// SPDX-License-Identifier: GPL-2.0-only

  /*
   * Intel SpeedStep SMI driver.
   *
   * (C) 2003  Hiroshi Miura <miura@da-cha.org>

   */
  
  
  /*********************************************************************
   *                        SPEEDSTEP - DEFINITIONS                    *
   *********************************************************************/

  #define pr_fmt(fmt) "cpufreq: " fmt

  #include <linux/kernel.h>

  #include <linux/module.h>
  #include <linux/moduleparam.h>

  #include <linux/init.h>
  #include <linux/cpufreq.h>

  #include <linux/delay.h>

  #include <linux/io.h>

  #include <asm/ist.h>

  #include <asm/cpu_device_id.h>

  
  #include "speedstep-lib.h"
  
  /* speedstep system management interface port/command.
   *
   * These parameters are got from IST-SMI BIOS call.
   * If user gives it, these are used.

   *

   */

  static int smi_port;
  static int smi_cmd;
  static unsigned int smi_sig;

  
  /* info about the processor */

  static enum speedstep_processor speedstep_processor;

  /*
   * There are only two frequency states for each processor. Values

   * are in kHz for the time being.
   */
  static struct cpufreq_frequency_table speedstep_freqs[] = {

  	{0, SPEEDSTEP_HIGH,	0},
  	{0, SPEEDSTEP_LOW,	0},
  	{0, 0,			CPUFREQ_TABLE_END},

  };
  
  #define GET_SPEEDSTEP_OWNER 0
  #define GET_SPEEDSTEP_STATE 1
  #define SET_SPEEDSTEP_STATE 2
  #define GET_SPEEDSTEP_FREQS 4
  
  /* how often shall the SMI call be tried if it failed, e.g. because
   * of DMA activity going on? */
  #define SMI_TRIES 5

  /**
   * speedstep_smi_ownership
   */

  static int speedstep_smi_ownership(void)

  {

  	u32 command, result, magic, dummy;

  	u32 function = GET_SPEEDSTEP_OWNER;
  	unsigned char magic_data[] = "Copyright (c) 1999 Intel Corporation";
  
  	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);
  	magic = virt_to_phys(magic_data);

  	pr_debug("trying to obtain ownership with command %x at port %x
  ",

  			command, smi_port);

  
  	__asm__ __volatile__(

  		"push %%ebp
  "

  		"out %%al, (%%dx)
  "

  		"pop %%ebp
  "

  		: "=D" (result),
  		  "=a" (dummy), "=b" (dummy), "=c" (dummy), "=d" (dummy),
  		  "=S" (dummy)

  		: "a" (command), "b" (function), "c" (0), "d" (smi_port),

  		  "D" (0), "S" (magic)

  		: "memory"

  	);

  	pr_debug("result is %x
  ", result);

  
  	return result;
  }
  
  /**
   * speedstep_smi_get_freqs - get SpeedStep preferred & current freq.
   * @low: the low frequency value is placed here
   * @high: the high frequency value is placed here
   *
   * Only available on later SpeedStep-enabled systems, returns false results or
   * even hangs [cf. bugme.osdl.org # 1422] on earlier systems. Empirical testing
   * shows that the latter occurs if !(ist_info.event & 0xFFFF).
   */

  static int speedstep_smi_get_freqs(unsigned int *low, unsigned int *high)

  {

  	u32 command, result = 0, edi, high_mhz, low_mhz, dummy;

  	u32 state = 0;

  	u32 function = GET_SPEEDSTEP_FREQS;
  
  	if (!(ist_info.event & 0xFFFF)) {

  		pr_debug("bug #1422 -- can't read freqs from BIOS
  ");

  		return -ENODEV;
  	}
  
  	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);

  	pr_debug("trying to determine frequencies with command %x at port %x
  ",

  			command, smi_port);

  	__asm__ __volatile__(
  		"push %%ebp
  "

  		"out %%al, (%%dx)
  "

  		"pop %%ebp"

  		: "=a" (result),
  		  "=b" (high_mhz),
  		  "=c" (low_mhz),
  		  "=d" (state), "=D" (edi), "=S" (dummy)
  		: "a" (command),
  		  "b" (function),
  		  "c" (state),
  		  "d" (smi_port), "S" (0), "D" (0)

  	);

  	pr_debug("result %x, low_freq %u, high_freq %u
  ",

  			result, low_mhz, high_mhz);

  
  	/* abort if results are obviously incorrect... */
  	if ((high_mhz + low_mhz) < 600)
  		return -EINVAL;
  
  	*high = high_mhz * 1000;
  	*low  = low_mhz  * 1000;
  
  	return result;

  }

  
  /**

   * speedstep_set_state - set the SpeedStep state
   * @state: new processor frequency state (SPEEDSTEP_LOW or SPEEDSTEP_HIGH)
   *
   */

  static void speedstep_set_state(unsigned int state)

  {

  	unsigned int result = 0, command, new_state, dummy;

  	unsigned long flags;

  	unsigned int function = SET_SPEEDSTEP_STATE;

  	unsigned int retry = 0;
  
  	if (state > 0x1)
  		return;
  
  	/* Disable IRQs */

  	preempt_disable();

  	local_irq_save(flags);
  
  	command = (smi_sig & 0xffffff00) | (smi_cmd & 0xff);

  	pr_debug("trying to set frequency to state %u "

  		"with command %x at port %x
  ",
  		state, command, smi_port);

  
  	do {
  		if (retry) {

  			/*
  			 * We need to enable interrupts, otherwise the blockage
  			 * won't resolve.
  			 *
  			 * We disable preemption so that other processes don't
  			 * run. If other processes were running, they could
  			 * submit more DMA requests, making the blockage worse.
  			 */

  			pr_debug("retry %u, previous result %u, waiting...
  ",

  					retry, result);

  			local_irq_enable();

  			mdelay(retry * 50);

  			local_irq_disable();

  		}
  		retry++;
  		__asm__ __volatile__(

  			"push %%ebp
  "

  			"out %%al, (%%dx)
  "

  			"pop %%ebp"

  			: "=b" (new_state), "=D" (result),
  			  "=c" (dummy), "=a" (dummy),
  			  "=d" (dummy), "=S" (dummy)
  			: "a" (command), "b" (function), "c" (state),
  			  "d" (smi_port), "S" (0), "D" (0)

  			);
  	} while ((new_state != state) && (retry <= SMI_TRIES));
  
  	/* enable IRQs */
  	local_irq_restore(flags);

  	preempt_enable();

  	if (new_state == state)

  		pr_debug("change to %u MHz succeeded after %u tries "

  			"with result %u
  ",
  			(speedstep_freqs[new_state].frequency / 1000),
  			retry, result);
  	else

  		pr_err("change to state %u failed with new_state %u and result %u
  ",

  		       state, new_state, result);

  
  	return;
  }
  
  
  /**
   * speedstep_target - set a new CPUFreq policy
   * @policy: new policy

   * @index: index of new freq

   *
   * Sets a new CPUFreq policy/freq.
   */

  static int speedstep_target(struct cpufreq_policy *policy, unsigned int index)

  {

  	speedstep_set_state(index);

  
  	return 0;
  }

  static int speedstep_cpu_init(struct cpufreq_policy *policy)
  {
  	int result;

  	unsigned int *low, *high;

  
  	/* capability check */
  	if (policy->cpu != 0)
  		return -ENODEV;
  
  	result = speedstep_smi_ownership();
  	if (result) {

  		pr_debug("fails in acquiring ownership of a SMI interface.
  ");

  		return -EINVAL;
  	}
  
  	/* detect low and high frequency */

  	low = &speedstep_freqs[SPEEDSTEP_LOW].frequency;
  	high = &speedstep_freqs[SPEEDSTEP_HIGH].frequency;
  
  	result = speedstep_smi_get_freqs(low, high);

  	if (result) {

  		/* fall back to speedstep_lib.c dection mechanism:
  		 * try both states out */

  		pr_debug("could not detect low and high frequencies "

  				"by SMI call.
  ");

  		result = speedstep_get_freqs(speedstep_processor,

  				low, high,

  				NULL,

  				&speedstep_set_state);
  
  		if (result) {

  			pr_debug("could not detect two different speeds"

  					" -- aborting.
  ");

  			return result;
  		} else

  			pr_debug("workaround worked.
  ");

  	}

  	policy->freq_table = speedstep_freqs;
  
  	return 0;

  }

  static unsigned int speedstep_get(unsigned int cpu)
  {
  	if (cpu)
  		return -ENODEV;

  	return speedstep_get_frequency(speedstep_processor);

  }
  
  
  static int speedstep_resume(struct cpufreq_policy *policy)
  {
  	int result = speedstep_smi_ownership();
  
  	if (result)

  		pr_debug("fails in re-acquiring ownership of a SMI interface.
  ");

  
  	return result;
  }

  static struct cpufreq_driver speedstep_driver = {

  	.name		= "speedstep-smi",

  	.flags		= CPUFREQ_NO_AUTO_DYNAMIC_SWITCHING,

  	.verify		= cpufreq_generic_frequency_table_verify,

  	.target_index	= speedstep_target,

  	.init		= speedstep_cpu_init,

  	.get		= speedstep_get,
  	.resume		= speedstep_resume,

  	.attr		= cpufreq_generic_attr,

  };

  static const struct x86_cpu_id ss_smi_ids[] = {

  	X86_MATCH_VENDOR_FAM_MODEL(INTEL,  6, 0x8, 0),
  	X86_MATCH_VENDOR_FAM_MODEL(INTEL,  6, 0xb, 0),
  	X86_MATCH_VENDOR_FAM_MODEL(INTEL, 15, 0x2, 0),

  	{}
  };

  /**
   * speedstep_init - initializes the SpeedStep CPUFreq driver
   *
   *   Initializes the SpeedStep support. Returns -ENODEV on unsupported
   * BIOS, -EINVAL on problems during initiatization, and zero on
   * success.
   */
  static int __init speedstep_init(void)
  {

  	if (!x86_match_cpu(ss_smi_ids))
  		return -ENODEV;

  	speedstep_processor = speedstep_detect_processor();
  
  	switch (speedstep_processor) {

  	case SPEEDSTEP_CPU_PIII_T:
  	case SPEEDSTEP_CPU_PIII_C:
  	case SPEEDSTEP_CPU_PIII_C_EARLY:

  		break;
  	default:
  		speedstep_processor = 0;
  	}
  
  	if (!speedstep_processor) {

  		pr_debug("No supported Intel CPU detected.
  ");

  		return -ENODEV;
  	}

  	pr_debug("signature:0x%.8x, command:0x%.8x, "
  		"event:0x%.8x, perf_level:0x%.8x.
  ",

  		ist_info.signature, ist_info.command,
  		ist_info.event, ist_info.perf_level);

  	/* Error if no IST-SMI BIOS or no PARM

  		 sig= 'ISGE' aka 'Intel Speedstep Gate E' */

  	if ((ist_info.signature !=  0x47534943) && (

  	    (smi_port == 0) || (smi_cmd == 0)))
  		return -ENODEV;
  
  	if (smi_sig == 1)
  		smi_sig = 0x47534943;
  	else
  		smi_sig = ist_info.signature;
  
  	/* setup smi_port from MODLULE_PARM or BIOS */

  	if ((smi_port > 0xff) || (smi_port < 0))

  		return -EINVAL;

  	else if (smi_port == 0)

  		smi_port = ist_info.command & 0xff;

  	if ((smi_cmd > 0xff) || (smi_cmd < 0))

  		return -EINVAL;

  	else if (smi_cmd == 0)

  		smi_cmd = (ist_info.command >> 16) & 0xff;

  
  	return cpufreq_register_driver(&speedstep_driver);
  }
  
  
  /**
   * speedstep_exit - unregisters SpeedStep support
   *
   *   Unregisters SpeedStep support.
   */
  static void __exit speedstep_exit(void)
  {
  	cpufreq_unregister_driver(&speedstep_driver);
  }

  module_param_hw(smi_port, int, ioport, 0444);

  module_param(smi_cmd,  int, 0444);
  module_param(smi_sig, uint, 0444);

  MODULE_PARM_DESC(smi_port, "Override the BIOS-given IST port with this value "
  		"-- Intel's default setting is 0xb2");
  MODULE_PARM_DESC(smi_cmd, "Override the BIOS-given IST command with this value "
  		"-- Intel's default setting is 0x82");
  MODULE_PARM_DESC(smi_sig, "Set to 1 to fake the IST signature when using the "
  		"SMI interface.");

  MODULE_AUTHOR("Hiroshi Miura");
  MODULE_DESCRIPTION("Speedstep driver for IST applet SMI interface.");
  MODULE_LICENSE("GPL");

  
  module_init(speedstep_init);
  module_exit(speedstep_exit);