regulator: core: correct convergence check in regulator_set_voltage()

The logic in regulator_set_voltage() which checks for a non-convergence
condition on a stepped regulator is flawed.

regulator_set_voltage() checks if the error in target voltage has increased
or decreased, and returns -EWOULDBLOCK if the error has not decreased
enough. The correct non-convergence condition is:

new_delta - delta > -rdev->constraints->max_uV_step

or equivalently:

delta - new_delta < rdev->constraints->max_uV_step

But the currently used condition is:

new_delta - delta > rdev->constraints->max_uV_step

Which may cause an infinite loop if the voltage error doesn't converge.

Fix this by correcting the convergence condition.

Suggested-by: Jon Hunter <jonathanh@nvidia.com>
Fixes: d511206dc7443 ("regulator: core: repeat voltage setting request for stepped regulators")
Signed-off-by: Romain Gantois <romain.gantois@bootlin.com>
Link: https://patch.msgid.link/20250729-b4-regulator-stepping-fix-v1-1-3f7b8c55d7d7@bootlin.com
Tested-by: Jon Hunter <jonathanh@nvidia.com>
Reviewed-by: Jon Hunter <jonathanh@nvidia.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 8ed9b96518cf5186c0db147a6895a92bc59fae4e..554d83c4af0c1c98edb43b60dbfacb8844d5e1eb 100644 (file)
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -3884,7 +3884,7 @@ static int regulator_set_voltage_unlocked(struct regulator *regulator,
                        new_delta = ret;
 
                        /* check that voltage is converging quickly enough */
-                       if (new_delta - delta > rdev->constraints->max_uV_step) {
+                       if (delta - new_delta < rdev->constraints->max_uV_step) {
                                ret = -EWOULDBLOCK;
                                goto out;
                        }