| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.5 166/189] regulator: stm32-vrefbuf: fix a possible overshoot when re-enabling | Date | Tue, 10 Mar 2020 13:40:03 +0100 |
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From: Fabrice Gasnier <fabrice.gasnier@st.com>
commit 02fbabd5f4ed182d2c616e49309f5a3efd9ec671 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: 0cdbf481e927 ("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>
--- drivers/regulator/stm32-vrefbuf.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/regulator/stm32-vrefbuf.c +++ b/drivers/regulator/stm32-vrefbuf.c @@ -88,7 +88,7 @@ static int stm32_vrefbuf_disable(struct } 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 .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, };
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