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powerpc/dscr: Add some in-code documentation

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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>
This commit is contained in:
Anshuman Khandual 2015-05-21 12:13:04 +05:30 committed by Michael Ellerman
parent 1db365258a
commit d3cb06e0cd
2 changed files with 47 additions and 0 deletions
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9
arch/powerpc/include/asm/processor.h
View File

@ -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

38
arch/powerpc/kernel/sysfs.c
View File

@ -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)