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@ -15,8 +15,9 @@ Contents :
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10. [Firmware Image Package (FIP)](#10--firmware-image-package-fip)
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11. [Use of coherent memory in Trusted Firmware](#11--use-of-coherent-memory-in-trusted-firmware)
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12. [Isolating code and read-only data on separate memory pages](#12--isolating-code-and-read-only-data-on-separate-memory-pages)
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13. [Code Structure](#13--code-structure)
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14. [References](#14--references)
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13. [Performance Measurement Framework](#13--performance-measurement-framework)
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14. [Code Structure](#14--code-structure)
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15. [References](#15--references)
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1. Introduction
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@ -2016,7 +2017,128 @@ This build flag is disabled by default, minimising memory footprint. On ARM
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platforms, it is enabled.
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13. Code Structure
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13. Performance Measurement Framework
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--------------------------------------
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The Performance Measurement Framework (PMF) facilitates collection of
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timestamps by registered services and provides interfaces to retrieve
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them from within the ARM Trusted Firmware. A platform can choose to
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expose appropriate SMCs to retrieve these collected timestamps.
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By default, the global physical counter is used for the timestamp
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value and is read via `CNTPCT_EL0`. The framework allows to retrieve
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timestamps captured by other CPUs.
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### Timestamp identifier format
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A PMF timestamp is uniquely identified across the system via the
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timestamp ID or `tid`. The `tid` is composed as follows:
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Bits 0-7: The local timestamp identifier.
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Bits 8-9: Reserved.
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Bits 10-15: The service identifier.
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Bits 16-31: Reserved.
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1. The service identifier. Each PMF service is identified by a
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service name and a service identifier. Both the service name and
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identifier are unique within the system as a whole.
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2. The local timestamp identifier. This identifier is unique within a given
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service.
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### Registering a PMF service
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To register a PMF service, the `PMF_REGISTER_SERVICE()` macro from `pmf.h`
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is used. The arguments required are the service name, the service ID,
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the total number of local timestamps to be captured and a set of flags.
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The `flags` field can be specified as a bitwise-OR of the following values:
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PMF_STORE_ENABLE: The timestamp is stored in memory for later retrieval.
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PMF_DUMP_ENABLE: The timestamp is dumped on the serial console.
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The `PMF_REGISTER_SERVICE()` reserves memory to store captured
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timestamps in a PMF specific linker section at build time.
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Additionally, it defines necessary functions to capture and
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retrieve a particular timestamp for the given service at runtime.
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The macro `PMF_REGISTER_SERVICE()` only enables capturing PMF
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timestamps from within ARM Trusted Firmware. In order to retrieve
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timestamps from outside of ARM Trusted Firmware, the
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`PMF_REGISTER_SERVICE_SMC()` macro must be used instead. This macro
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accepts the same set of arguments as the `PMF_REGISTER_SERVICE()`
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macro but additionally supports retrieving timestamps using SMCs.
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### Capturing a timestamp
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PMF timestamps are stored in a per-service timestamp region. On a
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system with multiple CPUs, each timestamp is captured and stored
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in a per-CPU cache line aligned memory region.
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Having registered the service, the `PMF_CAPTURE_TIMESTAMP()` macro can be
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used to capture a timestamp at the location where it is used. The macro
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takes the service name, a local timestamp identifier and a flag as arguments.
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The `flags` field argument can be zero, or `PMF_CACHE_MAINT` which
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instructs PMF to do cache maintenance following the capture. Cache
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maintenance is required if any of the service's timestamps are captured
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with data cache disabled.
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To capture a timestamp in assembly code, the caller should use
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`pmf_calc_timestamp_addr` macro (defined in `pmf_asm_macros.S`) to
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calculate the address of where the timestamp would be stored. The
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caller should then read `CNTPCT_EL0` register to obtain the timestamp
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and store it at the determined address for later retrieval.
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### Retrieving a timestamp
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From within ARM Trusted Firmware, timestamps for individual CPUs can
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be retrieved using either `PMF_GET_TIMESTAMP_BY_MPIDR()` or
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`PMF_GET_TIMESTAMP_BY_INDEX()` macros. These macros accept the CPU's MPIDR
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value, or its ordinal position, respectively.
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From outside ARM Trusted Firmware, timestamps for individual CPUs can be
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retrieved by calling into `pmf_smc_handler()`.
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Interface : pmf_smc_handler()
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Argument : unsigned int smc_fid, u_register_t x1,
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u_register_t x2, u_register_t x3,
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u_register_t x4, void *cookie,
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void *handle, u_register_t flags
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Return : uintptr_t
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smc_fid: Holds the SMC identifier which is either `PMF_SMC_GET_TIMESTAMP_32`
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when the caller of the SMC is running in AArch32 mode
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or `PMF_SMC_GET_TIMESTAMP_64` when the caller is running in AArch64 mode.
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x1: Timestamp identifier.
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x2: The `mpidr` of the CPU for which the timestamp has to be retrieved.
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This can be the `mpidr` of a different core to the one initiating
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the SMC. In that case, service specific cache maintenance may be
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required to ensure the updated copy of the timestamp is returned.
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x3: A flags value that is either 0 or `PMF_CACHE_MAINT`. If
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`PMF_CACHE_MAINT` is passed, then the PMF code will perform a
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cache invalidate before reading the timestamp. This ensures
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an updated copy is returned.
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The remaining arguments, `x4`, `cookie`, `handle` and `flags` are unused
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in this implementation.
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### PMF code structure
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1. `pmf_main.c` consists of core functions that implement service registration,
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initialization, storing, dumping and retrieving timestamps.
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2. `pmf_smc.c` contains the SMC handling for registered PMF services.
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3. `pmf.h` contains the public interface to Performance Measurement Framework.
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4. `pmf_asm_macros.S` consists of macros to facilitate capturing timestamps in
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assembly code.
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5. `pmf_helpers.h` is an internal header used by `pmf.h`.
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14. Code Structure
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-------------------
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Trusted Firmware code is logically divided between the three boot loader
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@ -2060,7 +2182,7 @@ FDTs provide a description of the hardware platform and are used by the Linux
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kernel at boot time. These can be found in the `fdts` directory.
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14. References
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15. References
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---------------
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1. Trusted Board Boot Requirements CLIENT PDD (ARM DEN 0006B-5). Available
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