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@node Platform, Contributors, Maintenance, Top | |
@c %MENU% Describe all platform-specific facilities provided | |
@appendix Platform-specific facilities | |
@Theglibc{} can provide machine-specific functionality. | |
@menu | |
* PowerPC:: Facilities Specific to the PowerPC Architecture | |
@end menu | |
@node PowerPC | |
@appendixsec PowerPC-specific Facilities | |
Facilities specific to PowerPC that are not specific to a particular | |
operating system are declared in @file{sys/platform/ppc.h}. | |
@deftypefun {uint64_t} __ppc_get_timebase (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Read the current value of the Time Base Register. | |
The @dfn{Time Base Register} is a 64-bit register that stores a monotonically | |
incremented value updated at a system-dependent frequency that may be | |
different from the processor frequency. More information is available in | |
@cite{Power ISA 2.06b - Book II - Section 5.2}. | |
@code{__ppc_get_timebase} uses the processor's time base facility directly | |
without requiring assistance from the operating system, so it is very | |
efficient. | |
@end deftypefun | |
@deftypefun {uint64_t} __ppc_get_timebase_freq (void) | |
@safety{@prelim{}@mtunsafe{@mtuinit{}}@asunsafe{@asucorrupt{:init}}@acunsafe{@acucorrupt{:init}}} | |
@c __ppc_get_timebase_freq=__get_timebase_freq @mtuinit @acsfd | |
@c __get_clockfreq @mtuinit @asucorrupt:init @acucorrupt:init @acsfd | |
@c the initialization of the static timebase_freq is not exactly | |
@c safe, because hp_timing_t cannot be atomically set up. | |
@c syscall:get_tbfreq ok | |
@c open dup @acsfd | |
@c read dup ok | |
@c memcpy dup ok | |
@c memmem dup ok | |
@c close dup @acsfd | |
Read the current frequency at which the Time Base Register is updated. | |
This frequency is not related to the processor clock or the bus clock. | |
It is also possible that this frequency is not constant. More information is | |
available in @cite{Power ISA 2.06b - Book II - Section 5.2}. | |
@end deftypefun | |
The following functions provide hints about the usage of resources that are | |
shared with other processors. They can be used, for example, if a program | |
waiting on a lock intends to divert the shared resources to be used by other | |
processors. More information is available in @cite{Power ISA 2.06b - Book II - | |
Section 3.2}. | |
@deftypefun {void} __ppc_yield (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Provide a hint that performance will probably be improved if shared resources | |
dedicated to the executing processor are released for use by other processors. | |
@end deftypefun | |
@deftypefun {void} __ppc_mdoio (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Provide a hint that performance will probably be improved if shared resources | |
dedicated to the executing processor are released until all outstanding storage | |
accesses to caching-inhibited storage have been completed. | |
@end deftypefun | |
@deftypefun {void} __ppc_mdoom (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Provide a hint that performance will probably be improved if shared resources | |
dedicated to the executing processor are released until all outstanding storage | |
accesses to cacheable storage for which the data is not in the cache have been | |
completed. | |
@end deftypefun | |
@deftypefun {void} __ppc_set_ppr_med (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Set the Program Priority Register to medium value (default). | |
The @dfn{Program Priority Register} (PPR) is a 64-bit register that controls | |
the program's priority. By adjusting the PPR value the programmer may | |
improve system throughput by causing the system resources to be used | |
more efficiently, especially in contention situations. | |
The three unprivileged states available are covered by the functions | |
@code{__ppc_set_ppr_med} (medium -- default), @code{__ppc_set_ppc_low} (low) | |
and @code{__ppc_set_ppc_med_low} (medium low). More information | |
available in @cite{Power ISA 2.06b - Book II - Section 3.1}. | |
@end deftypefun | |
@deftypefun {void} __ppc_set_ppr_low (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Set the Program Priority Register to low value. | |
@end deftypefun | |
@deftypefun {void} __ppc_set_ppr_med_low (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Set the Program Priority Register to medium low value. | |
@end deftypefun | |
Power ISA 2.07 extends the priorities that can be set to the Program Priority | |
Register (PPR). The following functions implement the new priority levels: | |
very low and medium high. | |
@deftypefun {void} __ppc_set_ppr_very_low (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Set the Program Priority Register to very low value. | |
@end deftypefun | |
@deftypefun {void} __ppc_set_ppr_med_high (void) | |
@safety{@prelim{}@mtsafe{}@assafe{}@acsafe{}} | |
Set the Program Priority Register to medium high value. The medium high | |
priority is privileged and may only be set during certain time intervals by | |
problem-state programs. If the program priority is medium high when the time | |
interval expires or if an attempt is made to set the priority to medium high | |
when it is not allowed, the priority is set to medium. | |
@end deftypefun |