From d511206dc7443120637efd9cfa3ab06a26da33dd Mon Sep 17 00:00:00 2001 From: Romain Gantois Date: Fri, 18 Jul 2025 16:11:36 +0200 Subject: [PATCH] regulator: core: repeat voltage setting request for stepped regulators The regulator_set_voltage() function may exhibit unexpected behavior if the target regulator has a maximum voltage step constraint. With such a constraint, the regulator core may clamp the requested voltage to a lesser value, to ensure that the voltage delta stays under the specified limit. This means that the resulting regulator voltage depends on the current voltage, as well as the requested range, which invalidates the assumption that a repeated request for a specific voltage range will amount to a noop. Considering the case of a regulator with a maximum voltage step constraint of 1V: initial voltage: 2.5V consumer requests 4V expected result: 3.5V resulting voltage: 3.5V consumer requests 4V again expected result: 4V actual result: 3.5V Correct this by repeating attempts to balance the regulator voltage until the result converges. Signed-off-by: Romain Gantois Link: https://patch.msgid.link/20250718-regulator-stepping-v2-1-e28c9ac5d54a@bootlin.com Signed-off-by: Mark Brown --- drivers/regulator/core.c | 43 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index cbd6d53ebfb5e..8ed9b96518cf5 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -3797,6 +3797,16 @@ static int _regulator_do_set_suspend_voltage(struct regulator_dev *rdev, return 0; } +static int regulator_get_voltage_delta(struct regulator_dev *rdev, int uV) +{ + int current_uV = regulator_get_voltage_rdev(rdev); + + if (current_uV < 0) + return current_uV; + + return abs(current_uV - uV); +} + static int regulator_set_voltage_unlocked(struct regulator *regulator, int min_uV, int max_uV, suspend_state_t state) @@ -3804,8 +3814,8 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator, struct regulator_dev *rdev = regulator->rdev; struct regulator_voltage *voltage = ®ulator->voltage[state]; int ret = 0; + int current_uV, delta, new_delta; int old_min_uV, old_max_uV; - int current_uV; /* If we're setting the same range as last time the change * should be a noop (some cpufreq implementations use the same @@ -3852,6 +3862,37 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator, voltage->max_uV = old_max_uV; } + if (rdev->constraints->max_uV_step > 0) { + /* For regulators with a maximum voltage step, reaching the desired + * voltage might take a few retries. + */ + ret = regulator_get_voltage_delta(rdev, min_uV); + if (ret < 0) + goto out; + + delta = ret; + + while (delta > 0) { + ret = regulator_balance_voltage(rdev, state); + if (ret < 0) + goto out; + + ret = regulator_get_voltage_delta(rdev, min_uV); + if (ret < 0) + goto out; + + new_delta = ret; + + /* check that voltage is converging quickly enough */ + if (new_delta - delta > rdev->constraints->max_uV_step) { + ret = -EWOULDBLOCK; + goto out; + } + + delta = new_delta; + } + } + out: return ret; } -- 2.47.2