iio: filter: admv8818: Force initialization of SDO

commit cc2c354 upstream.

When a weak pull-up is present on the SDO line, regmap_update_bits fails
to write both the SOFTRESET and SDOACTIVE bits because it incorrectly
reads them as already set.

Since the soft reset disables the SDO line, performing a
read-modify-write operation on ADI_SPI_CONFIG_A to enable the SDO line
doesn't make sense. This change directly writes to the register instead
of using regmap_update_bits.

Fixes: f34fe88 ("iio:filter:admv8818: add support for ADMV8818")
Signed-off-by: Sam Winchenbach <swinchenbach@arka.org>
Link: https://patch.msgid.link/SA1P110MB106904C961B0F3FAFFED74C0BCF5A@SA1P110MB1069.NAMP110.PROD.OUTLOOK.COM
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Sam Winchenbach

drivers/iio/filter/admv8818.c

@@ -574,21 +574,15 @@ static int admv8818_init(struct admv8818_state *st)
 	struct spi_device *spi = st->spi;
 	unsigned int chip_id;
 
-	ret = regmap_update_bits(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
-				 ADMV8818_SOFTRESET_N_MSK |
-				 ADMV8818_SOFTRESET_MSK,
-				 FIELD_PREP(ADMV8818_SOFTRESET_N_MSK, 1) |
-				 FIELD_PREP(ADMV8818_SOFTRESET_MSK, 1));
+	ret = regmap_write(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
+			   ADMV8818_SOFTRESET_N_MSK | ADMV8818_SOFTRESET_MSK);
 	if (ret) {
 		dev_err(&spi->dev, "ADMV8818 Soft Reset failed.\n");
 		return ret;
 	}
 
-	ret = regmap_update_bits(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
-				 ADMV8818_SDOACTIVE_N_MSK |
-				 ADMV8818_SDOACTIVE_MSK,
-				 FIELD_PREP(ADMV8818_SDOACTIVE_N_MSK, 1) |
-				 FIELD_PREP(ADMV8818_SDOACTIVE_MSK, 1));
+	ret = regmap_write(st->regmap, ADMV8818_REG_SPI_CONFIG_A,
+			   ADMV8818_SDOACTIVE_N_MSK | ADMV8818_SDOACTIVE_MSK);
 	if (ret) {
 		dev_err(&spi->dev, "ADMV8818 SDO Enable failed.\n");
 		return ret;