diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/arm/memory.txt | 8 | ||||
| -rw-r--r-- | Documentation/arm/tcm.txt | 30 | ||||
| -rw-r--r-- | Documentation/credentials.txt | 3 | ||||
| -rw-r--r-- | Documentation/filesystems/xfs.txt | 11 |
4 files changed, 29 insertions, 23 deletions
diff --git a/Documentation/arm/memory.txt b/Documentation/arm/memory.txt index eb0fae18ffb1..771d48d3b335 100644 --- a/Documentation/arm/memory.txt +++ b/Documentation/arm/memory.txt @@ -33,7 +33,13 @@ ffff0000 ffff0fff CPU vector page. fffe0000 fffeffff XScale cache flush area. This is used in proc-xscale.S to flush the whole data - cache. Free for other usage on non-XScale. + cache. (XScale does not have TCM.) + +fffe8000 fffeffff DTCM mapping area for platforms with + DTCM mounted inside the CPU. + +fffe0000 fffe7fff ITCM mapping area for platforms with + ITCM mounted inside the CPU. fff00000 fffdffff Fixmap mapping region. Addresses provided by fix_to_virt() will be located here. diff --git a/Documentation/arm/tcm.txt b/Documentation/arm/tcm.txt index 77fd9376e6d7..7c15871c1885 100644 --- a/Documentation/arm/tcm.txt +++ b/Documentation/arm/tcm.txt @@ -19,8 +19,8 @@ defines a CPUID_TCM register that you can read out from the system control coprocessor. Documentation from ARM can be found at http://infocenter.arm.com, search for "TCM Status Register" to see documents for all CPUs. Reading this register you can -determine if ITCM (bit 0) and/or DTCM (bit 16) is present in the -machine. +determine if ITCM (bits 1-0) and/or DTCM (bit 17-16) is present +in the machine. There is further a TCM region register (search for "TCM Region Registers" at the ARM site) that can report and modify the location @@ -35,7 +35,15 @@ The TCM memory can then be remapped to another address again using the MMU, but notice that the TCM if often used in situations where the MMU is turned off. To avoid confusion the current Linux implementation will map the TCM 1 to 1 from physical to virtual -memory in the location specified by the machine. +memory in the location specified by the kernel. Currently Linux +will map ITCM to 0xfffe0000 and on, and DTCM to 0xfffe8000 and +on, supporting a maximum of 32KiB of ITCM and 32KiB of DTCM. + +Newer versions of the region registers also support dividing these +TCMs in two separate banks, so for example an 8KiB ITCM is divided +into two 4KiB banks with its own control registers. The idea is to +be able to lock and hide one of the banks for use by the secure +world (TrustZone). TCM is used for a few things: @@ -65,18 +73,18 @@ in <asm/tcm.h>. Using this interface it is possible to: memory. Such a heap is great for things like saving device state when shutting off device power domains. -A machine that has TCM memory shall select HAVE_TCM in -arch/arm/Kconfig for itself, and then the -rest of the functionality will depend on the physical -location and size of ITCM and DTCM to be defined in -mach/memory.h for the machine. Code that needs to use -TCM shall #include <asm/tcm.h> If the TCM is not located -at the place given in memory.h it will be moved using -the TCM Region registers. +A machine that has TCM memory shall select HAVE_TCM from +arch/arm/Kconfig for itself. Code that needs to use TCM shall +#include <asm/tcm.h> Functions to go into itcm can be tagged like this: int __tcmfunc foo(int bar); +Since these are marked to become long_calls and you may want +to have functions called locally inside the TCM without +wasting space, there is also the __tcmlocalfunc prefix that +will make the call relative. + Variables to go into dtcm can be tagged like this: int __tcmdata foo; diff --git a/Documentation/credentials.txt b/Documentation/credentials.txt index a2db35287003..995baf379c07 100644 --- a/Documentation/credentials.txt +++ b/Documentation/credentials.txt @@ -417,6 +417,9 @@ reference on them using: This does all the RCU magic inside of it. The caller must call put_cred() on the credentials so obtained when they're finished with. + [*] Note: The result of __task_cred() should not be passed directly to + get_cred() as this may race with commit_cred(). + There are a couple of convenience functions to access bits of another task's credentials, hiding the RCU magic from the caller: diff --git a/Documentation/filesystems/xfs.txt b/Documentation/filesystems/xfs.txt index 9878f50d6ed6..7bff3e4f35df 100644 --- a/Documentation/filesystems/xfs.txt +++ b/Documentation/filesystems/xfs.txt @@ -131,17 +131,6 @@ When mounting an XFS filesystem, the following options are accepted. Don't check for double mounted file systems using the file system uuid. This is useful to mount LVM snapshot volumes. - osyncisosync - Make O_SYNC writes implement true O_SYNC. WITHOUT this option, - Linux XFS behaves as if an "osyncisdsync" option is used, - which will make writes to files opened with the O_SYNC flag set - behave as if the O_DSYNC flag had been used instead. - This can result in better performance without compromising - data safety. - However if this option is not in effect, timestamp updates from - O_SYNC writes can be lost if the system crashes. - If timestamp updates are critical, use the osyncisosync option. - uquota/usrquota/uqnoenforce/quota User disk quota accounting enabled, and limits (optionally) enforced. Refer to xfs_quota(8) for further details. |