We need to acquire pcc_lock only when we are accessing registers
that are in the PCC subspsace.
Signed-off-by: NPrashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NPrashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

When CPPC fails to request a PCC channel, the CPC data is freed
and cpc_desc_ptr points to the invalid data.

Avoid this issue by moving the cpc_desc_ptr assignment after the PCC
channel request.
Signed-off-by: NHoan Tran <hotran@apm.com>
Acked-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Based on 8.4.7.1 section of ACPI 6.1 specification, if the platform
supports CPPC, the _CPC object must exist under all processor objects.
If cpc_desc_ptr pointer is invalid on any CPUs, acpi_get_psd_map()
should return error and CPPC cpufreq driver can not be registered.
Signed-off-by: NHoan Tran <hotran@apm.com>
Reviewed-by: NPrashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The ACPI spec defines Minimum Request Turnaround Time(MRTT) and
Maximum Periodic Access Rate(MPAR) to prevent the OSPM from sending
too many requests than the platform can handle. For further details
on these parameters please refer to section 14.1.3 of ACPI 6.0 spec.

This patch includes MRTT/MPAR in deciding if or when a CPPC request
can be sent to the platform to make sure CPPC implementation is
compliant to the spec.
Signed-off-by: NPrashanth Prakash <pprakash@codeaurora.org>
Acked-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

We do not have a strict read/write order requirement while accessing
PCC subspace. The only requirement is all access should be committed
before triggering the PCC doorbell to transfer the ownership of PCC
to the platform and this requirement is enforced by the PCC driver.

Profiling on a many core system shows improvement of about 1.8us on
average per freq change request(about 10% improvement on average).
Since these operations are executed while holding the pcc_lock,
reducing this time helps the CPPC implementation to scale much
better as the number of cores increases.
Signed-off-by: NPrashanth Prakash <pprakash@codeaurora.org>
Acked-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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

Previously the send_pcc_cmd() code checked if the
PCC operation had completed before returning from
the function. This check was performed regardless
of the PCC op type (i.e. Read/Write). Knowing
the type of cmd can be used to optimize the check
and avoid needless waiting. e.g. with Write ops,
the actual Writing is done before calling send_pcc_cmd().
And the subsequent Writes will check if the channel is
free at the entry of send_pcc_cmd() anyway.

However, for Read cmds, we need to wait for the cmd
completion bit to be flipped, since the actual Read
ops follow after returning from the send_pcc_cmd(). So,
only do the looping check at the end for Read ops.

Also, instead of using udelay() calls, use ktime as a
means to check for deadlines. The current deadline
in which the Remote should flip the cmd completion bit
is defined as N * Nominal latency. Where N is arbitrary
and large enough to work on slow emulators and Nominal
latency comes from the ACPI table (PCCT). This helps
in working around the CONFIG_HZ effects on udelay()
and also avoids needing different ACPI tables for Silicon
and Emulation platforms.
Signed-off-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NPrashanth Prakash <pprakash@codeaurora.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

CPPC is enabled only on platforms which support the h/w reduced
ACPI specification, so use the h/w reduced version of the PCCT
consistently when deferencing PCCT contents.

Fixes: 337aadff (ACPI: Introduce CPU performance controls using CPPC)
Signed-off-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

Commit 337aadff (ACPI: Introduce CPU performance controls using CPPC)
leads to the following static checker warning:

        drivers/acpi/cppc_acpi.c:527 acpi_cppc_processor_probe()
        warn: overwrite may leak 'cpc_ptr'

Fix the warning by removing the bogus per-CPU pointer dereference.

Fixes: 337aadff (ACPI: Introduce CPU performance controls using CPPC)
Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

The "pcc_subspace_idx" is -1 if it hasn't been initialized yet.  We need
it to be signed.

Fixes: 337aadff (ACPI: Introduce CPU performance controls using CPPC)
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Acked-by: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

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: NAshwin Chaugule <ashwin.chaugule@linaro.org>
Reviewed-by: NAl Stone <al.stone@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>