linux-kernel - [PATCH] rtc: ds1343: Force SPI chip select to be active high

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Date: Thu, 20 Jun 2024 14:05:14 +0100
From: Ian Abbott <abbotti@....co.uk>
To: linux-rtc@...r.kernel.org
Cc: Alexandre Belloni <alexandre.belloni@...tlin.com>,
	linux-kernel@...r.kernel.org,
	Ian Abbott <abbotti@....co.uk>,
	stable@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	Mark Brown <broonie@...nel.org>
Subject: [PATCH] rtc: ds1343: Force SPI chip select to be active high

Commit 3b52093dc917 ("rtc: ds1343: Do not hardcode SPI mode flags")
bit-flips (^=) the existing SPI_CS_HIGH setting in the SPI mode during
device probe.  This will set it to the wrong value if the spi-cs-high
property has been set in the devicetree node.  Just force it to be set
active high and get rid of some commentary that attempted to explain why
flipping the bit was the correct choice.

Fixes: 3b52093dc917 ("rtc: ds1343: Do not hardcode SPI mode flags")
Cc: <stable@...r.kernel.org> # 5.6+
Cc: Linus Walleij <linus.walleij@...aro.org>
Cc: Mark Brown <broonie@...nel.org>
Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
 drivers/rtc/rtc-ds1343.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/drivers/rtc/rtc-ds1343.c b/drivers/rtc/rtc-ds1343.c
index ed5a6ba89a3e..484b5756b55c 100644
--- a/drivers/rtc/rtc-ds1343.c
+++ b/drivers/rtc/rtc-ds1343.c
@@ -361,13 +361,10 @@ static int ds1343_probe(struct spi_device *spi)
 	if (!priv)
 		return -ENOMEM;
 
-	/* RTC DS1347 works in spi mode 3 and
-	 * its chip select is active high. Active high should be defined as
-	 * "inverse polarity" as GPIO-based chip selects can be logically
-	 * active high but inverted by the GPIO library.
+	/*
+	 * RTC DS1347 works in spi mode 3 and its chip select is active high.
 	 */
-	spi->mode |= SPI_MODE_3;
-	spi->mode ^= SPI_CS_HIGH;
+	spi->mode |= SPI_MODE_3 | SPI_CS_HIGH;
 	spi->bits_per_word = 8;
 	res = spi_setup(spi);
 	if (res)
-- 
2.43.0