[RFC PATCH 0/2] cpufreq/regulator: Limit minimum voltage only

[Taras Kondratiuk]

Using a "voltage tolerance" for doing DVFS is not a proper way.
It leads to a few issues:
- voltage is limited to a narrow range near OPP voltage,
  so other consumers of the same regulator can't set their own constraints
  if they don't overlap with this narrow range. No ganged rails :(
- usually OPP voltage is an absolute minimum voltage
  necessary for correct work (not taking into account AVS).
  Applying plus/minus tolerance can lead to an unstable device.
  For example omap-cpufreq has 4% tolerance configured,
  so for OMAP4430 MPU OPP50 we get 0.984V instead of 1.025V. 

This series adds a new API to regulator FW to limit only minimum voltage.
As example API is used for cpufreq-cpu0, but if it is accepted I'll fix
other drivers (omap-cpufreq, imx6q-cpufreq, etc).
Maybe regulator_set_voltage_tol() should be removed completely,
because it started to be used in a wrong way.
  
Patches are based on v3.9-rc7.
I've tested them on v3.8 based branch on OMAP4430 Blaze board.

Taras Kondratiuk (2):
  regulator: core: Add regulator_set_voltage_min()
  cpufreq: cpufreq-cpu0: Limit minimum voltage only

 drivers/cpufreq/cpufreq-cpu0.c     |   12 ++++--------
 include/linux/regulator/consumer.h |    6 ++++++
 2 files changed, 10 insertions(+), 8 deletions(-)

-- 
1.7.9.5

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