diff options
author | Anshuman Khandual <khandual@linux.vnet.ibm.com> | 2015-05-21 12:13:04 +0530 |
---|---|---|
committer | Michael Ellerman <mpe@ellerman.id.au> | 2015-06-07 19:29:15 +1000 |
commit | d3cb06e0cdc9841b289a0d68acaffd2868504902 (patch) | |
tree | 3709e190a18c5c1c55fb609a1698ea291337a115 /arch | |
parent | 1db365258ad9c3624897f48c764f8c557f492b26 (diff) | |
download | linux-stable-d3cb06e0cdc9841b289a0d68acaffd2868504902.tar.gz linux-stable-d3cb06e0cdc9841b289a0d68acaffd2868504902.tar.bz2 linux-stable-d3cb06e0cdc9841b289a0d68acaffd2868504902.zip |
powerpc/dscr: Add some in-code documentation
This patch adds some in-code documentation to the DSCR related code to
make it more readable without having any functional change to it.
Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/powerpc/include/asm/processor.h | 9 | ||||
-rw-r--r-- | arch/powerpc/kernel/sysfs.c | 38 |
2 files changed, 47 insertions, 0 deletions
diff --git a/arch/powerpc/include/asm/processor.h b/arch/powerpc/include/asm/processor.h index bf117d8fb45f..28ded5d9b579 100644 --- a/arch/powerpc/include/asm/processor.h +++ b/arch/powerpc/include/asm/processor.h @@ -295,6 +295,15 @@ struct thread_struct { #endif #ifdef CONFIG_PPC64 unsigned long dscr; + /* + * This member element dscr_inherit indicates that the process + * has explicitly attempted and changed the DSCR register value + * for itself. Hence kernel wont use the default CPU DSCR value + * contained in the PACA structure anymore during process context + * switch. Once this variable is set, this behaviour will also be + * inherited to all the children of this process from that point + * onwards. + */ int dscr_inherit; unsigned long ppr; /* used to save/restore SMT priority */ #endif diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c index fa1fd8a0c867..692873bff334 100644 --- a/arch/powerpc/kernel/sysfs.c +++ b/arch/powerpc/kernel/sysfs.c @@ -496,13 +496,34 @@ static DEVICE_ATTR(spurr, 0400, show_spurr, NULL); static DEVICE_ATTR(purr, 0400, show_purr, store_purr); static DEVICE_ATTR(pir, 0400, show_pir, NULL); +/* + * This is the system wide DSCR register default value. Any + * change to this default value through the sysfs interface + * will update all per cpu DSCR default values across the + * system stored in their respective PACA structures. + */ static unsigned long dscr_default; +/** + * read_dscr() - Fetch the cpu specific DSCR default + * @val: Returned cpu specific DSCR default value + * + * This function returns the per cpu DSCR default value + * for any cpu which is contained in it's PACA structure. + */ static void read_dscr(void *val) { *(unsigned long *)val = get_paca()->dscr_default; } + +/** + * write_dscr() - Update the cpu specific DSCR default + * @val: New cpu specific DSCR default value to update + * + * This function updates the per cpu DSCR default value + * for any cpu which is contained in it's PACA structure. + */ static void write_dscr(void *val) { get_paca()->dscr_default = *(unsigned long *)val; @@ -520,12 +541,29 @@ static void add_write_permission_dev_attr(struct device_attribute *attr) attr->attr.mode |= 0200; } +/** + * show_dscr_default() - Fetch the system wide DSCR default + * @dev: Device structure + * @attr: Device attribute structure + * @buf: Interface buffer + * + * This function returns the system wide DSCR default value. + */ static ssize_t show_dscr_default(struct device *dev, struct device_attribute *attr, char *buf) { return sprintf(buf, "%lx\n", dscr_default); } +/** + * store_dscr_default() - Update the system wide DSCR default + * @dev: Device structure + * @attr: Device attribute structure + * @buf: Interface buffer + * @count: Size of the update + * + * This function updates the system wide DSCR default value. + */ static ssize_t __used store_dscr_default(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) |