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regulator: stm32-vrefbuf: fix a possible overshoot when re-enabling 

commit 02fbabd5f4 upstream.

There maybe an overshoot, when disabling, then re-enabling vrefbuf
too quickly. VREFBUF is used by ADC/DAC on some boards. When re-enabling
too quickly, an overshoot on the reference voltage make the conversions
inaccurate for a short period of time.
- Don't put the VREFBUF in HiZ when disabling, to force an active
discharge.
- Enforce a 1ms OFF/ON delay

Fixes: 0cdbf481e9 ("regulator: Add support for stm32-vrefbuf")

Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Message-Id: <1583312132-20932-1-git-send-email-fabrice.gasnier@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
5.4-rM2-2.2.x-imx-squashed
Fabrice Gasnier 2020-03-04 09:55:32 +01:00 committed by Greg Kroah-Hartman
parent baec58de4a
commit 3d5d75f8c2
1 changed files with 2 additions and 1 deletions
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3
drivers/regulator/stm32-vrefbuf.c
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@ -88,7 +88,7 @@ static int stm32_vrefbuf_disable(struct regulator_dev *rdev)
}
val = readl_relaxed(priv->base + STM32_VREFBUF_CSR);
val = (val & ~STM32_ENVR) | STM32_HIZ;
val &= ~STM32_ENVR;
writel_relaxed(val, priv->base + STM32_VREFBUF_CSR);
pm_runtime_mark_last_busy(priv->dev);
@ -175,6 +175,7 @@ static const struct regulator_desc stm32_vrefbuf_regu = {
.volt_table = stm32_vrefbuf_voltages,
.n_voltages = ARRAY_SIZE(stm32_vrefbuf_voltages),
.ops = &stm32_vrefbuf_volt_ops,
.off_on_delay = 1000,
.type = REGULATOR_VOLTAGE,
.owner = THIS_MODULE,
};