ACPI / CPPC: optimized cpc_read and cpc_write

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cpc_read and cpc_write are used while holding the pcc_lock spin_lock,
so they need to be as fast as possible. acpi_os_read/write_memory
APIs linearly search through a list for cached mapping which is
quite expensive. Since the PCC subspace is already mapped into
virtual address space during initialization, we can just add the
offset and access the necessary CPPC registers.

This patch + similar changes to PCC driver reduce the time per freq.
transition from around 200us to about 20us for the CPPC cpufreq
driver.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Acked-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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Prakash, Prashanth 2016-02-17 13:21:00 -07:00 • committed by Rafael J. Wysocki

parent ad62e1e677

commit 77e3d86f2f

1 changed files with 64 additions and 16 deletions

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drivers/acpi/cppc_acpi.c

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