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authorLv Zheng <lv.zheng@intel.com>2015-02-05 16:27:15 +0800
committerRafael J. Wysocki <rafael.j.wysocki@intel.com>2015-02-05 15:34:51 +0100
commit2eedd3d8398b266ee8e846ded03218bb6a00e2c1 (patch)
tree798b99fda09f7ac7ef46e7488e43af14862231d5 /tools
parenteb3d80f729e07394685239ddd137fbee5c13a2ea (diff)
ACPICA: Events: Enable APIs to allow interrupt/polling adaptive request based GPE handling model
ACPICA commit da9a83e1a845f2d7332bdbc0632466b2595e5424 For acpi_set_gpe()/acpi_enable_gpe(), our target is to purify them to be APIs that can be used for various GPE handling models, so we need them to be pure GPE enabling APIs. GPE enabling/disabling has 2 use cases: 1. Driver may permanently enable/disable GPEs according to the usage counts. 1. When upper layers (the users of the driver) submit requests to the driver, it means they care about the underlying hardware. GPE need to be enabled for the first request submission and disabled for the last request completion. 2. When the GPE is shared between 2+ silicon logics. GPE need to be enabled for either silicon logic's driver and disabled when all of the drivers are not started. For these cases, acpi_enable_gpe()/acpi_disable_gpe() should be used. When the usage count is increased from 0 to 1, the GPE is enabled and it is disabled when the usage count is decrased from 1 to 0. 2. Driver may temporarily disables the GPE to enter an GPE polling mode and wants to re-enable it later. 1. Prevent GPE storming: when a driver cannot fully solve the condition that triggered the GPE in the GPE context, in order not to trigger GPE storm, driver has to disable GPE to switch into the polling mode and re-enables it in the non interrupt context after the storming condition is cleared. 2. Meet throughput requirement: some IO drivers need to poll hardware again and again until nothing indicated instead of just handling once for one interruption, this need to be done in the polling mode or the IO flood may prevent the GPE handler from returning. 3. Meet realtime requirement: in order not to block CPU to handle higher realtime prioritized GPEs, lower priority GPEs can be handled in the polling mode. For these cases, acpi_set_gpe() should be used to switch to/from the polling mode. This patch adds unconditional GPE enabling support into acpi_set_gpe() so that this API can be used by the drivers to switch back from the GPE polling mode unconditionally. Originally this function includes GPE clearing logic in it. First, the GPE clearing is typically used in the GPE handling code to: 1. Acknowledge the GPE when we know there is an edge triggered GPE raised and is about to handle it, otherwise the unexpected clearing may lead to a GPE loss; 2. Issue actions after we have handled a level triggered GPE, otherwise the unexpected clearing may trigger unwanted OSPM actions to the hardware (for example, clocking in out-dated write FIFO data). Thus the GPE clearing is not suitable to be used in the GPE enabling APIs. Second, the combination of acknowledging and enabling may also not be expected by the hardware drivers. For GPE clearing, we have a seperate API acpi_clear_gpe(). There are cases drivers do want the 2 operations to be split. So splitting these 2 operations could facilitates drivers the maximum possibilities to achieve success. For a combined one, we already have acpi_finish_gpe() ready to be invoked. Given the fact that drivers should complete all outstanding requests before putting themselves into the sleep states, as this API is executed for outstanding requests, it should also have nothing to do with the "RUN"/"WAKE" distinguishing. That's why the acpi_set_gpe(ACPI_GPE_ENABLE) should not be implemented by acpi_hw_low_set_gpe(ACPI_GPE_CONDITIONAL_ENABLE). This patch thus converts acpi_set_gpe(ACPI_GPE_ENABLE) into acpi_hw_low_set_gpe(ACPI_GPE_ENABLE) to achieve a seperate GPE enabling API. Drivers then are encouraged to use this API when they need to switch to/from the GPE polling mode. Note that the acpi_set_gpe()/acpi_finish_gpe() should be first introduced to Linux using a divergence reduction patch before sending a linuxized version of this patch. Lv Zheng. Link: https://github.com/acpica/acpica/commit/da9a83e1 Signed-off-by: Lv Zheng <lv.zheng@intel.com> Signed-off-by: David E. Box <david.e.box@linux.intel.com> Signed-off-by: Bob Moore <robert.moore@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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