On 25.08.2022 23:28, Christian Kohlschütter wrote:
> Previously, an unresolved regulator supply reference upon calling
> regulator_register on an always-on or boot-on regulator caused
> set_machine_constraints to be called twice.
>
> This in turn may initialize the regulator twice, leading to voltage
> glitches that are timing-dependent. A simple, unrelated configuration
> change may be enough to hide this problem, only to be surfaced by
> chance.
>
> One such example is the SD-Card voltage regulator in a NanoPI R4S that
> would not initialize reliably unless the registration flow was just
> complex enough to allow the regulator to properly reset between calls.
>
> Fix this by re-arranging regulator_register, trying resolve the
> regulator's supply early enough that set_machine_constraints does not
> need to be called twice.
>
> Signed-off-by: Christian Kohlschütter <christian@xxxxxxxxxxxxxxxx>
Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
> ---
> drivers/regulator/core.c | 58 ++++++++++++++++++++++++----------------
> 1 file changed, 35 insertions(+), 23 deletions(-)
>
> diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
> index 77f60eef960..2ff0ab2730f 100644
> --- a/drivers/regulator/core.c
> +++ b/drivers/regulator/core.c
> @@ -5391,6 +5391,7 @@ regulator_register(const struct regulator_desc *regulator_desc,
> bool dangling_of_gpiod = false;
> struct device *dev;
> int ret, i;
> + bool resolved_early = false;
>
> if (cfg == NULL)
> return ERR_PTR(-EINVAL);
> @@ -5494,24 +5495,10 @@ regulator_register(const struct regulator_desc *regulator_desc,
> BLOCKING_INIT_NOTIFIER_HEAD(&rdev->notifier);
> INIT_DELAYED_WORK(&rdev->disable_work, regulator_disable_work);
>
> - /* preform any regulator specific init */
> - if (init_data && init_data->regulator_init) {
> - ret = init_data->regulator_init(rdev->reg_data);
> - if (ret < 0)
> - goto clean;
> - }
> -
> - if (config->ena_gpiod) {
> - ret = regulator_ena_gpio_request(rdev, config);
> - if (ret != 0) {
> - rdev_err(rdev, "Failed to request enable GPIO: %pe\n",
> - ERR_PTR(ret));
> - goto clean;
> - }
> - /* The regulator core took over the GPIO descriptor */
> - dangling_cfg_gpiod = false;
> - dangling_of_gpiod = false;
> - }
> + if (init_data && init_data->supply_regulator)
> + rdev->supply_name = init_data->supply_regulator;
> + else if (regulator_desc->supply_name)
> + rdev->supply_name = regulator_desc->supply_name;
>
> /* register with sysfs */
> rdev->dev.class = ®ulator_class;
> @@ -5533,13 +5520,38 @@ regulator_register(const struct regulator_desc *regulator_desc,
> goto wash;
> }
>
> - if (init_data && init_data->supply_regulator)
> - rdev->supply_name = init_data->supply_regulator;
> - else if (regulator_desc->supply_name)
> - rdev->supply_name = regulator_desc->supply_name;
> + if ((rdev->supply_name && !rdev->supply) &&
> + (rdev->constraints->always_on ||
> + rdev->constraints->boot_on)) {
> + ret = regulator_resolve_supply(rdev);
> + if (ret != 0)
> + rdev_dbg(rdev, "Unable to resolve supply early: %pe\n",
> + ERR_PTR(ret));
> +
> + resolved_early = true;
> + }
> +
> + /* perform any regulator specific init */
> + if (init_data && init_data->regulator_init) {
> + ret = init_data->regulator_init(rdev->reg_data);
> + if (ret < 0)
> + goto wash;
> + }
> +
> + if (config->ena_gpiod) {
> + ret = regulator_ena_gpio_request(rdev, config);
> + if (ret != 0) {
> + rdev_err(rdev, "Failed to request enable GPIO: %pe\n",
> + ERR_PTR(ret));
> + goto wash;
> + }
> + /* The regulator core took over the GPIO descriptor */
> + dangling_cfg_gpiod = false;
> + dangling_of_gpiod = false;
> + }
>
> ret = set_machine_constraints(rdev);
> - if (ret == -EPROBE_DEFER) {
> + if (ret == -EPROBE_DEFER && !resolved_early) {
> /* Regulator might be in bypass mode and so needs its supply
> * to set the constraints
> */
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
