diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c | 57 |
1 files changed, 36 insertions, 21 deletions
diff --git a/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c b/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c index 60a9e54dd20..822c8ce9d1f 100644 --- a/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c +++ b/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c @@ -31,6 +31,7 @@ #include <linux/cpufreq.h> #include <linux/proc_fs.h> #include <linux/seq_file.h> +#include <linux/compiler.h> #include <asm/io.h> #include <asm/delay.h> #include <asm/uaccess.h> @@ -57,6 +58,8 @@ static struct cpufreq_acpi_io *acpi_io_data[NR_CPUS]; static struct cpufreq_driver acpi_cpufreq_driver; +static unsigned int acpi_pstate_strict; + static int acpi_processor_write_port( u16 port, @@ -163,34 +166,44 @@ acpi_processor_set_performance ( } /* - * Then we read the 'status_register' and compare the value with the - * target state's 'status' to make sure the transition was successful. - * Note that we'll poll for up to 1ms (100 cycles of 10us) before - * giving up. + * Assume the write went through when acpi_pstate_strict is not used. + * As read status_register is an expensive operation and there + * are no specific error cases where an IO port write will fail. */ - - port = data->acpi_data.status_register.address; - bit_width = data->acpi_data.status_register.bit_width; - - dprintk("Looking for 0x%08x from port 0x%04x\n", - (u32) data->acpi_data.states[state].status, port); - - for (i=0; i<100; i++) { - ret = acpi_processor_read_port(port, bit_width, &value); - if (ret) { - dprintk("Invalid port width 0x%04x\n", bit_width); - retval = ret; - goto migrate_end; + if (acpi_pstate_strict) { + /* Then we read the 'status_register' and compare the value + * with the target state's 'status' to make sure the + * transition was successful. + * Note that we'll poll for up to 1ms (100 cycles of 10us) + * before giving up. + */ + + port = data->acpi_data.status_register.address; + bit_width = data->acpi_data.status_register.bit_width; + + dprintk("Looking for 0x%08x from port 0x%04x\n", + (u32) data->acpi_data.states[state].status, port); + + for (i=0; i<100; i++) { + ret = acpi_processor_read_port(port, bit_width, &value); + if (ret) { + dprintk("Invalid port width 0x%04x\n", bit_width); + retval = ret; + goto migrate_end; + } + if (value == (u32) data->acpi_data.states[state].status) + break; + udelay(10); } - if (value == (u32) data->acpi_data.states[state].status) - break; - udelay(10); + } else { + i = 0; + value = (u32) data->acpi_data.states[state].status; } /* notify cpufreq */ cpufreq_notify_transition(&cpufreq_freqs, CPUFREQ_POSTCHANGE); - if (value != (u32) data->acpi_data.states[state].status) { + if (unlikely(value != (u32) data->acpi_data.states[state].status)) { unsigned int tmp = cpufreq_freqs.new; cpufreq_freqs.new = cpufreq_freqs.old; cpufreq_freqs.old = tmp; @@ -537,6 +550,8 @@ acpi_cpufreq_exit (void) return; } +module_param(acpi_pstate_strict, uint, 0644); +MODULE_PARM_DESC(acpi_pstate_strict, "value 0 or non-zero. non-zero -> strict ACPI checks are performed during frequency changes."); late_initcall(acpi_cpufreq_init); module_exit(acpi_cpufreq_exit); |