[PATCH] cpufreq driver for the PXA255 processor.

[Ian Campbell <icampbell@arcom.com>]

Hi Dave,

Below is a patch adding cpufreq support for the PXA255 Xscale processor.
The driver was originally from Intrinsyc Software and spent some time in
the old -bkpxa tree. Since then I've tweaked it a little and have been
using it successfully for some time.

It was reviewed by several people on the list some time ago and I think
it is ready to go in, I missed the boat for 2.6.14 due to the list being
down, but I figure since 2.6.14 is due any day now it would be a good
time to start sending stuff in preparation for 2.6.15 opening up.

Signed-off-by: Ian Campbell <icampbell@arcom.com>

Index: 2.6/arch/arm/Kconfig
===================================================================
--- 2.6.orig/arch/arm/Kconfig	2005-08-24 15:04:57.000000000 +0100
+++ 2.6/arch/arm/Kconfig	2005-08-26 11:26:06.000000000 +0100
@@ -516,7 +516,7 @@
 
 endmenu
 
-if (ARCH_SA1100 || ARCH_INTEGRATOR || ARCH_OMAP1)
+if (ARCH_SA1100 || ARCH_INTEGRATOR || ARCH_OMAP1 || ARCH_PXA)
 
 menu "CPU Frequency scaling"
 
@@ -543,6 +543,12 @@
 
 	  If in doubt, say Y.
 
+config CPU_FREQ_PXA25x
+	bool
+	select CPU_FREQ_TABLE
+	depends on CPU_FREQ && PXA25x
+	default y
+
 endmenu
 
 endif
Index: 2.6/arch/arm/mach-pxa/Makefile
===================================================================
--- 2.6.orig/arch/arm/mach-pxa/Makefile	2005-08-24 15:04:58.000000000 +0100
+++ 2.6/arch/arm/mach-pxa/Makefile	2005-08-26 11:26:06.000000000 +0100
@@ -22,6 +22,9 @@
 
 obj-$(CONFIG_LEDS) += $(led-y)
 
+# CPU freq support
+obj-$(CONFIG_CPU_FREQ_PXA25x) += cpu-pxa25x.o
+
 # Misc features
 obj-$(CONFIG_PM) += pm.o sleep.o
 
Index: 2.6/Documentation/cpu-freq/user-guide.txt
===================================================================
--- 2.6.orig/Documentation/cpu-freq/user-guide.txt	2005-05-27 06:06:46.000000000 +0100
+++ 2.6/Documentation/cpu-freq/user-guide.txt	2005-08-26 11:26:06.000000000 +0100
@@ -45,6 +45,7 @@
 ARM Integrator
 ARM-SA1100
 ARM-SA1110
+Intel XScale PXA25x
 
 
 1.2 x86
Index: 2.6/arch/arm/mach-pxa/cpu-pxa25x.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ 2.6/arch/arm/mach-pxa/cpu-pxa25x.c	2005-08-26 11:26:09.000000000 +0100
@@ -0,0 +1,342 @@
+/*
+ *  linux/arch/arm/mach-pxa/cpu-pxa.c
+ *
+ *  Copyright (C) 2002,2003 Intrinsyc Software
+ *
+ * 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
+ *
+ * History:
+ *   31-Jul-2002 : Initial version [FB]
+ *   29-Jan-2003 : added PXA255 support [FB]
+ *   20-Apr-2003 : ported to v2.5 (Dustin McIntire, Sensoria Corp.)
+ *   18-Jul-2005 : updated for latest kernel (2.6.13-rc), cleanup for submission
+ *                 (Ian Campbell, Arcom Control Systems)
+ *
+ * Note:
+ *   This driver may change the memory bus clock rate, but will not do any
+ *   platform specific access timing changes... for example if you have flash
+ *   memory connected to CS0, you will need to register a platform specific
+ *   notifier which will adjust the memory access strobes to maintain a
+ *   minimum strobe width.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+#include <linux/init.h>
+#include <linux/cpufreq.h>
+#include <linux/moduleparam.h>
+
+#include <asm/hardware.h>
+
+#include <asm/arch/pxa-regs.h>
+
+#define dprintk(msg...) cpufreq_debug_printk(CPUFREQ_DEBUG_DRIVER, "pxa25x", msg)
+
+struct pxa_freq {
+	unsigned int khz;
+	unsigned int membus;
+	unsigned int cccr;
+	unsigned int div2;
+};
+
+/* Define the refresh period in mSec for the SDRAM and the number of rows */
+#define SDRAM_TREF          64		/* standard 64ms SDRAM */
+#define SDRAM_ROWS          8192	/* 64MB=8192 32MB=4096 */
+#define MDREFR_DRI(x)       ((x*SDRAM_TREF)/(SDRAM_ROWS*32))
+
+#define CCLKCFG_TURBO       0x1
+#define CCLKCFG_FCS         0x2
+#define PXA25x_MIN_FREQ     99532
+#define PXA25x_MAX_FREQ     398131
+#define MDREFR_DB2_MASK     (MDREFR_K2DB2 | MDREFR_K1DB2)
+#define MDREFR_DRI_MASK     0xFFF
+
+/* Use the run mode frequencies for performance */
+static struct pxa_freq pxa25x_performance_freqs[] = {
+	/* CPU   MEMBUS  CCCR   DIV2 */
+	{99532,   99532, 0x121, 1},	/* run= 99, turbo= 99, PXbus=50,  SDRAM=50 */
+	{132710, 132710, 0x123, 1},	/* run=133, turbo=133, PXbus=66,  SDRAM=66 */
+	{199065,  99532, 0x141, 0},	/* run=199, turbo=199, PXbus=99,  SDRAM=99 */
+	{265421, 132710, 0x143, 1},	/* run=265, turbo=265, PXbus=133, SDRAM=66 */
+	{331776, 165888, 0x145, 1},	/* run=331, turbo=331, PXbus=166, SDRAM=83 */
+	{398131,  99532, 0x161, 0},	/* run=398, turbo=398, PXbus=196, SDRAM=99 */
+};
+
+static struct cpufreq_frequency_table pxa25x_performance_freq_table[ARRAY_SIZE(pxa25x_performance_freqs)+1];
+
+/* Use the turbo mode frequencies for powersave */
+static struct pxa_freq pxa25x_powersave_freqs[] = {
+	/* CPU   MEMBUS CCCR   DIV2 */
+	{99532,  99532, 0x121, 1},	/* run=99,  turbo= 99, PXbus=50, SDRAM=50 */
+	{199065, 99532, 0x221, 0},	/* run=99,  turbo=199, PXbus=50, SDRAM=99 */
+	{298598, 99532, 0x321, 0},	/* run=99,  turbo=287, PXbus=50, SDRAM=99 */
+	{398131, 99532, 0x241, 0},	/* run=199, turbo=398, PXbus=99, SDRAM=99 */
+};
+
+static struct cpufreq_frequency_table pxa25x_powersave_freq_table[ARRAY_SIZE(pxa25x_powersave_freqs)+1];
+
+/* currently selected frequency table */
+struct pxa_freq *pxa_freq_settings;
+struct cpufreq_frequency_table *pxa_freq_table;
+
+extern unsigned get_clk_frequency_khz(int info);
+
+static unsigned int max_frequency = PXA25x_MAX_FREQ;
+static int performance = 1;
+
+/*
+ * This option can be used if you have one of the 200MHz PXA25x parts by adding
+ * cpu_pxa25x.max_frequency=199065 to the kernel command line
+ */
+module_param(max_frequency, int, 0);
+MODULE_PARM_DESC(max_frequency, "Set the maximum cpu frequency");
+
+module_param(performance, int, 0);
+MODULE_PARM_DESC(performance, "Use 1=performance instead of powersave frequency tables");
+
+static void pxa_select_freq_table(struct cpufreq_policy *policy)
+{
+	cpufreq_frequency_table_put_attr(policy->cpu);
+
+	if (performance) {
+		dprintk("selecting performance tables\n");
+		pxa_freq_settings = pxa25x_performance_freqs;
+		pxa_freq_table = pxa25x_performance_freq_table;
+	} else {
+		dprintk("selecting powersave tables\n");
+		pxa_freq_settings = pxa25x_powersave_freqs;
+		pxa_freq_table = pxa25x_powersave_freq_table;
+	}
+
+	cpufreq_frequency_table_get_attr(pxa_freq_table, policy->cpu);		
+}
+
+/* find a valid frequency point */
+static int pxa_verify_policy(struct cpufreq_policy *policy)
+{
+	int ret;
+
+	pxa_select_freq_table(policy);
+
+	ret = cpufreq_frequency_table_verify(policy, pxa_freq_table);
+
+	dprintk("verified CPU policy: %dKhz min to %dKhz max\n",
+		policy->min, policy->max);
+
+	return ret;
+}
+
+static int pxa_set_target(struct cpufreq_policy *policy,
+			  unsigned int target_freq, unsigned int relation)
+{
+	int idx;
+	struct cpufreq_freqs freqs;
+	unsigned long flags;
+	unsigned int unused;
+	unsigned int preset_mdrefr, postset_mdrefr;
+	void *ramstart;
+
+	/* Lookup the next frequency */
+	if (cpufreq_frequency_table_target(policy, pxa_freq_table,
+					   target_freq, relation, &idx))
+		return -EINVAL;
+
+	freqs.old = get_clk_frequency_khz(0);
+	freqs.new = pxa_freq_settings[idx].khz;
+	freqs.cpu = policy->cpu;
+
+	if (freqs.new == freqs.old && pxa_freq_settings[idx].cccr == CCCR)
+		return 0;
+
+	dprintk("changing CPU frequency to %d.%03d Mhz (SDRAM %d Mhz, CCCR %#04x)\n",
+		freqs.new / 1000, freqs.new % 1000,
+		(pxa_freq_settings[idx].div2) ?
+		(pxa_freq_settings[idx].membus / 2000) :
+		(pxa_freq_settings[idx].membus / 1000),
+		pxa_freq_settings[idx].cccr);
+
+	ramstart = phys_to_virt(0xa0000000);
+
+	/*
+	 * Tell everyone what we're about to do...
+	 * you should add a notify client with any platform specific
+	 * Vcc changing capability
+	 */
+	cpufreq_notify_transition(&freqs, CPUFREQ_PRECHANGE);
+
+	/* Calculate the next MDREFR.  If we're slowing down the SDRAM clock
+	 * we need to preset the smaller DRI before the change.  If we're speeding
+	 * up we need to set the larger DRI value after the change.
+	 */
+	preset_mdrefr = postset_mdrefr = MDREFR;
+	if ((MDREFR & MDREFR_DRI_MASK) > MDREFR_DRI(pxa_freq_settings[idx].membus)) {
+		preset_mdrefr = (preset_mdrefr & ~MDREFR_DRI_MASK) |
+			MDREFR_DRI(pxa_freq_settings[idx].membus);
+	}
+	postset_mdrefr = (postset_mdrefr & ~MDREFR_DRI_MASK) |
+		MDREFR_DRI(pxa_freq_settings[idx].membus);
+
+	/* If we're dividing the memory clock by two for the SDRAM clock, this
+	 * must be set prior to the change.  Clearing the divide must be done
+	 * after the change.
+	 */
+	if (pxa_freq_settings[idx].div2) {
+		preset_mdrefr |= MDREFR_DB2_MASK;
+		postset_mdrefr |= MDREFR_DB2_MASK;
+	} else {
+		postset_mdrefr &= ~MDREFR_DB2_MASK;
+	}
+
+	local_irq_save(flags);
+
+	/* Set new the CCCR */
+	CCCR = pxa_freq_settings[idx].cccr;
+
+	__asm__ __volatile__("                              \
+        ldr r4, [%1] ;          /* load MDREFR */           \
+        b   2f ;                                            \
+        .align  5 ;                                         \
+1:                                                          \
+        str %4, [%1] ;          /* preset the MDREFR */     \
+        mcr p14, 0, %2, c6, c0, 0 ; /* set CCLKCFG[FCS] */  \
+        str %5, [%1] ;          /* postset the MDREFR */    \
+                                                            \
+        b   3f       ;                                      \
+2:      b   1b       ;                                      \
+3:      nop          ;                                      \
+        "
+	: "=&r"(unused)
+	: "r"(&MDREFR), "r"(CCLKCFG_TURBO | CCLKCFG_FCS),
+	  "r"(ramstart), "r"(preset_mdrefr),
+	  "r"(postset_mdrefr)
+	: "r4", "r5");
+	local_irq_restore(flags);
+
+	/*
+	 * Tell everyone what we've just done...
+	 * you should add a notify client with any platform specific
+	 * SDRAM refresh timer adjustments
+	 */
+	cpufreq_notify_transition(&freqs, CPUFREQ_POSTCHANGE);
+
+	return 0;
+}
+
+static unsigned int pxa_cpufreq_get(unsigned int cpu)
+{
+	return get_clk_frequency_khz(0);
+}
+
+static int pxa_cpufreq_init(struct cpufreq_policy *policy)
+{
+	int i;
+
+	if (policy->cpu != 0)
+		return -ENODEV;
+
+	/* set default policy and cpuinfo */
+	policy->governor = CPUFREQ_DEFAULT_GOVERNOR;
+	policy->max = policy->cpuinfo.max_freq = max_frequency;
+	policy->min = policy->cpuinfo.min_freq = PXA25x_MIN_FREQ;
+	policy->cpuinfo.transition_latency = 1000000;	/* FIXME: 1 ms, assumed */
+	policy->cur = get_clk_frequency_khz(0);		/* current freq */
+
+	/* Generate the run cpufreq_frequency_table struct */
+	for (i = 0; i < ARRAY_SIZE(pxa25x_performance_freqs); i++) {
+		pxa25x_performance_freq_table[i].frequency = pxa25x_performance_freqs[i].khz;
+		pxa25x_performance_freq_table[i].index = i;
+	}
+	pxa25x_performance_freq_table[i].frequency = CPUFREQ_TABLE_END;
+
+	/* Generate the turbo cpufreq_frequency_table struct */
+	for (i = 0; i < ARRAY_SIZE(pxa25x_powersave_freqs); i++) {
+		pxa25x_powersave_freq_table[i].frequency = pxa25x_powersave_freqs[i].khz;
+		pxa25x_powersave_freq_table[i].index = i;
+	}
+	pxa25x_powersave_freq_table[i].frequency = CPUFREQ_TABLE_END;
+
+	/* calls cpufreq_frequency_table_get_attr */
+	pxa_select_freq_table(policy);
+
+	printk(KERN_INFO "pxa25x: CPU frequency change support initialized (%s tables)\n",
+	       performance ? "performance" : "powersave");
+
+	return 0;
+}
+
+static ssize_t show_pxa25x_freq_model_attr(struct cpufreq_policy *policy, char *buf)
+{
+	return sprintf (buf, "%s\n", performance ? "performance" : "powersave");
+}
+
+static ssize_t store_pxa25x_freq_model_attr(struct cpufreq_policy *policy, const char *buf, size_t count)
+{
+	unsigned int ret;
+	char str[16];
+
+	ret = sscanf(buf, "%15s", str);
+	if (ret != 1)
+		return -EINVAL;
+
+	if (strnicmp(str,"performance",16)==0)
+		performance = 1;
+	else if (strnicmp(str,"powersave",16)==0)
+		performance = 0;
+	else
+		return -EINVAL;
+
+	ret = cpufreq_update_policy(policy->cpu);
+
+	return ret ? ret : count;
+}
+
+struct freq_attr pxa25x_freq_model_attr = {
+	.attr = { .name = "pxa25x_freq_model", .mode = 0644, .owner=THIS_MODULE },
+	.show = show_pxa25x_freq_model_attr,
+	.store = store_pxa25x_freq_model_attr,
+};
+
+static struct freq_attr* pxa_cpufreq_attr[] = {
+	&cpufreq_freq_attr_scaling_available_freqs,
+	&pxa25x_freq_model_attr,
+	NULL,
+};
+
+static struct cpufreq_driver pxa_cpufreq_driver = {
+	.verify	= pxa_verify_policy,
+	.target	= pxa_set_target,
+	.init	= pxa_cpufreq_init,
+	.get	= pxa_cpufreq_get,
+	.name	= "pxa25x",
+	.attr	= pxa_cpufreq_attr,
+};
+
+static int __init pxa_cpu_init(void)
+{
+	return cpufreq_register_driver(&pxa_cpufreq_driver);
+}
+
+static void __exit pxa_cpu_exit(void)
+{
+	cpufreq_unregister_driver(&pxa_cpufreq_driver);
+}
+
+MODULE_AUTHOR("Intrinsyc Software Inc.");
+MODULE_DESCRIPTION("CPU frequency changing driver for the PXA architecture");
+MODULE_LICENSE("GPL");
+module_init(pxa_cpu_init);
+module_exit(pxa_cpu_exit);

-- 
Ian Campbell, Senior Design Engineer
                                        Web: http://www.arcom.com
Arcom, Clifton Road, 			Direct: +44 (0)1223 403 465
Cambridge CB1 7EA, United Kingdom	Phone:  +44 (0)1223 411 200