_MODE);
+}
+
+static void imx_set_mpctl0(u32 mpctl0)
+{
+	unsigned long flags;
+
+	if (mpctl0 == 0) {
+		local_irq_save(flags);
+		CSCR &= ~CSCR_MPEN;
+		local_irq_restore(flags);
+		return;
+	}
+
+	local_irq_save(flags);
+	MPCTL0 = mpctl0;
+	CSCR |= CSCR_MPEN;
+	local_irq_restore(flags);
+}
+
+/**
+ * imx_compute_mpctl - compute new PLL parameters
+ * @new_mpctl:	pointer to location assigned by new PLL control register value
+ * @cur_mpctl:	current PLL control register parameters
+ * @freq:	required frequency in Hz
+ * @relation:	is one of %CPUFREQ_RELATION_L (supremum)
+ *		and %CPUFREQ_RELATION_H (infimum)
+ */
+long imx_compute_mpctl(u32 *new_mpctl, u32 cur_mpctl, unsigned long freq, int relation)
+{
+        u32 f_ref = (CSCR & CSCR_SYSTEM_SEL) ? 16000000 : (CLK32 * 512);
+        u32 mfi;
+        u32 mfn;
+        u32 mfd;
+        u32 pd;
+	unsigned long long ll;
+	long l;
+	long quot;
+
+	/* Fdppl=2*Fref*(MFI+MFN/(MFD+1))/(PD+1) */
+	/*  PD=<0,15>, MFD=<1,1023>, MFI=<5,15> MFN=<0,1022> */
+
+	if (cur_mpctl) {
+		mfd = ((cur_mpctl >> 16) & 0x3ff) + 1;
+		pd =  ((cur_mpctl >> 26) & 0xf) + 1;
+	} else {
+		pd=2; mfd=313;
+	}
+
+	/* pd=2; mfd=313; mfi=8; mfn=183; */
+	/* (MFI+MFN/(MFD)) = Fdppl / (2*Fref) * (PD); */
+
+	quot = (f_ref + (1 << 9)) >> 10;
+	l = (freq * pd + quot) / (2 * quot);
+	mfi = l >> 10;
+	mfn = ((l & ((1 << 10) - 1)) * mfd + (1 << 9)) >> 10;
+
+	mfd -= 1;
+	pd -= 1;
+
+	*new_mpctl = ((mfi & 0xf) << 10) | (mfn & 0x3ff) | ((mfd & 0x3ff) << 16)
+		| ((pd & 0xf) << 26);
+
+	ll = 2 * (unsigned long long)f_ref * ( (mfi<<16) + (mfn<<16) / (mfd+1) );
+	quot = (pd+1) * (1<<16);
+	ll += quot / 2;
+	do_div(ll, quot);
+	freq = ll;
+
+	pr_debug(KERN_DEBUG "imx: new PLL parameters pd=%d mfd=%d mfi=%d mfn=%d, freq=%ld\n",
+		pd, mfd, mfi, mfn, freq);
+
+	return freq;
+}
+
+
+static int imx_verify_speed(struct cpufreq_policy *policy)
+{
+	if (policy->cpu != 0)
+		return -EINVAL;
+
+	cpufreq_verify_within_limits(policy, policy->cpuinfo.min_freq, policy->cpuinfo.max_freq);
+
+	return 0;
+}
+
+static unsigned int imx_get_speed(unsigned int cpu)
+{
+	unsigned int freq;
+	unsigned int cr;
+	unsigned int cscr;
+	unsigned int bclk_div;
+
+	if (cpu)
+		return 0;
+
+	cscr = CSCR;
+	bclk_div = __mfld2val(CSCR_BCLK_DIV, cscr) + 1;
+	cr = get_cr();
+
+	if((cr & CR_920T_CLOCK_MODE) == CR_920T_FASTBUS_MODE) {
+		freq = imx_get_system_clk();
+		freq = (freq + bclk_div/2) / bclk_div;
+	} else {
+		freq = imx_get_mcu_clk();
+		if (cscr & CSCR_MPU_PRESC)
+			freq /= 2;
+	}
+
+	freq = (freq + 500) / 1000;
+
+	return freq;
+}
+
+static int imx_set_target(struct cpufreq_policy *policy,
+			  unsigned int target_freq,
+			  unsigned int relation)
+{
+	struct cpufreq_freqs freqs;
+	u32 mpctl0 = 0;
+	u32 cscr;
+	unsigned long flags;
+	long freq;
+	long sysclk;
+	unsigned int bclk_div = 1;
+
+	freq = target_freq * 1000;
+
+	pr_debug(KERN_DEBUG "imx: requested frequency %ld Hz, mpctl0 at boot 0x%08x\n",
+			freq, mpctl0_at_boot);
+
+	sysclk = imx_get_system_clk();
+
+	if (freq > sysclk + 1000000) {
+		freq = imx_compute_mpctl(&mpctl0, mpctl0_at_boot, freq, relation);
+		if (freq < 0) {
+			printk(KERN_WARNING "imx: target frequency %ld Hz cannot be set\n", freq);
+			return -EINVAL;
+		}
+	} else {
+		if(freq + 1000 < sysclk) {
+			if (relation == CPUFREQ_RELATION_L)
+				bclk_div = (sysclk - 1000) / freq;
+			else
+				bclk_div = (sysclk + freq + 1000) / freq;
+
+			if(bclk_div > 16)
+				bclk_div = 16;
+		}
+		freq = (sysclk + bclk_div / 2) / bclk_div;
+	}
+
+	freqs.old = imx_get_speed(0);
+	freqs.new = (freq + 500) / 1000;
+	freqs.cpu = 0;
+	freqs.flags = 0;
+
+	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+	local_irq_save(flags);
+
+	imx_set_fastbus_mode();
+
+	imx_set_mpctl0(mpctl0);
+
+	cscr = CSCR;
+	cscr &= ~CSCR_BCLK_DIV;
+	cscr |= __val2mfld(CSCR_BCLK_DIV, bclk_div - 1);
+	CSCR = cscr;
+
+	if(mpctl0) {
+		CSCR |= CSCR_MPLL_RESTART;
+
+		/* Wait until MPLL is stablized */
+		while( CSCR & CSCR_MPLL_RESTART );
+
+		imx_set_async_mode();
+	}
+
+	local_irq_restore(flags);
+
+	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+	pr_debug(KERN_INFO "imx: set frequency %ld Hz, running from %s\n",
+			freq, mpctl0? "MPLL": "SPLL");
+
+	return 0;
+}
+
+static int __init imx_cpufreq_driver_init(struct cpufreq_policy *policy)
+{
+	printk(KERN_INFO "i.MX cpu freq change driver v1.0\n");
+
+	if (policy->cpu != 0)
+		return -EINVAL;
+
+	policy->cur = policy->min = policy->max = imx_get_speed(0);
+	policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
+	policy->cpuinfo.min_freq = 8000;
+	policy->cpuinfo.max_freq = 200000;
+	policy->cpuinfo.transition_latency = CPUFREQ_ETERNAL;
+	return 0;
+}
+
+static struct cpufreq_driver imx_driver = {
+	.flags		= CPUFREQ_STICKY,
+	.verify		= imx_verify_speed,
+	.target		= imx_set_target,
+	.get		= imx_get_speed,
+	.init		= imx_cpufreq_driver_init,
+	.name		= "imx",
+};
+
+static int __init imx_cpufreq_init(void)
+{
+
+	mpctl0_at_boot = 0;
+
+	if((CSCR & CSCR_MPEN) &&
+	   ((get_cr() & CR_920T_CLOCK_MODE) != CR_920T_FASTBUS_MODE))
+		mpctl0_at_boot = MPCTL0;
+
+	return cpufreq_register_driver(&imx_driver);
+}
+
+arch_initcall(imx_cpufreq_init);
+

include/asm-arm/arch-imx/imx-regs.h

···
 
 /* PLL registers */
 #define CSCR   __REG(IMX_PLL_BASE)        /* Clock Source Control Register */
-#define CSCR_SYSTEM_SEL (1<<16)
+#define CSCR_SPLL_RESTART	(1<<22)
+#define CSCR_MPLL_RESTART	(1<<21)
+#define CSCR_SYSTEM_SEL		(1<<16)
+#define CSCR_BCLK_DIV		(0xf<<10)
+#define CSCR_MPU_PRESC		(1<<15)
+#define CSCR_SPEN		(1<<1)
+#define CSCR_MPEN		(1<<0)
 
 #define MPCTL0 __REG(IMX_PLL_BASE + 0x4)  /* MCU PLL Control Register 0 */
 #define MPCTL1 __REG(IMX_PLL_BASE + 0x8)  /* MCU PLL and System Clock Register 1 */
 #define SPCTL0 __REG(IMX_PLL_BASE + 0xc)  /* System PLL Control Register 0 */
 #define SPCTL1 __REG(IMX_PLL_BASE + 0x10) /* System PLL Control Register 1 */
 #define PCDR   __REG(IMX_PLL_BASE + 0x20) /* Peripheral Clock Divider Register */
-
-#define CSCR_MPLL_RESTART (1<<21)
 
 /*
  *  GPIO Module and I/O Multiplexer