On Mon, Nov 26, 2018 at 05:27:47PM +0200, Priit Laes wrote:
> From: Olliver Schinagl <oliver@xxxxxxxxxxx>
>
> In the past, there have been words on various lists that if LDO3 is
> disabled in u-boot, but enabled in the DTS, the axp209 driver would
> fail to continue/hang. Several enable/disable patches have been
> issues to devicetree's in both the kernel and u-boot to address
> this issue.
>
> What really happened however, was that the AXP209 shuts down without
> a notice and without setting an interrupt. This is caused when LDO3
> gets overloaded, for example with large capacitors on the LDO3 output.
>
> Normally, we would expect that AXP209 would source 200 mA as per
> datasheet and set and trigger an interrupt when being overloaded.
> For some reason however, this does not happen.
>
> As a work-around, we use the soft-start constraint of the regulator
> node to first bring up the LDO3 to the lowest possible voltage and
> then enable the LDO. After that, we can set the requested voltage
> as usual.
>
> Combining this setting with the regulator-ramp-delay allows LDO3 to
> enable voltage slowly and staggered, potentially reducing overall
> inrush current.
>
> Signed-off-by: Olliver Schinagl <oliver@xxxxxxxxxxx>
> Signed-off-by: Priit Laes <plaes@xxxxxxxxx>
> ---
> drivers/regulator/axp20x-regulator.c | 57 ++++++++++++++++++++++++++++-
> 1 file changed, 56 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/regulator/axp20x-regulator.c b/drivers/regulator/axp20x-regulator.c
> index 1d9fa62..e8a895b 100644
> --- a/drivers/regulator/axp20x-regulator.c
> +++ b/drivers/regulator/axp20x-regulator.c
> @@ -14,6 +14,7 @@
> */
>
> #include <linux/bitops.h>
> +#include <linux/delay.h>
> #include <linux/err.h>
> #include <linux/init.h>
> #include <linux/mfd/axp20x.h>
> @@ -23,6 +24,7 @@
> #include <linux/platform_device.h>
> #include <linux/regmap.h>
> #include <linux/regulator/driver.h>
> +#include <linux/regulator/machine.h>
> #include <linux/regulator/of_regulator.h>
>
> #define AXP20X_GPIO0_FUNC_MASK GENMASK(3, 0)
> @@ -430,6 +432,59 @@ static int axp20x_set_ramp_delay(struct regulator_dev *rdev, int ramp)
> return regmap_update_bits(axp20x->regmap, reg, mask, cfg);
> }
>
> +static int axp20x_regulator_enable_regmap(struct regulator_dev *rdev)
> +{
> + struct axp20x_dev *axp20x = rdev_get_drvdata(rdev);
> + const struct regulator_desc *desc = rdev->desc;
> +
> + if (!rdev)
> + return -EINVAL;
> +
> + switch (axp20x->variant) {
> + case AXP209_ID:
> + if ((desc->id == AXP20X_LDO3) &&
> + rdev->constraints && rdev->constraints->soft_start) {
> + int v_out;
> + int ret;
> +
> + /*
> + * On some boards, the LDO3 can be overloaded when
> + * turning on, causing the entire PMIC to shutdown
> + * without warning. Turning it on at the minimal voltage
> + * and then setting the voltage to the requested value
> + * works reliably.
> + */
> + if (regulator_is_enabled_regmap(rdev))
> + break;
> +
> + v_out = regulator_get_voltage_sel_regmap(rdev);
> + if (v_out < 0)
> + return v_out;
> +
> + if (v_out == 0)
> + break;
> +
> + ret = regulator_set_voltage_sel_regmap(rdev, 0x00);
> + /*
> + * A small pause is needed between
> + * setting the voltage and enabling the LDO to give the
> + * internal state machine time to process the request.
> + */
> + usleep_range(1000, 5000);
> + ret |= regulator_enable_regmap(rdev);
> + ret |= regulator_set_voltage_sel_regmap(rdev, v_out);
> +
> + return ret;
> + }
> + break;
> + default:
> + /* No quirks */
> + break;
> + }
> +
> + return regulator_enable_regmap(rdev);
> +};
> +
This is some pretty generic code, and could be useful to some other
users. I guess a generic function would be better for this.
Maxime
--
Maxime Ripard, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
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