diff options
| author | Linus Walleij | 2019-12-04 23:57:31 +0100 |
|---|---|---|
| committer | Alexandre Belloni | 2019-12-10 17:47:16 +0100 |
| commit | 3b52093dc9175f48b275a02919149a2dff3a386d (patch) | |
| tree | 395697973e4585e59e7ce5a665f09f6d6effcab8 /drivers/rtc | |
| parent | 519d63702d0e710fd02dabce1370eaa24dfb5fc8 (diff) | |
rtc: ds1343: Do not hardcode SPI mode flags
The current use of mode flags to us SPI_MODE_3 and
SPI_CS_HIGH is fragile: it overwrites anything already
assigned by the SPI core. Change it thusly:
- Just |= the SPI_MODE_3 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>
Link: https://lore.kernel.org/r/20191204225731.20306-1-linus.walleij@linaro.org
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Diffstat (limited to 'drivers/rtc')
| -rw-r--r-- | drivers/rtc/rtc-ds1343.c | 7 |
1 files changed, 5 insertions, 2 deletions
diff --git a/drivers/rtc/rtc-ds1343.c b/drivers/rtc/rtc-ds1343.c index d21004a68ee0..530e64442b92 100644 --- a/drivers/rtc/rtc-ds1343.c +++ b/drivers/rtc/rtc-ds1343.c @@ -365,9 +365,12 @@ static int ds1343_probe(struct spi_device *spi) priv->spi = spi; /* RTC DS1347 works in spi mode 3 and - * its chip select is active high + * 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. */ - spi->mode = SPI_MODE_3 | SPI_CS_HIGH; + spi->mode |= SPI_MODE_3; + spi->mode ^= SPI_CS_HIGH; spi->bits_per_word = 8; res = spi_setup(spi); if (res) |