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82 lines
3.3 KiB
Plaintext
82 lines
3.3 KiB
Plaintext
@node Platform, Contributors, Maintenance, Top
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@c %MENU% Describe all platform-specific facilities provided
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@appendix Platform-specific facilities
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@Theglibc{} can provide machine-specific functionality.
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@menu
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* PowerPC:: Facilities Specific to the PowerPC Architecture
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@end menu
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@node PowerPC
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@appendixsec PowerPC-specific Facilities
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Facilities specific to PowerPC that are not specific to a particular
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operating system are declared in @file{sys/platform/ppc.h}.
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@deftypefun {uint64_t} __ppc_get_timebase (void)
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Read the current value of the Time Base Register.
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The @dfn{Time Base Register} is a 64-bit register that stores a monotonically
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incremented value updated at a system-dependent frequency that may be
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different from the processor frequency. More information is available in
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@cite{Power ISA 2.06b - Book II - Section 5.2}.
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@code{__ppc_get_timebase} uses the processor's time base facility directly
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without requiring assistance from the operating system, so it is very
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efficient.
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@end deftypefun
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@deftypefun {uint64_t} __ppc_get_timebase_freq (void)
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Read the current frequency at which the Time Base Register is updated.
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This frequency is not related to the processor clock or the bus clock.
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It is also possible that this frequency is not constant. More information is
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available in @cite{Power ISA 2.06b - Book II - Section 5.2}.
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@end deftypefun
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The following functions provide hints about the usage of resources that are
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shared with other processors. They can be used, for example, if a program
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waiting on a lock intends to divert the shared resources to be used by other
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processors. More information is available in @cite{Power ISA 2.06b - Book II -
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Section 3.2}.
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@deftypefun {void} __ppc_yield (void)
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Provide a hint that performance will probably be improved if shared resources
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dedicated to the executing processor are released for use by other processors.
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@end deftypefun
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@deftypefun {void} __ppc_mdoio (void)
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Provide a hint that performance will probably be improved if shared resources
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dedicated to the executing processor are released until all outstanding storage
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accesses to caching-inhibited storage have been completed.
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@end deftypefun
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@deftypefun {void} __ppc_mdoom (void)
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Provide a hint that performance will probably be improved if shared resources
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dedicated to the executing processor are released until all outstanding storage
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accesses to cacheable storage for which the data is not in the cache have been
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completed.
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@end deftypefun
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@deftypefun {void} __ppc_set_ppr_med (void)
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Set the Program Priority Register to medium value (default).
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The @dfn{Program Priority Register} (PPR) is a 64-bit register that controls
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the program's priority. By adjusting the PPR value the programmer may
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improve system throughput by causing the system resources to be used
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more efficiently, especially in contention situations.
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The three unprivileged states available are covered by the functions
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@code{__ppc_set_ppr_med} (medium -- default), @code{__ppc_set_ppc_low} (low)
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and @code{__ppc_set_ppc_med_low} (medium low). More information
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available in @cite{Power ISA 2.06b - Book II - Section 3.1}.
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@end deftypefun
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@deftypefun {void} __ppc_set_ppr_low (void)
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Set the Program Priority Register to low value.
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@end deftypefun
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@deftypefun {void} __ppc_set_ppr_med_low (void)
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Set the Program Priority Register to medium low value.
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@end deftypefun
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