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There maybe an overshoot:
- when disabling, then re-enabling vrefbuf too quickly
- or upon platform reset as external capacitor maybe slow
discharging (VREFBUF is HiZ at reset by default).
VREFBUF is used by ADC/DAC on some boards. An overshoot on the reference
voltage make the conversions inaccurate for a short period of time. So:
- Don't put the VREFBUF in HiZ when disabling, to force an active
discharge.
- Enforce a 1ms OFF/ON delay, also upon reset
Penalty is a 1ms delay is applied (even for a cold boot), when enabling
VREFBUF.
Fixes: 93cf0ae7758d ("power: regulator: Add support for stm32-vrefbuf")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Jaehoon Chung <jh80.chung@samsung.com>
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Move this uncommon header out of the common header.
Signed-off-by: Simon Glass <sjg@chromium.org>
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At present dm/device.h includes the linux-compatible features. This
requires including linux/compat.h which in turn includes a lot of headers.
One of these is malloc.h which we thus end up including in every file in
U-Boot. Apart from the inefficiency of this, it is problematic for sandbox
which needs to use the system malloc() in some files.
Move the compatibility features into a separate header file.
Signed-off-by: Simon Glass <sjg@chromium.org>
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This patch solves the following warnings:
drivers/power/regulator/stm32-vrefbuf.c: In function 'stm32_vrefbuf_set_value':
warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
if (uV == stm32_vrefbuf_voltages[i]) {
^~
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Patrick Delaunay <patrick.delaunay@st.com>
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Add regulator driver for STM32 voltage reference buffer which can be
used as voltage reference for ADCs, DACs and external components through
dedicated VREF+ pin.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
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