OMAP2/3 PM: create the OMAP PM interface and add a default OMAP PM no-op layer

The OMAP PM interface

=====================

This document describes the temporary OMAP PM interface.  Driver

authors use these functions to communicate minimum latency or

throughput constraints to the kernel power management code.

Over time, the intention is to merge features from the OMAP PM

interface into the Linux PM QoS code.

Drivers need to express PM parameters which:

- support the range of power management parameters present in the TI SRF;

- separate the drivers from the underlying PM parameter

  implementation, whether it is the TI SRF or Linux PM QoS or Linux

  latency framework or something else;

- specify PM parameters in terms of fundamental units, such as

  latency and throughput, rather than units which are specific to OMAP

  or to particular OMAP variants;

- allow drivers which are shared with other architectures (e.g.,

  DaVinci) to add these constraints in a way which won't affect non-OMAP

  systems,

- can be implemented immediately with minimal disruption of other

  architectures.

This document proposes the OMAP PM interface, including the following

five power management functions for driver code:

1. Set the maximum MPU wakeup latency:

   (*pdata->set_max_mpu_wakeup_lat)(struct device *dev, unsigned long t)

2. Set the maximum device wakeup latency:

   (*pdata->set_max_dev_wakeup_lat)(struct device *dev, unsigned long t)

3. Set the maximum system DMA transfer start latency (CORE pwrdm):

   (*pdata->set_max_sdma_lat)(struct device *dev, long t)

4. Set the minimum bus throughput needed by a device:

   (*pdata->set_min_bus_tput)(struct device *dev, u8 agent_id, unsigned long r)

5. Return the number of times the device has lost context

   (*pdata->get_dev_context_loss_count)(struct device *dev)

Further documentation for all OMAP PM interface functions can be

found in arch/arm/plat-omap/include/mach/omap-pm.h.

The OMAP PM layer is intended to be temporary

---------------------------------------------

The intention is that eventually the Linux PM QoS layer should support

the range of power management features present in OMAP3.  As this

happens, existing drivers using the OMAP PM interface can be modified

to use the Linux PM QoS code; and the OMAP PM interface can disappear.

Driver usage of the OMAP PM functions

-------------------------------------

As the 'pdata' in the above examples indicates, these functions are

exposed to drivers through function pointers in driver .platform_data

structures.  The function pointers are initialized by the board-*.c

files to point to the corresponding OMAP PM functions:

.set_max_dev_wakeup_lat will point to

omap_pm_set_max_dev_wakeup_lat(), etc.  Other architectures which do

not support these functions should leave these function pointers set

to NULL.  Drivers should use the following idiom:

        if (pdata->set_max_dev_wakeup_lat)

            (*pdata->set_max_dev_wakeup_lat)(dev, t);

The most common usage of these functions will probably be to specify

the maximum time from when an interrupt occurs, to when the device

becomes accessible.  To accomplish this, driver writers should use the

set_max_mpu_wakeup_lat() function to to constrain the MPU wakeup

latency, and the set_max_dev_wakeup_lat() function to constrain the

device wakeup latency (from clk_enable() to accessibility).  For

example,

        /* Limit MPU wakeup latency */

        if (pdata->set_max_mpu_wakeup_lat)

            (*pdata->set_max_mpu_wakeup_lat)(dev, tc);

        /* Limit device powerdomain wakeup latency */

        if (pdata->set_max_dev_wakeup_lat)

            (*pdata->set_max_dev_wakeup_lat)(dev, td);

        /* total wakeup latency in this example: (tc + td) */

The PM parameters can be overwritten by calling the function again

with the new value.  The settings can be removed by calling the

function with a t argument of -1 (except in the case of

set_max_bus_tput(), which should be called with an r argument of 0).

The fifth function above, omap_pm_get_dev_context_loss_count(),

is intended as an optimization to allow drivers to determine whether the

device has lost its internal context.  If context has been lost, the

driver must restore its internal context before proceeding.

Other specialized interface functions

-------------------------------------

The five functions listed above are intended to be usable by any

device driver.  DSPBridge and CPUFreq have a few special requirements.

DSPBridge expresses target DSP performance levels in terms of OPP IDs.

CPUFreq expresses target MPU performance levels in terms of MPU

frequency.  The OMAP PM interface contains functions for these

specialized cases to convert that input information (OPPs/MPU

frequency) into the form that the underlying power management

implementation needs:

6. (*pdata->dsp_get_opp_table)(void)

7. (*pdata->dsp_set_min_opp)(u8 opp_id)

8. (*pdata->dsp_get_opp)(void)

9. (*pdata->cpu_get_freq_table)(void)

10. (*pdata->cpu_set_freq)(unsigned long f)

11. (*pdata->cpu_get_freq)(void)

#ifndef CONFIG_ARCH_OMAP4	/* FIXME: Remove this once clkdev is ready */

#include "clock.h"

#include <mach/omap-pm.h>

#include <mach/powerdomain.h>

#include "powerdomains.h"

{

	omap2_mux_init();

#ifndef CONFIG_ARCH_OMAP4 /* FIXME: Remove this once the clkdev is ready */

	/* The OPP tables have to be registered before a clk init */

	omap_pm_if_early_init(mpu_opps, dsp_opps, l3_opps);

	pwrdm_init(powerdomains_omap);

	clkdm_init(clockdomains_omap, clkdm_pwrdm_autodeps);

	omap2_clk_init();

	omap_pm_if_init();

	omap2_sdrc_init(sdrc_cs0, sdrc_cs1);

	_omap2_init_reprogram_sdrc();

#endif

	  to data on the serial RX line. This allows you to wake the

	  system from serial console.

choice

	prompt "OMAP PM layer selection"

	depends on ARCH_OMAP

	default OMAP_PM_NOOP

config OMAP_PM_NONE

	bool "No PM layer"

config OMAP_PM_NOOP

	bool "No-op/debug PM layer"

endchoice

endmenu

endif

# OMAP mailbox framework

obj-$(CONFIG_OMAP_MBOX_FWK) += mailbox.o

obj-$(CONFIG_OMAP_PM_NOOP) += omap-pm-noop.o

 No newline at end of file

/*

 * omap-pm.h - OMAP power management interface

 *

 * Copyright (C) 2008-2009 Texas Instruments, Inc.

 * Copyright (C) 2008-2009 Nokia Corporation

 * Paul Walmsley

 *

 * Interface developed by (in alphabetical order): Karthik Dasu, Jouni

 * Högander, Tony Lindgren, Rajendra Nayak, Sakari Poussa,

 * Veeramanikandan Raju, Anand Sawant, Igor Stoppa, Paul Walmsley,

 * Richard Woodruff

 */

#ifndef ASM_ARM_ARCH_OMAP_OMAP_PM_H

#define ASM_ARM_ARCH_OMAP_OMAP_PM_H

#include <linux/device.h>

#include <linux/cpufreq.h>

#include "powerdomain.h"

/**

 * struct omap_opp - clock frequency-to-OPP ID table for DSP, MPU

 * @rate: target clock rate

 * @opp_id: OPP ID

 * @min_vdd: minimum VDD1 voltage (in millivolts) for this OPP

 *

 * Operating performance point data.  Can vary by OMAP chip and board.

 */

struct omap_opp {

	unsigned long rate;

	u8 opp_id;

	u16 min_vdd;

};

extern struct omap_opp *mpu_opps;

extern struct omap_opp *dsp_opps;

extern struct omap_opp *l3_opps;

/*

 * agent_id values for use with omap_pm_set_min_bus_tput():

 *

 * OCP_INITIATOR_AGENT is only valid for devices that can act as

 * initiators -- it represents the device's L3 interconnect

 * connection.  OCP_TARGET_AGENT represents the device's L4

 * interconnect connection.

 */

#define OCP_TARGET_AGENT		1

#define OCP_INITIATOR_AGENT		2

/**

 * omap_pm_if_early_init - OMAP PM init code called before clock fw init

 * @mpu_opp_table: array ptr to struct omap_opp for MPU

 * @dsp_opp_table: array ptr to struct omap_opp for DSP

 * @l3_opp_table : array ptr to struct omap_opp for CORE

 *

 * Initialize anything that must be configured before the clock

 * framework starts.  The "_if_" is to avoid name collisions with the

 * PM idle-loop code.

 */

int __init omap_pm_if_early_init(struct omap_opp *mpu_opp_table,

				 struct omap_opp *dsp_opp_table,

				 struct omap_opp *l3_opp_table);

/**

 * omap_pm_if_init - OMAP PM init code called after clock fw init

 *

 * The main initialization code.  OPP tables are passed in here.  The

 * "_if_" is to avoid name collisions with the PM idle-loop code.

 */

int __init omap_pm_if_init(void);

/**

 * omap_pm_if_exit - OMAP PM exit code

 *

 * Exit code; currently unused.  The "_if_" is to avoid name

 * collisions with the PM idle-loop code.

 */

void omap_pm_if_exit(void);

/*

 * Device-driver-originated constraints (via board-*.c files, platform_data)

 */

/**

 * omap_pm_set_max_mpu_wakeup_lat - set the maximum MPU wakeup latency

 * @dev: struct device * requesting the constraint

 * @t: maximum MPU wakeup latency in microseconds

 *

 * Request that the maximum interrupt latency for the MPU to be no

 * greater than 't' microseconds. "Interrupt latency" in this case is

 * defined as the elapsed time from the occurrence of a hardware or

 * timer interrupt to the time when the device driver's interrupt

 * service routine has been entered by the MPU.

 *

 * It is intended that underlying PM code will use this information to

 * determine what power state to put the MPU powerdomain into, and

 * possibly the CORE powerdomain as well, since interrupt handling

 * code currently runs from SDRAM.  Advanced PM or board*.c code may

 * also configure interrupt controller priorities, OCP bus priorities,

 * CPU speed(s), etc.

 *

 * This function will not affect device wakeup latency, e.g., time

 * elapsed from when a device driver enables a hardware device with

 * clk_enable(), to when the device is ready for register access or

 * other use.  To control this device wakeup latency, use

 * set_max_dev_wakeup_lat()

 *

 * Multiple calls to set_max_mpu_wakeup_lat() will replace the

 * previous t value.  To remove the latency target for the MPU, call

 * with t = -1.

 *

 * No return value.

 */

void omap_pm_set_max_mpu_wakeup_lat(struct device *dev, long t);

/**

 * omap_pm_set_min_bus_tput - set minimum bus throughput needed by device

 * @dev: struct device * requesting the constraint

 * @tbus_id: interconnect to operate on (OCP_{INITIATOR,TARGET}_AGENT)

 * @r: minimum throughput (in KiB/s)

 *

 * Request that the minimum data throughput on the OCP interconnect

 * attached to device 'dev' interconnect agent 'tbus_id' be no less

 * than 'r' KiB/s.

 *

 * It is expected that the OMAP PM or bus code will use this

 * information to set the interconnect clock to run at the lowest

 * possible speed that satisfies all current system users.  The PM or

 * bus code will adjust the estimate based on its model of the bus, so

 * device driver authors should attempt to specify an accurate

 * quantity for their device use case, and let the PM or bus code

 * overestimate the numbers as necessary to handle request/response

 * latency, other competing users on the system, etc.  On OMAP2/3, if

 * a driver requests a minimum L4 interconnect speed constraint, the

 * code will also need to add an minimum L3 interconnect speed

 * constraint,

 *

 * Multiple calls to set_min_bus_tput() will replace the previous rate

 * value for this device.  To remove the interconnect throughput

 * restriction for this device, call with r = 0.

 *

 * No return value.

 */

void omap_pm_set_min_bus_tput(struct device *dev, u8 agent_id, unsigned long r);

/**

 * omap_pm_set_max_dev_wakeup_lat - set the maximum device enable latency

 * @dev: struct device *

 * @t: maximum device wakeup latency in microseconds

 *

 * Request that the maximum amount of time necessary for a device to

 * become accessible after its clocks are enabled should be no greater

 * than 't' microseconds.  Specifically, this represents the time from

 * when a device driver enables device clocks with clk_enable(), to

 * when the register reads and writes on the device will succeed.

 * This function should be called before clk_disable() is called,

 * since the power state transition decision may be made during

 * clk_disable().

 *

 * It is intended that underlying PM code will use this information to

 * determine what power state to put the powerdomain enclosing this

 * device into.

 *

 * Multiple calls to set_max_dev_wakeup_lat() will replace the

 * previous wakeup latency values for this device.  To remove the wakeup

 * latency restriction for this device, call with t = -1.

 *

 * No return value.

 */

void omap_pm_set_max_dev_wakeup_lat(struct device *dev, long t);

/**

 * omap_pm_set_max_sdma_lat - set the maximum system DMA transfer start latency

 * @dev: struct device *

 * @t: maximum DMA transfer start latency in microseconds

 *

 * Request that the maximum system DMA transfer start latency for this

 * device 'dev' should be no greater than 't' microseconds.  "DMA

 * transfer start latency" here is defined as the elapsed time from

 * when a device (e.g., McBSP) requests that a system DMA transfer

 * start or continue, to the time at which data starts to flow into

 * that device from the system DMA controller.

 *

 * It is intended that underlying PM code will use this information to

 * determine what power state to put the CORE powerdomain into.

 *

 * Since system DMA transfers may not involve the MPU, this function

 * will not affect MPU wakeup latency.  Use set_max_cpu_lat() to do

 * so.  Similarly, this function will not affect device wakeup latency

 * -- use set_max_dev_wakeup_lat() to affect that.

 *

 * Multiple calls to set_max_sdma_lat() will replace the previous t

 * value for this device.  To remove the maximum DMA latency for this

 * device, call with t = -1.

 *

 * No return value.

 */

void omap_pm_set_max_sdma_lat(struct device *dev, long t);

/*

 * DSP Bridge-specific constraints

 */

/**

 * omap_pm_dsp_get_opp_table - get OPP->DSP clock frequency table

 *

 * Intended for use by DSPBridge.  Returns an array of OPP->DSP clock

 * frequency entries.  The final item in the array should have .rate =

 * .opp_id = 0.

 */

const struct omap_opp *omap_pm_dsp_get_opp_table(void);

/**

 * omap_pm_dsp_set_min_opp - receive desired OPP target ID from DSP Bridge

 * @opp_id: target DSP OPP ID

 *

 * Set a minimum OPP ID for the DSP.  This is intended to be called

 * only from the DSP Bridge MPU-side driver.  Unfortunately, the only

 * information that code receives from the DSP/BIOS load estimator is the

 * target OPP ID; hence, this interface.  No return value.

 */

void omap_pm_dsp_set_min_opp(u8 opp_id);

/**

 * omap_pm_dsp_get_opp - report the current DSP OPP ID

 *

 * Report the current OPP for the DSP.  Since on OMAP3, the DSP and

 * MPU share a single voltage domain, the OPP ID returned back may

 * represent a higher DSP speed than the OPP requested via

 * omap_pm_dsp_set_min_opp().

 *

 * Returns the current VDD1 OPP ID, or 0 upon error.

 */

u8 omap_pm_dsp_get_opp(void);

/*

 * CPUFreq-originated constraint

 *

 * In the future, this should be handled by custom OPP clocktype

 * functions.

 */

/**

 * omap_pm_cpu_get_freq_table - return a cpufreq_frequency_table array ptr

 *

 * Provide a frequency table usable by CPUFreq for the current chip/board.

 * Returns a pointer to a struct cpufreq_frequency_table array or NULL

 * upon error.

 */

struct cpufreq_frequency_table **omap_pm_cpu_get_freq_table(void);

/**

 * omap_pm_cpu_set_freq - set the current minimum MPU frequency

 * @f: MPU frequency in Hz

 *

 * Set the current minimum CPU frequency.  The actual CPU frequency

 * used could end up higher if the DSP requested a higher OPP.

 * Intended to be called by plat-omap/cpu_omap.c:omap_target().  No

 * return value.

 */

void omap_pm_cpu_set_freq(unsigned long f);

/**

 * omap_pm_cpu_get_freq - report the current CPU frequency

 *

 * Returns the current MPU frequency, or 0 upon error.

 */

unsigned long omap_pm_cpu_get_freq(void);

/*

 * Device context loss tracking

 */

/**

 * omap_pm_get_dev_context_loss_count - return count of times dev has lost ctx

 * @dev: struct device *

 *

 * This function returns the number of times that the device @dev has

 * lost its internal context.  This generally occurs on a powerdomain

 * transition to OFF.  Drivers use this as an optimization to avoid restoring

 * context if the device hasn't lost it.  To use, drivers should initially

 * call this in their context save functions and store the result.  Early in

 * the driver's context restore function, the driver should call this function

 * again, and compare the result to the stored counter.  If they differ, the

 * driver must restore device context.   If the number of context losses

 * exceeds the maximum positive integer, the function will wrap to 0 and

 * continue counting.  Returns the number of context losses for this device,

 * or -EINVAL upon error.

 */

int omap_pm_get_dev_context_loss_count(struct device *dev);

#endif