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Merge branch 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/k…
…ernel/git/tmlind/linux-omap-2.6 * 'omap-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap-2.6: (47 commits) OMAP clock: use debugfs_remove_recursive() for rewinding OMAP2/3/4 core: create omap_device layer OMAP: omap_hwmod: call omap_hwmod init at boot; create interconnects OMAP2/3/4: create omap_hwmod layer OMAP2/3 board-*.c files: read bootloader configuration earlier OMAP2/3/4 PRCM: add module IDLEST wait code OMAP2/3 PM: create the OMAP PM interface and add a default OMAP PM no-op layer OMAP3 clock: remove superfluous calls to omap2_init_clk_clkdm OMAP clock: associate MPU clocks with the mpu_clkdm OMAP3 clock: Fixed processing of bootarg 'mpurate' OMAP: SDRC: Add several new register definitions OMAP: powerdomain: Fix overflow when doing powerdomain deps lookups. OMAP: PM: Added suspend target state control to debugfs for OMAP3 OMAP: PM debug: Add PRCM register dump support OMAP: PM debug: make powerdomains use PM-debug counters OMAP: PM: Add pm-debug counters OMAP: PM: Add closures to clkdm_for_each and pwrdm_for_each. OMAP: PM: Hook into PM counters OMAP: PM counter infrastructure. OMAP3: PM: fix lockdep warning caused by omap3_pm_init ...
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The OMAP PM interface | ||
===================== | ||
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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. | ||
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Drivers need to express PM parameters which: | ||
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- support the range of power management parameters present in the TI SRF; | ||
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- 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; | ||
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- 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; | ||
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- 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, | ||
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- can be implemented immediately with minimal disruption of other | ||
architectures. | ||
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This document proposes the OMAP PM interface, including the following | ||
five power management functions for driver code: | ||
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1. Set the maximum MPU wakeup latency: | ||
(*pdata->set_max_mpu_wakeup_lat)(struct device *dev, unsigned long t) | ||
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2. Set the maximum device wakeup latency: | ||
(*pdata->set_max_dev_wakeup_lat)(struct device *dev, unsigned long t) | ||
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3. Set the maximum system DMA transfer start latency (CORE pwrdm): | ||
(*pdata->set_max_sdma_lat)(struct device *dev, long t) | ||
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4. Set the minimum bus throughput needed by a device: | ||
(*pdata->set_min_bus_tput)(struct device *dev, u8 agent_id, unsigned long r) | ||
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5. Return the number of times the device has lost context | ||
(*pdata->get_dev_context_loss_count)(struct device *dev) | ||
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Further documentation for all OMAP PM interface functions can be | ||
found in arch/arm/plat-omap/include/mach/omap-pm.h. | ||
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The OMAP PM layer is intended to be temporary | ||
--------------------------------------------- | ||
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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. | ||
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Driver usage of the OMAP PM functions | ||
------------------------------------- | ||
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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: | ||
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if (pdata->set_max_dev_wakeup_lat) | ||
(*pdata->set_max_dev_wakeup_lat)(dev, t); | ||
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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, | ||
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/* Limit MPU wakeup latency */ | ||
if (pdata->set_max_mpu_wakeup_lat) | ||
(*pdata->set_max_mpu_wakeup_lat)(dev, tc); | ||
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/* Limit device powerdomain wakeup latency */ | ||
if (pdata->set_max_dev_wakeup_lat) | ||
(*pdata->set_max_dev_wakeup_lat)(dev, td); | ||
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/* total wakeup latency in this example: (tc + td) */ | ||
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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). | ||
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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. | ||
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Other specialized interface functions | ||
------------------------------------- | ||
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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: | ||
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6. (*pdata->dsp_get_opp_table)(void) | ||
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7. (*pdata->dsp_set_min_opp)(u8 opp_id) | ||
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8. (*pdata->dsp_get_opp)(void) | ||
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9. (*pdata->cpu_get_freq_table)(void) | ||
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10. (*pdata->cpu_set_freq)(unsigned long f) | ||
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11. (*pdata->cpu_get_freq)(void) |
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