Newer versions of bimc-bwmon counters have the capability to fake
higher byte count than what's actually transferred between a bus
master and DDR if the bus master is being throttled by QoS hardware
logic. Add support to set the throttle adjust field that comes with
this newer version of bimc-bwmon.
Change-Id: I33376c825fb11ab2e378f828b1d2ae46dd582836
Signed-off-by: Rohit Gupta <rohgup@codeaurora.org>
The existing bw_hwmon governor samples the bandwidth every polling_interval
milliseconds and makes decisions. Polling interval of 50ms or even 10ms
gives a very low resolution picture of the DDR/bus traffic. Due to the
lower resolution picture, the existing governor algorithm has to be biased
aggressively towards performance to avoid any performance degradation
compared to using a static mapping between bus master (CPU, GPU, etc)
frequency to DDR/bus BW votes.
While the existing governor uses IRQ to get early notification of traffic
increase, even a 4x early notification for a 50ms polling interval still
takes 12.5ms. This kind of reaction time is still too slow for some bus
masters like CPU.
To take care of these limitations, rewrite the governor algorithm to take
multiple short samples of BW within a decision window (polling interval)
and use that higher resolution picture to make much better and faster
decisions. Doing so allows the governor to have the following features:
- Very low reaction time
- Over voting to stay ahead of increasing traffic
- Historic peak tracking to limit over voting
- Being power aware when doing over voting
- Pattern detection and intelligent hysteresis
- Detection low traffic modes and being less aggressive about BW votes
Change-Id: I69886b7fbeea0b64d10b5a1fb23fcb5f3918f0ce
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Some devfreq devices using this governor might need suspend/resume support.
When suspended, those devices won't need any bandwidth votes and there is
no point in monitoring their bandwidth either.
Therefore, upon suspend, vote for zero bandwidth and stop the HW monitor.
Upon resume, vote for the previous bandwidth and start the HW monitor.
Change-Id: I318449995d714959f0ebfe91961bc23fa8edbd04
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
The bandwidth monitoring devices might have more than one IRQ to handle or
might have notifications from other drivers instead of using actual IRQs.
So, refactor the governor to move the IRQ handling to the bandwidth
monitoring device specific drivers and just provide an API that can be used
to request a re-evaluation.
The device specific driver can call this API to request an immediate
re-evaluation whenever the bandwidth has exceeded the previously set limit
instead of waiting for the periodic update.
Change-Id: I8bfd85d0cb59a1fd0116000aac430680e483b422
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
The refactored governor will be called bw_hwmon since it's no longer
limited to monitoring the CPU BW in hardware.
The refactor allows the governor to support multiple devfreq devices. This
is done by having different HW monitor instances register their capability
to monitor different devfreq devices and then picking the right HW monitor
based on which devfreq device is using this governor.
The refactor also fixes a very unlikely race condition that can happen when
starting/stopping the governor.
Change-Id: Ifeeeb256115f6ae3075f391d9b4b02666e06f737
Signed-off-by: Saravana Kannan <skannan@codeaurora.org>
Rohit Gupta