/*
   *  Copyright (C) 2011 Dmitry Eremin-Solenikov
   *  Copyright (C) 2002 - 2005 Benjamin Herrenschmidt <benh@kernel.crashing.org>
   *  and                       Markus Demleitner <msdemlei@cl.uni-heidelberg.de>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.
   *
   * This driver adds basic cpufreq support for SMU & 970FX based G5 Macs,
   * that is iMac G5 and latest single CPU desktop.
   */
  
  #undef DEBUG
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/errno.h>
  #include <linux/kernel.h>
  #include <linux/delay.h>
  #include <linux/sched.h>
  #include <linux/cpufreq.h>
  #include <linux/init.h>
  #include <linux/completion.h>
  #include <linux/mutex.h>
  #include <linux/time.h>
  #include <linux/of_device.h>
  
  #define DBG(fmt...) pr_debug(fmt)
  
  /* see 970FX user manual */
  
  #define SCOM_PCR 0x0aa001			/* PCR scom addr */
  
  #define PCR_HILO_SELECT		0x80000000U	/* 1 = PCR, 0 = PCRH */
  #define PCR_SPEED_FULL		0x00000000U	/* 1:1 speed value */
  #define PCR_SPEED_HALF		0x00020000U	/* 1:2 speed value */
  #define PCR_SPEED_QUARTER	0x00040000U	/* 1:4 speed value */
  #define PCR_SPEED_MASK		0x000e0000U	/* speed mask */
  #define PCR_SPEED_SHIFT		17
  #define PCR_FREQ_REQ_VALID	0x00010000U	/* freq request valid */
  #define PCR_VOLT_REQ_VALID	0x00008000U	/* volt request valid */
  #define PCR_TARGET_TIME_MASK	0x00006000U	/* target time */
  #define PCR_STATLAT_MASK	0x00001f00U	/* STATLAT value */
  #define PCR_SNOOPLAT_MASK	0x000000f0U	/* SNOOPLAT value */
  #define PCR_SNOOPACC_MASK	0x0000000fU	/* SNOOPACC value */
  
  #define SCOM_PSR 0x408001			/* PSR scom addr */
  /* warning: PSR is a 64 bits register */
  #define PSR_CMD_RECEIVED	0x2000000000000000U   /* command received */
  #define PSR_CMD_COMPLETED	0x1000000000000000U   /* command completed */
  #define PSR_CUR_SPEED_MASK	0x0300000000000000U   /* current speed */
  #define PSR_CUR_SPEED_SHIFT	(56)
  
  /*
   * The G5 only supports two frequencies (Quarter speed is not supported)
   */
  #define CPUFREQ_HIGH                  0
  #define CPUFREQ_LOW                   1
  
  static struct cpufreq_frequency_table maple_cpu_freqs[] = {
  	{0, CPUFREQ_HIGH,		0},
  	{0, CPUFREQ_LOW,		0},
  	{0, 0,				CPUFREQ_TABLE_END},
  };
  
  /* Power mode data is an array of the 32 bits PCR values to use for
   * the various frequencies, retrieved from the device-tree
   */
  static int maple_pmode_cur;
  
  static const u32 *maple_pmode_data;
  static int maple_pmode_max;
  
  /*
   * SCOM based frequency switching for 970FX rev3
   */
  static int maple_scom_switch_freq(int speed_mode)
  {
  	unsigned long flags;
  	int to;
  
  	local_irq_save(flags);
  
  	/* Clear PCR high */
  	scom970_write(SCOM_PCR, 0);
  	/* Clear PCR low */
  	scom970_write(SCOM_PCR, PCR_HILO_SELECT | 0);
  	/* Set PCR low */
  	scom970_write(SCOM_PCR, PCR_HILO_SELECT |
  		      maple_pmode_data[speed_mode]);
  
  	/* Wait for completion */
  	for (to = 0; to < 10; to++) {
  		unsigned long psr = scom970_read(SCOM_PSR);
  
  		if ((psr & PSR_CMD_RECEIVED) == 0 &&
  		    (((psr >> PSR_CUR_SPEED_SHIFT) ^
  		      (maple_pmode_data[speed_mode] >> PCR_SPEED_SHIFT)) & 0x3)
  		    == 0)
  			break;
  		if (psr & PSR_CMD_COMPLETED)
  			break;
  		udelay(100);
  	}
  
  	local_irq_restore(flags);
  
  	maple_pmode_cur = speed_mode;
  	ppc_proc_freq = maple_cpu_freqs[speed_mode].frequency * 1000ul;
  
  	return 0;
  }
  
  static int maple_scom_query_freq(void)
  {
  	unsigned long psr = scom970_read(SCOM_PSR);
  	int i;
  
  	for (i = 0; i <= maple_pmode_max; i++)
  		if ((((psr >> PSR_CUR_SPEED_SHIFT) ^
  		      (maple_pmode_data[i] >> PCR_SPEED_SHIFT)) & 0x3) == 0)
  			break;
  	return i;
  }
  
  /*
   * Common interface to the cpufreq core
   */
  
  static int maple_cpufreq_target(struct cpufreq_policy *policy,
  	unsigned int index)
  {
  	return maple_scom_switch_freq(index);
  }
  
  static unsigned int maple_cpufreq_get_speed(unsigned int cpu)
  {
  	return maple_cpu_freqs[maple_pmode_cur].frequency;
  }
  
  static int maple_cpufreq_cpu_init(struct cpufreq_policy *policy)
  {
  	return cpufreq_generic_init(policy, maple_cpu_freqs, 12000);
  }
  
  static struct cpufreq_driver maple_cpufreq_driver = {
  	.name		= "maple",
  	.flags		= CPUFREQ_CONST_LOOPS,
  	.init		= maple_cpufreq_cpu_init,
  	.verify		= cpufreq_generic_frequency_table_verify,
  	.target_index	= maple_cpufreq_target,
  	.get		= maple_cpufreq_get_speed,
  	.attr		= cpufreq_generic_attr,
  };
  
  static int __init maple_cpufreq_init(void)
  {
  	struct device_node *cpunode;
  	unsigned int psize;
  	unsigned long max_freq;
  	const u32 *valp;
  	u32 pvr_hi;
  	int rc = -ENODEV;
  
  	/*
  	 * Behave here like powermac driver which checks machine compatibility
  	 * to ease merging of two drivers in future.
  	 */
  	if (!of_machine_is_compatible("Momentum,Maple") &&
  	    !of_machine_is_compatible("Momentum,Apache"))
  		return 0;
  
  	/* Get first CPU node */
  	cpunode = of_cpu_device_node_get(0);
  	if (cpunode == NULL) {
  		printk(KERN_ERR "cpufreq: Can't find any CPU 0 node
  ");
  		goto bail_noprops;
  	}
  
  	/* Check 970FX for now */
  	/* we actually don't care on which CPU to access PVR */
  	pvr_hi = PVR_VER(mfspr(SPRN_PVR));
  	if (pvr_hi != 0x3c && pvr_hi != 0x44) {
  		printk(KERN_ERR "cpufreq: Unsupported CPU version (%x)
  ",
  				pvr_hi);
  		goto bail_noprops;
  	}
  
  	/* Look for the powertune data in the device-tree */
  	/*
  	 * On Maple this property is provided by PIBS in dual-processor config,
  	 * not provided by PIBS in CPU0 config and also not provided by SLOF,
  	 * so YMMV
  	 */
  	maple_pmode_data = of_get_property(cpunode, "power-mode-data", &psize);
  	if (!maple_pmode_data) {
  		DBG("No power-mode-data !
  ");
  		goto bail_noprops;
  	}
  	maple_pmode_max = psize / sizeof(u32) - 1;
  
  	/*
  	 * From what I see, clock-frequency is always the maximal frequency.
  	 * The current driver can not slew sysclk yet, so we really only deal
  	 * with powertune steps for now. We also only implement full freq and
  	 * half freq in this version. So far, I haven't yet seen a machine
  	 * supporting anything else.
  	 */
  	valp = of_get_property(cpunode, "clock-frequency", NULL);
  	if (!valp)
  		return -ENODEV;
  	max_freq = (*valp)/1000;
  	maple_cpu_freqs[0].frequency = max_freq;
  	maple_cpu_freqs[1].frequency = max_freq/2;
  
  	/* Force apply current frequency to make sure everything is in
  	 * sync (voltage is right for example). Firmware may leave us with
  	 * a strange setting ...
  	 */
  	msleep(10);
  	maple_pmode_cur = -1;
  	maple_scom_switch_freq(maple_scom_query_freq());
  
  	printk(KERN_INFO "Registering Maple CPU frequency driver
  ");
  	printk(KERN_INFO "Low: %d Mhz, High: %d Mhz, Cur: %d MHz
  ",
  		maple_cpu_freqs[1].frequency/1000,
  		maple_cpu_freqs[0].frequency/1000,
  		maple_cpu_freqs[maple_pmode_cur].frequency/1000);
  
  	rc = cpufreq_register_driver(&maple_cpufreq_driver);
  
  	of_node_put(cpunode);
  
  	return rc;
  
  bail_noprops:
  	of_node_put(cpunode);
  
  	return rc;
  }
  
  module_init(maple_cpufreq_init);
  
  
  MODULE_LICENSE("GPL");