cpufreq: brcmstb-avs-cpufreq: add debugfs support

In order to aid debugging, we add a debugfs interface to the driver
that allows direct interaction with the AVS co-processor.

The debugfs interface provides a means for reading all and writing some
of the mailbox registers directly from the shell prompt and enables a
user to execute the communications protocol between ARM CPU and AVS CPU
step-by-step.

This interface should be used for debugging purposes only.

Signed-off-by: Markus Mayer <mmayer@broadcom.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/cpufreq/Kconfig.arm b/drivers/cpufreq/Kconfig.arm
index 04f7862eacd3..920c469f3953 100644
--- a/drivers/cpufreq/Kconfig.arm
+++ b/drivers/cpufreq/Kconfig.arm
@@ -23,6 +23,16 @@ config ARM_BRCMSTB_AVS_CPUFREQ
 
           Say Y, if you have a Broadcom SoC with AVS support for DFS or DVFS.
 
+config ARM_BRCMSTB_AVS_CPUFREQ_DEBUG
+        bool "Broadcom STB AVS CPUfreq driver sysfs debug capability"
+        depends on ARM_BRCMSTB_AVS_CPUFREQ
+        help
+          Enabling this option turns on debug support via sysfs under
+          /sys/kernel/debug/brcmstb-avs-cpufreq. It is possible to read all and
+          write some AVS mailbox registers through sysfs entries.
+
+          If in doubt, say N.
+
 config ARM_DT_BL_CPUFREQ
         tristate "Generic probing via DT for ARM big LITTLE CPUfreq driver"
         depends on ARM_BIG_LITTLE_CPUFREQ && OF