Commit Graph

8 Commits

Author SHA1 Message Date
Prakash, Prashanth
139aee73f0 ACPI / CPPC: check for error bit in PCC status field
PCC status field exposes an error bit(2) to indicate any errors during
the execution of last comamnd. This patch checks the error bit before
notifying success/failure to the cpufreq driver.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-08-31 01:02:34 +02:00
Ashwin Chaugule
158c998ea4 ACPI / CPPC: add sysfs support to compute delivered performance
The CPPC tables contain entries for per CPU feedback counters which
allows us to compute the delivered performance over a given interval
of time.

The math for delivered performance per the CPPCv5.0+ spec is:
  reference perf * delta(delivered perf ctr)/delta(ref perf ctr)

Maintaining deltas of the counters in the kernel is messy, as it
depends on when the reads are triggered. (e.g. via the cpufreq
->get() interface). Also the ->get() interace only returns one
value, so cant return raw values. So instead, leave it to userspace
to keep track of raw values and do its math for CPUs it cares about.

delivered and reference perf counters are exposed via the same
sysfs file to avoid the potential "skid", if these values are read
individually from userspace.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-08-31 01:02:34 +02:00
Prakash, Prashanth
be8b88d7d9 ACPI / CPPC: set a non-zero value for transition_latency
Compute the expected transition latency for frequency transitions
using the values from the PCCT tables when the desired perf
register is in PCC.

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Reviewed-by: Alexey Klimov <alexey.klimov@arm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-08-31 01:02:33 +02:00
Prakash, Prashanth
80b8286aee ACPI / CPPC: support for batching CPPC requests
CPPC defined in section 8.4.7 of ACPI 6.0 specification suggests
"To amortize the cost of PCC transactions, OSPM should read or write
all PCC registers via a single read or write command when possible"
This patch enables opportunistic batching of frequency transition
requests whenever the request happen to overlap in time.

Currently the access to pcc is serialized by a spin lock which does
not scale well as we increase the number of cores in the system. This
patch improves the scalability by allowing the differnt CPU cores to
update PCC subspace in parallel and by batching requests which will
reduce the certain types of operation(checking command completion bit,
ringing doorbell) by a significant margin.

Profiling shows significant improvement in the overall effeciency
to service freq. transition requests. With this patch we observe close
to 30% of the frequency transition requests being batched with other
requests while running apache bench on a ARM platform with 6
independent domains(or sets of related cpus).

Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-08-31 01:02:33 +02:00
Ashwin Chaugule
5bbb86aa4b ACPI / CPPC: restructure read/writes for efficient sys mapped reg ops
For cases where sys mapped CPC registers need to be accessed
frequently, it helps immensly to pre-map them rather than map
and unmap for each operation. e.g. case where feedback counters
are sys mem map registers.

Restructure cpc_read/write and the cpc_regs structure to allow
pre-mapping the system addresses and unmap them when the CPU exits.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-08-31 01:02:33 +02:00
Hoan Tran
866ae696e2 mailbox: pcc: Add PCC request and free channel declarations
Exports pcc_mbox_request_channel() and pcc_mbox_free_channel()
declarations into a pcc.h header file.

Looks-good-to: Prashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: Hoan Tran <hotran@apm.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-06-25 02:53:37 +02:00
Timur Tabi
2db8f9a1d8 ACPI / CPPC: remove redundant mbox_send_message() declaration
Remove a redundant function declaration in cppc_acpi.h for
mbox_send_message().  That function is defined in mailbox_client.h,
which is already included.

Signed-off-by: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2016-02-03 01:09:52 +01:00
Ashwin Chaugule
337aadff8e ACPI: Introduce CPU performance controls using CPPC
CPPC stands for Collaborative Processor Performance Controls
and is defined in the ACPI v5.0+ spec. It describes CPU
performance controls on an abstract and continuous scale
allowing the platform (e.g. remote power processor) to flexibly
optimize CPU performance with its knowledge of power budgets
and other architecture specific knowledge.

This patch adds a shim which exports commonly used functions
to get and set CPPC specific controls for each CPU. This enables
CPUFreq drivers to gather per CPU performance data and use
with exisiting governors or even allows for customized governors
which are implemented inside CPUFreq drivers.

Signed-off-by: Ashwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: Al Stone <al.stone@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
2015-10-12 22:49:55 +02:00