From bf5892a8167e4aa5a9a6d72f803fde850e0c5753 Mon Sep 17 00:00:00 2001 From: Mark Brown Date: Sun, 8 May 2011 22:13:37 +0100 Subject: [PATCH] regulator: Support voltage offsets to compensate for drops in system Some systems, particularly physically large systems used for early prototyping, may experience substantial voltage drops between the regulator and the consumers as a result of long traces in the system. With these systems voltages may need to be set higher than requested in order to ensure reliable system operation. Allow systems to work around such hardware issues by allowing constraints to supply an offset to be applied to any requested and reported voltages. This is not ideal, especially since the voltage drop may be load dependant, but is sufficient for most affected systems, it is not expected to be used in production hardware. The offset is applied after all constraint processing so constraints should be specified in terms of consumer values not physically configured values. Signed-off-by: Mark Brown Signed-off-by: Liam Girdwood --- drivers/regulator/core.c | 15 ++++++++++++--- include/linux/regulator/machine.h | 4 ++++ 2 files changed, 16 insertions(+), 3 deletions(-) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index 432faa5cb8af..58452ac0f165 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -724,6 +724,10 @@ static void print_constraints(struct regulator_dev *rdev) count += sprintf(buf + count, "at %d mV ", ret / 1000); } + if (constraints->uV_offset) + count += sprintf(buf, "%dmV offset ", + constraints->uV_offset / 1000); + if (constraints->min_uA && constraints->max_uA) { if (constraints->min_uA == constraints->max_uA) count += sprintf(buf + count, "%d mA ", @@ -1641,6 +1645,9 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev, trace_regulator_set_voltage(rdev_get_name(rdev), min_uV, max_uV); + min_uV += rdev->constraints->uV_offset; + max_uV += rdev->constraints->uV_offset; + if (rdev->desc->ops->set_voltage) { ret = rdev->desc->ops->set_voltage(rdev, min_uV, max_uV, &selector); @@ -1865,18 +1872,20 @@ EXPORT_SYMBOL_GPL(regulator_sync_voltage); static int _regulator_get_voltage(struct regulator_dev *rdev) { - int sel; + int sel, ret; if (rdev->desc->ops->get_voltage_sel) { sel = rdev->desc->ops->get_voltage_sel(rdev); if (sel < 0) return sel; - return rdev->desc->ops->list_voltage(rdev, sel); + ret = rdev->desc->ops->list_voltage(rdev, sel); } if (rdev->desc->ops->get_voltage) - return rdev->desc->ops->get_voltage(rdev); + ret = rdev->desc->ops->get_voltage(rdev); else return -EINVAL; + + return ret - rdev->constraints->uV_offset; } /** diff --git a/include/linux/regulator/machine.h b/include/linux/regulator/machine.h index 8f1a55d99494..ce3127a75c88 100644 --- a/include/linux/regulator/machine.h +++ b/include/linux/regulator/machine.h @@ -68,6 +68,8 @@ struct regulator_state { * * @min_uV: Smallest voltage consumers may set. * @max_uV: Largest voltage consumers may set. + * @uV_offset: Offset applied to voltages from consumer to compensate for + * voltage drops. * * @min_uA: Smallest consumers consumers may set. * @max_uA: Largest current consumers may set. @@ -99,6 +101,8 @@ struct regulation_constraints { int min_uV; int max_uV; + int uV_offset; + /* current output range (inclusive) - for current control */ int min_uA; int max_uA; -- 2.20.1