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regulator: core: clamp voltage constraints before applying apply_uV

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machine_constraints_voltage() currently applies apply_uV against the
machine-supplied [min_uV, max_uV] range, and only afterwards clamps
that range down to what the regulator can actually supply (via
ops->list_voltage()).

If the machine-supplied range is wider than the regulator's actual
range, apply_uV's rounding can pick a selector outside the (correct)
clamped range, so the regulator ends up programmed outside its clamped
min/max. At bring-up this shows up as a voltage read-back outside the
clamped range.

Fix this by moving the clamping block ahead of the apply_uV block, so
apply_uV always targets an already-clamped range. Whether apply_uV
should run is decided from the unclamped constraints beforehand and
stored in a local bool, since clamping must not itself change whether
apply_uV fires.

No functional change to the clamping logic itself, only its position
relative to apply_uV. Its early return 0 exits become fallthroughs
since the apply_uV logic now follows it.

Assisted-by: Claude:claude-sonnet-5
Signed-off-by: Kamal Wadhwa <kamal.wadhwa@oss.qualcomm.com>
Link: https://patch.msgid.link/20260720-b4-regulator-core-clamp-voltage-v1-1-8e5eec076a8e@oss.qualcomm.com
Signed-off-by: Mark Brown <broonie@kernel.org>
This commit is contained in:
Kamal Wadhwa 2026-07-20 21:25:17 +05:30 committed by Mark Brown
parent 1d26f12550
commit a45cc646a3
No known key found for this signature in database
GPG Key ID: 24D68B725D5487D0
1 changed files with 90 additions and 73 deletions
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163
drivers/regulator/core.c
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@ -1220,10 +1220,98 @@ static int machine_constraints_voltage(struct regulator_dev *rdev,
{
const struct regulator_ops *ops = rdev->desc->ops;
int ret;
bool apply_uV;
/*
* Decide up front, from the constraints as handed to us, whether
* apply_uV needs to run below. The clamping pass right after this
* may rewrite constraints->min_uV/max_uV (e.g. the fixed-voltage
* autoconfigure case), and we don't want that to change whether
* apply_uV fires.
*/
apply_uV = rdev->constraints->apply_uV &&
rdev->constraints->min_uV && rdev->constraints->max_uV;
/*
* Constrain machine-level voltage specs to fit the actual range
* supported by this regulator before apply_uV (below) tries to
* force hardware to a value from that range: otherwise apply_uV
* can target a constraint value that doesn't correspond to any
* real voltage selector and fail registration outright, even
* though the clamping pass would have narrowed it to a value
* the regulator can actually hit.
*/
if (ops->list_voltage && rdev->desc->n_voltages) {
int count = rdev->desc->n_voltages;
int i;
int min_uV = INT_MAX;
int max_uV = INT_MIN;
int cmin = constraints->min_uV;
int cmax = constraints->max_uV;
/* it's safe to autoconfigure fixed-voltage supplies
* and the constraints are used by list_voltage.
*/
if (count == 1 && !cmin) {
cmin = 1;
cmax = INT_MAX;
constraints->min_uV = cmin;
constraints->max_uV = cmax;
}
/* voltage constraints are optional */
if ((cmin == 0) && (cmax == 0)) {
/* nothing more to do */
/* else require explicit machine-level constraints */
} else if (cmin <= 0 || cmax <= 0 || cmax < cmin) {
rdev_err(rdev, "invalid voltage constraints\n");
return -EINVAL;
/* no need to loop voltages if range is continuous */
} else if (rdev->desc->continuous_voltage_range) {
/* nothing more to do */
} else {
/* initial: [cmin..cmax] valid, [min_uV..max_uV] not */
for (i = 0; i < count; i++) {
int value;
value = ops->list_voltage(rdev, i);
if (value <= 0)
continue;
/* maybe adjust [min_uV..max_uV] */
if (value >= cmin && value < min_uV)
min_uV = value;
if (value <= cmax && value > max_uV)
max_uV = value;
}
/* final: [min_uV..max_uV] valid iff constraints valid */
if (max_uV < min_uV) {
rdev_err(rdev,
"unsupportable voltage constraints %u-%uuV\n",
min_uV, max_uV);
return -EINVAL;
}
/* use regulator's subset of machine constraints */
if (constraints->min_uV < min_uV) {
rdev_dbg(rdev, "override min_uV, %d -> %d\n",
constraints->min_uV, min_uV);
constraints->min_uV = min_uV;
}
if (constraints->max_uV > max_uV) {
rdev_dbg(rdev, "override max_uV, %d -> %d\n",
constraints->max_uV, max_uV);
constraints->max_uV = max_uV;
}
}
}
/* do we need to apply the constraint voltage */
if (rdev->constraints->apply_uV &&
rdev->constraints->min_uV && rdev->constraints->max_uV) {
if (apply_uV) {
int target_min, target_max;
int current_uV = regulator_get_voltage_rdev(rdev);
@ -1278,77 +1366,6 @@ static int machine_constraints_voltage(struct regulator_dev *rdev,
}
}
/* constrain machine-level voltage specs to fit
* the actual range supported by this regulator.
*/
if (ops->list_voltage && rdev->desc->n_voltages) {
int count = rdev->desc->n_voltages;
int i;
int min_uV = INT_MAX;
int max_uV = INT_MIN;
int cmin = constraints->min_uV;
int cmax = constraints->max_uV;
/* it's safe to autoconfigure fixed-voltage supplies
* and the constraints are used by list_voltage.
*/
if (count == 1 && !cmin) {
cmin = 1;
cmax = INT_MAX;
constraints->min_uV = cmin;
constraints->max_uV = cmax;
}
/* voltage constraints are optional */
if ((cmin == 0) && (cmax == 0))
return 0;
/* else require explicit machine-level constraints */
if (cmin <= 0 || cmax <= 0 || cmax < cmin) {
rdev_err(rdev, "invalid voltage constraints\n");
return -EINVAL;
}
/* no need to loop voltages if range is continuous */
if (rdev->desc->continuous_voltage_range)
return 0;
/* initial: [cmin..cmax] valid, [min_uV..max_uV] not */
for (i = 0; i < count; i++) {
int value;
value = ops->list_voltage(rdev, i);
if (value <= 0)
continue;
/* maybe adjust [min_uV..max_uV] */
if (value >= cmin && value < min_uV)
min_uV = value;
if (value <= cmax && value > max_uV)
max_uV = value;
}
/* final: [min_uV..max_uV] valid iff constraints valid */
if (max_uV < min_uV) {
rdev_err(rdev,
"unsupportable voltage constraints %u-%uuV\n",
min_uV, max_uV);
return -EINVAL;
}
/* use regulator's subset of machine constraints */
if (constraints->min_uV < min_uV) {
rdev_dbg(rdev, "override min_uV, %d -> %d\n",
constraints->min_uV, min_uV);
constraints->min_uV = min_uV;
}
if (constraints->max_uV > max_uV) {
rdev_dbg(rdev, "override max_uV, %d -> %d\n",
constraints->max_uV, max_uV);
constraints->max_uV = max_uV;
}
}
return 0;
}