cpufreq: Add SFI based cpufreq driver support

This adds the SFI based cpu freq driver for some of the Intel's
Silvermont based Atom architectures like Z34xx and Z35xx.

Signed-off-by: Rudramuni, Vishwesh M <vishwesh.m.rudramuni@intel.com>
Signed-off-by: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Len Brown <len.brown@intel.com>

diff --git a/arch/x86/include/uapi/asm/msr-index.h b/arch/x86/include/uapi/asm/msr-index.h
index e21331ce368fc60a4ae7fd727448a4ca30d7bdf2..4f6dae67dd10587658bf43e4b0c4f806e02aad59 100644 (file)
--- a/arch/x86/include/uapi/asm/msr-index.h
+++ b/arch/x86/include/uapi/asm/msr-index.h
@@ -318,6 +318,7 @@
 
 #define MSR_IA32_PERF_STATUS           0x00000198
 #define MSR_IA32_PERF_CTL              0x00000199
+#define INTEL_PERF_CTL_MASK            0xffff
 #define MSR_AMD_PSTATE_DEF_BASE                0xc0010064
 #define MSR_AMD_PERF_STATUS            0xc0010063
 #define MSR_AMD_PERF_CTL               0xc0010062

diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index 89ae88f9189532d8313a5fee264de96393851cd0..c59bdcb83217071087cc0a90ef62e5cd01ce38d7 100644 (file)
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -57,6 +57,16 @@ config X86_ACPI_CPUFREQ_CPB
          By enabling this option the acpi_cpufreq driver provides the old
          entry in addition to the new boost ones, for compatibility reasons.
 
+config X86_SFI_CPUFREQ
+       tristate "SFI Performance-States driver"
+       depends on X86_INTEL_MID && SFI
+       help
+         This adds a CPUFreq driver for some Silvermont based Intel Atom
+         architectures like Z34xx and Z35xx which enumerate processor
+         performance states through SFI.
+
+         If in doubt, say N.
+
 config ELAN_CPUFREQ
        tristate "AMD Elan SC400 and SC410"
        depends on MELAN

diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 40c53dc1937ec6a4fc22e61f497939ba2ada54bd..2e50f55e14d3a3bb2303480677d3043087c2f9af 100644 (file)
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -41,6 +41,7 @@ obj-$(CONFIG_X86_P4_CLOCKMOD)         += p4-clockmod.o
 obj-$(CONFIG_X86_CPUFREQ_NFORCE2)      += cpufreq-nforce2.o
 obj-$(CONFIG_X86_INTEL_PSTATE)         += intel_pstate.o
 obj-$(CONFIG_X86_AMD_FREQ_SENSITIVITY) += amd_freq_sensitivity.o
+obj-$(CONFIG_X86_SFI_CPUFREQ)          += sfi-cpufreq.o
 
 ##################################################################################
 # ARM SoC drivers

diff --git a/drivers/cpufreq/sfi-cpufreq.c b/drivers/cpufreq/sfi-cpufreq.c
new file mode 100644 (file)
index 0000000..ffa3389
--- /dev/null
+++ b/drivers/cpufreq/sfi-cpufreq.c
@@ -0,0 +1,136 @@
+/*
+ *  SFI Performance States Driver
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  Author: Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>
+ *  Author: Srinidhi Kasagar <srinidhi.kasagar@intel.com>
+ */
+
+#include <linux/cpufreq.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sfi.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+
+#include <asm/msr.h>
+
+struct cpufreq_frequency_table *freq_table;
+static struct sfi_freq_table_entry *sfi_cpufreq_array;
+static int num_freq_table_entries;
+
+static int sfi_parse_freq(struct sfi_table_header *table)
+{
+       struct sfi_table_simple *sb;
+       struct sfi_freq_table_entry *pentry;
+       int totallen;
+
+       sb = (struct sfi_table_simple *)table;
+       num_freq_table_entries = SFI_GET_NUM_ENTRIES(sb,
+                       struct sfi_freq_table_entry);
+       if (num_freq_table_entries <= 1) {
+               pr_err("No p-states discovered\n");
+               return -ENODEV;
+       }
+
+       pentry = (struct sfi_freq_table_entry *)sb->pentry;
+       totallen = num_freq_table_entries * sizeof(*pentry);
+
+       sfi_cpufreq_array = kzalloc(totallen, GFP_KERNEL);
+       if (!sfi_cpufreq_array)
+               return -ENOMEM;
+
+       memcpy(sfi_cpufreq_array, pentry, totallen);
+
+       return 0;
+}
+
+static int sfi_cpufreq_target(struct cpufreq_policy *policy, unsigned int index)
+{
+       unsigned int next_perf_state = 0; /* Index into perf table */
+       u32 lo, hi;
+
+       next_perf_state = policy->freq_table[index].driver_data;
+
+       rdmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, &lo, &hi);
+       lo = (lo & ~INTEL_PERF_CTL_MASK) |
+               ((u32) sfi_cpufreq_array[next_perf_state].ctrl_val &
+               INTEL_PERF_CTL_MASK);
+       wrmsr_on_cpu(policy->cpu, MSR_IA32_PERF_CTL, lo, hi);
+
+       return 0;
+}
+
+static int sfi_cpufreq_cpu_init(struct cpufreq_policy *policy)
+{
+       policy->shared_type = CPUFREQ_SHARED_TYPE_HW;
+       policy->cpuinfo.transition_latency = 100000;    /* 100us */
+
+       return cpufreq_table_validate_and_show(policy, freq_table);
+}
+
+static struct cpufreq_driver sfi_cpufreq_driver = {
+       .flags          = CPUFREQ_CONST_LOOPS,
+       .verify         = cpufreq_generic_frequency_table_verify,
+       .target_index   = sfi_cpufreq_target,
+       .init           = sfi_cpufreq_cpu_init,
+       .name           = "sfi-cpufreq",
+       .attr           = cpufreq_generic_attr,
+};
+
+static int __init sfi_cpufreq_init(void)
+{
+       int ret, i;
+
+       /* parse the freq table from SFI */
+       ret = sfi_table_parse(SFI_SIG_FREQ, NULL, NULL, sfi_parse_freq);
+       if (ret)
+               return ret;
+
+       freq_table = kzalloc(sizeof(*freq_table) *
+                       (num_freq_table_entries + 1), GFP_KERNEL);
+       if (!freq_table) {
+               ret = -ENOMEM;
+               goto err_free_array;
+       }
+
+       for (i = 0; i < num_freq_table_entries; i++) {
+               freq_table[i].driver_data = i;
+               freq_table[i].frequency = sfi_cpufreq_array[i].freq_mhz * 1000;
+       }
+       freq_table[i].frequency = CPUFREQ_TABLE_END;
+
+       ret = cpufreq_register_driver(&sfi_cpufreq_driver);
+       if (ret)
+               goto err_free_tbl;
+
+       return ret;
+
+err_free_tbl:
+       kfree(freq_table);
+err_free_array:
+       kfree(sfi_cpufreq_array);
+       return ret;
+}
+late_initcall(sfi_cpufreq_init);
+
+static void __exit sfi_cpufreq_exit(void)
+{
+       cpufreq_unregister_driver(&sfi_cpufreq_driver);
+       kfree(freq_table);
+       kfree(sfi_cpufreq_array);
+}
+module_exit(sfi_cpufreq_exit);
+
+MODULE_AUTHOR("Vishwesh M Rudramuni <vishwesh.m.rudramuni@intel.com>");
+MODULE_DESCRIPTION("SFI Performance-States Driver");
+MODULE_LICENSE("GPL");