From: Trent Piepho <tpiepho@impinj.com>
To: "broonie@kernel.org" <broonie@kernel.org>
Cc: "linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"phil@raspberrypi.org" <phil@raspberrypi.org>
Subject: Re: [PATCH] spi: Make GPIO CSs honour the SPI_NO_CS flag
Date: Tue, 16 Oct 2018 19:29:21 +0000 [thread overview]
Message-ID: <1539718160.30311.10.camel@impinj.com> (raw)
In-Reply-To: <20181016090310.GA7449@sirena.org.uk>
On Tue, 2018-10-16 at 10:03 +0100, Mark Brown wrote:
> On Mon, Oct 15, 2018 at 06:34:18PM +0000, Trent Piepho wrote:
>
> > What about the calls to spi->controller->set_cs() after this? Should a
> > driver provided set_cs method be responsible for checking SPI_NO_CS?
> > Or should it not be called in the first place?
>
> This seems like something that should be done entirely in the framework,
> no point in every single driver having to open code the same thing.
>
> > I imagine it depends on what set_cs needs to do, which might not be
> > solely related to changing the CS line.
>
> It should be. If something is hanging other work on set_cs() then it's
> going to break.
IIRC, for spi-dw setting CS is the only way to trigger the master to do
anything. I think orion is the same way. Even if you don't want a CS
line the driver still needs to assert one. Which CS to use as the
dummy CS is a challenge that has come up before.
bcm2835_spi_set_cs() does check SPI_NO_CS, but it still does a lot of
other stuff even if that is set, likely because of the above issue.
next prev parent reply other threads:[~2018-10-16 19:29 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-12 9:23 [PATCH] spi: Make GPIO CSs honour the SPI_NO_CS flag Phil Elwell
2018-10-12 17:03 ` Applied "spi: Make GPIO CSs honour the SPI_NO_CS flag" to the spi tree Mark Brown
2018-10-15 18:34 ` [PATCH] spi: Make GPIO CSs honour the SPI_NO_CS flag Trent Piepho
2018-10-16 9:03 ` Mark Brown
2018-10-16 19:29 ` Trent Piepho [this message]
2018-10-17 9:42 ` Mark Brown
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