linux-kernel - [PATCH v3] iio: filter: admv8818: Force initialization of SDO

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Message-ID:
 <SA1P110MB106904C961B0F3FAFFED74C0BCF5A@SA1P110MB1069.NAMP110.PROD.OUTLOOK.COM>
Date: Mon, 3 Feb 2025 13:34:34 +0000
From: Sam Winchenbach <swinchenbach@...a.org>
To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
	"antoniu.miclaus@...log.com" <antoniu.miclaus@...log.com>, "lars@...afoo.de"
	<lars@...afoo.de>, "Michael.Hennerich@...log.com"
	<Michael.Hennerich@...log.com>, "jic23@...nel.org" <jic23@...nel.org>
Subject: [PATCH v3] iio: filter: admv8818: Force initialization of SDO

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: f34fe888ad05 ("iio:filter:admv8818: add support for ADMV8818")
Signed-off-by: Sam Winchenbach <swinchenbach@...a.org>
---
 drivers/iio/filter/admv8818.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/filter/admv8818.c b/drivers/iio/filter/admv8818.c
index 195e58bc4..9cd1eee84 100644
--- a/drivers/iio/filter/admv8818.c
+++ b/drivers/iio/filter/admv8818.c
@@ -577,21 +577,15 @@ 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;
-- 
2.48.1