ANDROID: cpufreq: create dummy cpufreq driver

/proc/uid_time_in_state has no data on cuttlefish because its cpu
frequency tables are empty. Because time in state & concurrent time
accounting are intertwined this causes the
/proc/uid_concurrent_{policy,active}_time files to also not contain
any data.

Add a minimal, fake cpufreq driver that creates a freq table with 2
frequencies per policy, to allow testing time in state functionality.

Test: all 3 proc files show reasonable data on cuttlefish
Test: log shows no errors from bad /proc/uid_time_in_state format
Bug: 139763108
Bug: 140796321
Bug: 141206930
Change-Id: I8c7fe1007a80c21a9bcba9455bf837947cf42963
Signed-off-by: Connor O'Brien <connoro@google.com>

5 files changed, 66 insertions, 0 deletions

diff --git a/arch/arm64/configs/cuttlefish_defconfig b/arch/arm64/configs/cuttlefish_defconfig
index c17bac47626b..25196f10e922 100644
--- a/arch/arm64/configs/cuttlefish_defconfig
+++ b/arch/arm64/configs/cuttlefish_defconfig
@@ -66,6 +66,7 @@ CONFIG_CPU_FREQ_DEFAULT_GOV_SCHEDUTIL=y
 CONFIG_CPU_FREQ_GOV_POWERSAVE=y
 CONFIG_CPU_FREQ_GOV_CONSERVATIVE=y
 CONFIG_CPUFREQ_DT=y
+CONFIG_CPUFREQ_DUMMY=y
 CONFIG_ARM_BIG_LITTLE_CPUFREQ=y
 CONFIG_ARM_DT_BL_CPUFREQ=y
 CONFIG_NET=y
diff --git a/arch/x86/configs/x86_64_cuttlefish_defconfig b/arch/x86/configs/x86_64_cuttlefish_defconfig
index 826c660ae619..2c37d6864e8f 100644
--- a/arch/x86/configs/x86_64_cuttlefish_defconfig
+++ b/arch/x86/configs/x86_64_cuttlefish_defconfig
@@ -71,6 +71,7 @@ CONFIG_ACPI_PROCFS_POWER=y
 # CONFIG_X86_PM_TIMER is not set
 CONFIG_CPU_FREQ=y
 CONFIG_CPU_FREQ_GOV_ONDEMAND=y
+CONFIG_CPUFREQ_DUMMY=y
 CONFIG_X86_ACPI_CPUFREQ=y
 # CONFIG_X86_ACPI_CPUFREQ_CPB is not set
 CONFIG_PCI_MMCONFIG=y
diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 2a9ae9b71a1d..57e6cefcafed 100644
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -264,6 +264,15 @@ config CPUFREQ_DT
 
 	  If in doubt, say N.
 
+config CPUFREQ_DUMMY
+	tristate "Dummy CPU frequency driver"
+	help
+	  This option adds a generic dummy CPUfreq driver, which sets a fake
+	  2-frequency table when initializing each policy and otherwise does
+	  nothing.
+
+	  If in doubt, say N
+
 if X86
 source "drivers/cpufreq/Kconfig.x86"
 endif
diff --git a/drivers/cpufreq/Makefile b/drivers/cpufreq/Makefile
index 4575e1e24e24..c3cc00348c71 100644
--- a/drivers/cpufreq/Makefile
+++ b/drivers/cpufreq/Makefile
@@ -21,6 +21,8 @@ obj-$(CONFIG_CPU_FREQ_GOV_COMMON)		+= cpufreq_governor.o
 
 obj-$(CONFIG_CPUFREQ_DT)		+= cpufreq-dt.o
 
+obj-$(CONFIG_CPUFREQ_DUMMY)		+= dummy-cpufreq.o
+
 ##################################################################################
 # x86 drivers.
 # Link order matters. K8 is preferred to ACPI because of firmware bugs in early
diff --git a/drivers/cpufreq/dummy-cpufreq.c b/drivers/cpufreq/dummy-cpufreq.c
new file mode 100644
index 000000000000..203c859e2a7b
--- /dev/null
+++ b/drivers/cpufreq/dummy-cpufreq.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2019 Google, Inc.
+ */
+#include <linux/cpufreq.h>
+#include <linux/module.h>
+
+static struct cpufreq_frequency_table freq_table[] = {
+	{ .frequency = 1 },
+	{ .frequency = 2 },
+	{ .frequency = CPUFREQ_TABLE_END },
+};
+
+static int dummy_cpufreq_target_index(struct cpufreq_policy *policy,
+				   unsigned int index)
+{
+	return 0;
+}
+
+static int dummy_cpufreq_driver_init(struct cpufreq_policy *policy)
+{
+	return cpufreq_table_validate_and_show(policy, freq_table);
+}
+
+static int dummy_cpufreq_verify(struct cpufreq_policy *policy)
+{
+	return 0;
+}
+
+static struct cpufreq_driver dummy_cpufreq_driver = {
+	.name = "dummy",
+	.target_index = dummy_cpufreq_target_index,
+	.init = dummy_cpufreq_driver_init,
+	.verify = dummy_cpufreq_verify,
+	.attr = cpufreq_generic_attr,
+};
+
+static int __init dummy_cpufreq_init(void)
+{
+	return cpufreq_register_driver(&dummy_cpufreq_driver);
+}
+
+static void __exit dummy_cpufreq_exit(void)
+{
+	cpufreq_unregister_driver(&dummy_cpufreq_driver);
+}
+
+module_init(dummy_cpufreq_init);
+module_exit(dummy_cpufreq_exit);
+
+MODULE_AUTHOR("Connor O'Brien <connoro@google.com>");
+MODULE_DESCRIPTION("dummy cpufreq driver");
+MODULE_LICENSE("GPL");