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powerpc: powernv: Framework to show the correct clock in /proc/cpuinfo

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Currently, the code in setup-common.c for powerpc assumes that all
clock rates are same in a smp system. This value is cached in the
variable named ppc_proc_freq and is the value that is reported in
/proc/cpuinfo.

However on the PowerNV platform, the clock rate is same only across
the threads of the same core. Hence the value that is reported in
/proc/cpuinfo is incorrect on PowerNV platforms. We need a better way
to query and report the correct value of the processor clock in
/proc/cpuinfo.

The patch achieves this by creating a machdep_call named
get_proc_freq() which is expected to returns the frequency in Hz. The
code in show_cpuinfo() can invoke this method to display the correct
clock rate on platforms that have implemented this method. On the
other powerpc platforms it can use the value cached in ppc_proc_freq.

Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Gautham R. Shenoy 2014-03-11 17:01:18 +05:30 committed by Benjamin Herrenschmidt
parent 2196c6f1ed
commit 2299d03a63
2 changed files with 14 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/powerpc/include/asm/machdep.h
View File

@ -113,6 +113,8 @@ struct machdep_calls {
/* Optional, may be NULL. */
void (*show_cpuinfo)(struct seq_file *m);
void (*show_percpuinfo)(struct seq_file *m, int i);
/* Returns the current operating frequency of "cpu" in Hz */
unsigned long (*get_proc_freq)(unsigned int cpu);
void (*init_IRQ)(void);

16
arch/powerpc/kernel/setup-common.c
View File

@ -212,6 +212,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
{
unsigned long cpu_id = (unsigned long)v - 1;
unsigned int pvr;
unsigned long proc_freq;
unsigned short maj;
unsigned short min;
@ -263,12 +264,19 @@ static int show_cpuinfo(struct seq_file *m, void *v)
#endif /* CONFIG_TAU */
/*
* Assume here that all clock rates are the same in a
* smp system. -- Cort
* Platforms that have variable clock rates, should implement
* the method ppc_md.get_proc_freq() that reports the clock
* rate of a given cpu. The rest can use ppc_proc_freq to
* report the clock rate that is same across all cpus.
*/
if (ppc_proc_freq)
if (ppc_md.get_proc_freq)
proc_freq = ppc_md.get_proc_freq(cpu_id);
else
proc_freq = ppc_proc_freq;
if (proc_freq)
seq_printf(m, "clock\t\t: %lu.%06luMHz\n",
ppc_proc_freq / 1000000, ppc_proc_freq % 1000000);
proc_freq / 1000000, proc_freq % 1000000);
if (ppc_md.show_percpuinfo != NULL)
ppc_md.show_percpuinfo(m, cpu_id);