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: motorola-cpcap: Do not hardcode SPI mode flags
Date: Thu, 5 Dec 2019 00:19:31 +0100 [thread overview]
Message-ID: <20191204231931.21378-1-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/motorola-cpcap.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/drivers/mfd/motorola-cpcap.c b/drivers/mfd/motorola-cpcap.c
index 52f38e57cdc1..a3bc61b8008c 100644
--- a/drivers/mfd/motorola-cpcap.c
+++ b/drivers/mfd/motorola-cpcap.c
@@ -279,7 +279,13 @@ static int cpcap_probe(struct spi_device *spi)
spi_set_drvdata(spi, cpcap);
spi->bits_per_word = 16;
- spi->mode = SPI_MODE_0 | SPI_CS_HIGH;
+ spi->mode |= SPI_MODE_0;
+ /*
+ * 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_CS_HIGH;
ret = spi_setup(spi);
if (ret)
--
2.23.0
next reply other threads:[~2019-12-04 23:21 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-04 23:19 Linus Walleij [this message]
2019-12-19 17:04 ` [PATCH] mfd: motorola-cpcap: Do not hardcode SPI mode flags Tony Lindgren
2020-01-07 9:57 ` Linus Walleij
2020-01-07 18:24 ` Tony Lindgren
2020-01-07 18:37 ` Tony Lindgren
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20191204231931.21378-1-linus.walleij@linaro.org \
--to=linus.walleij@linaro.org \
--cc=broonie@kernel.org \
--cc=lee.jones@linaro.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).