applied to acpi test tree. thanks, -Len
>-----Original Message----- >From: Venkatesh Pallipadi [mailto:[EMAIL PROTECTED] >Sent: Friday, August 26, 2005 8:11 PM >To: Andrew Morton >Cc: linux-kernel; Brown, Len >Subject: [PATCH] acpi-cpufreq: Remove P-state read after a >P-state write in normal path > > > >Remove P-state read status after a P-state write in normal case. As >that operation is expensive. There are no known failures of a >set and we can >assume success in the common case. acpi_pstate_strict >parameter can be used >to force it back on any systems that is known to have errors. > >Signed-off-by: Venkatesh Pallipadi <[EMAIL PROTECTED]> > >Index: linux-2.6.12/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c >=================================================================== >--- >linux-2.6.12.orig/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c >2005-08-16 09:41:52.977456128 -0700 >+++ linux-2.6.12/arch/i386/kernel/cpu/cpufreq/acpi-cpufreq.c >2005-08-17 13:32:33.034651136 -0700 >@@ -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_driver acpi_cpufreq_driver; > >+static unsigned int acpi_pstate_strict; >+ > static int > acpi_processor_write_port( > u16 port, >@@ -163,34 +166,44 @@ > } > > /* >- * 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 @@ > 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); > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
