aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation/x86/intel_mid/intel_mid_ocd.txt
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/x86/intel_mid/intel_mid_ocd.txt')
-rw-r--r--Documentation/x86/intel_mid/intel_mid_ocd.txt86
1 files changed, 86 insertions, 0 deletions
diff --git a/Documentation/x86/intel_mid/intel_mid_ocd.txt b/Documentation/x86/intel_mid/intel_mid_ocd.txt
new file mode 100644
index 00000000000..d9483b0b6af
--- /dev/null
+++ b/Documentation/x86/intel_mid/intel_mid_ocd.txt
@@ -0,0 +1,86 @@
+Kernel driver over current detection driver
+===========================================
+
+Supported systems:
+ * Intel Medfield Platform
+
+Author: Durgadoss R
+
+Description
+-----------
+
+This driver monitors the current drawn by the platform, and detects the
+peak current conditions. When the current drawn is more than the
+configured limit for a period of time (which is specified by a timer), an
+interrupt is generated. The current limit and the timer value can be
+configured at run time.
+
+The current thresholds aka BATTCURRENTLIMITS(BC) are of two types:
+ 1.warning threshold(BC1)
+ at which the system should take actions to bring the
+ current consumption down.
+ 2.shutdown threshold(BC2)
+ at which the hardware does a COLDOFF.
+
+The timer thresholds are of three types:
+ 1.warning threshold(T1)
+ This corresponds to the first flag for time that the battery
+ current has been above BC1. An interrupt is generated to allow
+ software to correct the situation based on use-case.
+ 2.hardware action threshold(T2)
+ This corresponds to the second flag for time that the battery
+ current has been above BC1. It signifies that the system
+ should control high current subsystems through hardware.
+ Besides a general interrupt, audio_volume_crush, vibra_disable
+ signals are sent.
+ 3.shutdown threshold(T3)
+ This final flag signifies that when the system current exceeds
+ the threshold for more than T3, system should shutdown.
+
+Following table summarizes the exported sysfs files:
+
+bcu_status(RW) - To enable/disable burst control unit.
+ 0 - enables bcu, 1 - disables bcu.
+accumulation_time(RW)- Time since last clearing/overflow of warning_count
+ in milli seconds. Writing 0 resets the acc_time and
+ also clears both the warning counters.
+warning_count(RO) - Two space seperated values that indicate the number
+ of times the current thresholds have been crossed.
+action_mask(RW) - A hex value to enable/disable specific
+ actions taken when current violation happens.
+ bits [b4 b3 b2 b1 b0] control [a4 a3 a2 a1 a0] actions
+ respectively. a4 - camera output, a3 - sys burst,
+ a2 - SOC burst enable, a1 - vibra, a0 - audio output.
+ bits [b7 b6 b5] - Reserved.
+ Default value:08 (sys burst output is enabled).
+action_status(RO) - A hex value showing the status of actions taken
+ since the __last__ interrupt.
+ b7 - T3 violation
+ b6 - T2 violation
+ b5 - T1 violation
+ b4 - camera action taken status
+ b3 - sys burst disable action taken status
+ b2 - SOC burst disable action taken status
+ b1 - vibra disable
+ b0 - audio volume crush
+ A '1' in a bit position indicates that particular
+ action has been taken.
+current_warning(RW) - This gives the current(in mA) at which a warning is
+ generated. Range: 1400 to 4800. Default:3000
+current_shutdown(RW) - This gives the current(in mA) at which system shutdown
+ is initiated. Range:1800 to 5800. Default:3800
+timer_warning(RW) - Time above current_warning limit at which interrupts
+ are trigerred(so that software can bring the current
+ consumption down). Values are in micro seconds.
+ Range:200 to 7700 in steps of 500
+timer_hw_action(RW) - Time above current_warning limit at which the system
+ is trigerred into hardware control to bring down the
+ current consumption. Values are in micro seconds.
+ Range:200 to 7700 in steps of 500
+timer_shutdown(RW) - Time above current_warning limit at which a hardware
+ shutdown event is trigerred. The timer values are in
+ micro seconds.
+ Range:1000 to 15000 in steps of 1000
+For all timer interfaces, tolerance shall be 5% maximum.
+All timers start running concurrently once current_warning/current_shutdown
+is crossed.