diff options
Diffstat (limited to 'Documentation/arm')
| -rw-r--r-- | Documentation/arm/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/arm/OMAP/omap_pm | 25 | ||||
| -rw-r--r-- | Documentation/arm/swp_emulation | 27 |
3 files changed, 54 insertions, 0 deletions
diff --git a/Documentation/arm/00-INDEX b/Documentation/arm/00-INDEX index ecf7d04bca26..91c24a1e8a9e 100644 --- a/Documentation/arm/00-INDEX +++ b/Documentation/arm/00-INDEX @@ -34,3 +34,5 @@ memory.txt - description of the virtual memory layout nwfpe/ - NWFPE floating point emulator documentation +swp_emulation + - SWP/SWPB emulation handler/logging description diff --git a/Documentation/arm/OMAP/omap_pm b/Documentation/arm/OMAP/omap_pm index 5389440aade3..9012bb039094 100644 --- a/Documentation/arm/OMAP/omap_pm +++ b/Documentation/arm/OMAP/omap_pm @@ -127,3 +127,28 @@ implementation needs: 10. (*pdata->cpu_set_freq)(unsigned long f) 11. (*pdata->cpu_get_freq)(void) + +Customizing OPP for platform +============================ +Defining CONFIG_PM should enable OPP layer for the silicon +and the registration of OPP table should take place automatically. +However, in special cases, the default OPP table may need to be +tweaked, for e.g.: + * enable default OPPs which are disabled by default, but which + could be enabled on a platform + * Disable an unsupported OPP on the platform + * Define and add a custom opp table entry +in these cases, the board file needs to do additional steps as follows: +arch/arm/mach-omapx/board-xyz.c + #include "pm.h" + .... + static void __init omap_xyz_init_irq(void) + { + .... + /* Initialize the default table */ + omapx_opp_init(); + /* Do customization to the defaults */ + .... + } +NOTE: omapx_opp_init will be omap3_opp_init or as required +based on the omap family. diff --git a/Documentation/arm/swp_emulation b/Documentation/arm/swp_emulation new file mode 100644 index 000000000000..af903d22fd93 --- /dev/null +++ b/Documentation/arm/swp_emulation @@ -0,0 +1,27 @@ +Software emulation of deprecated SWP instruction (CONFIG_SWP_EMULATE) +--------------------------------------------------------------------- + +ARMv6 architecture deprecates use of the SWP/SWPB instructions, and recommeds +moving to the load-locked/store-conditional instructions LDREX and STREX. + +ARMv7 multiprocessing extensions introduce the ability to disable these +instructions, triggering an undefined instruction exception when executed. +Trapped instructions are emulated using an LDREX/STREX or LDREXB/STREXB +sequence. If a memory access fault (an abort) occurs, a segmentation fault is +signalled to the triggering process. + +/proc/cpu/swp_emulation holds some statistics/information, including the PID of +the last process to trigger the emulation to be invocated. For example: +--- +Emulated SWP: 12 +Emulated SWPB: 0 +Aborted SWP{B}: 1 +Last process: 314 +--- + +NOTE: when accessing uncached shared regions, LDREX/STREX rely on an external +transaction monitoring block called a global monitor to maintain update +atomicity. If your system does not implement a global monitor, this option can +cause programs that perform SWP operations to uncached memory to deadlock, as +the STREX operation will always fail. + |