From: Linus Walleij <linus.walleij@linaro.org>
To: lee.jones@linaro.org, linux-kernel@vger.kernel.org
Cc: Linus Walleij <linus.walleij@linaro.org>,
Mark Brown <broonie@kernel.org>
Subject: [PATCH] mfd: mc13xxx-spi: Do not hardcode SPI mode flags
Date: Wed, 4 Dec 2019 16:27:15 +0100 [thread overview]
Message-ID: <20191204152715.12553-1-linus.walleij@linaro.org> (raw)
The current use of mode flags to us SPI_MODE_0 and
SPI_CS_HIGH is fragile: it overwrites anything already
assigned by the SPI core. Change it thusly:
- Just |= the SPI_MODE_0 so we keep other flags
- Assign ^= SPI_CS_HIGH since we might be active high
already, and that is usually the case with GPIOs used
for chip select, even if they are in practice active low.
Add a comment clarifying why ^= SPI_CS_HIGH is the right
choice here.
Reported-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
---
drivers/mfd/mc13xxx-spi.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/mfd/mc13xxx-spi.c b/drivers/mfd/mc13xxx-spi.c
index 286ddcf5ddc6..9885e5f8210a 100644
--- a/drivers/mfd/mc13xxx-spi.c
+++ b/drivers/mfd/mc13xxx-spi.c
@@ -134,7 +134,13 @@ static int mc13xxx_spi_probe(struct spi_device *spi)
dev_set_drvdata(&spi->dev, mc13xxx);
- spi->mode = SPI_MODE_0 | SPI_CS_HIGH;
+ spi->mode |= SPI_MODE_0;
+ /*
+ * We want the inverse of what is set in the SPI core, if this
+ * is accomplished with a GPIO line then inversion semantics may
+ * be handled in the GPIO library.
+ */
+ spi->mode ^= SPI_CS_HIGH;
mc13xxx->irq = spi->irq;
--
2.23.0
reply other threads:[~2019-12-04 15:29 UTC|newest]
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