From: Mark Brown <broonie@kernel.org>
To: Chris Packham <Chris.Packham@alliedtelesis.co.nz>
Cc: "robh+dt@kernel.org" <robh+dt@kernel.org>,
"mark.rutland@arm.com" <mark.rutland@arm.com>,
Hamish Martin <Hamish.Martin@alliedtelesis.co.nz>,
"linux-spi@vger.kernel.org" <linux-spi@vger.kernel.org>,
"devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tthayer@opensource.altera.com" <tthayer@opensource.altera.com>
Subject: Re: [PATCH 0/3] spi: SPI bus multiplexer
Date: Thu, 2 May 2019 11:45:24 +0900 [thread overview]
Message-ID: <20190502024524.GV14916@sirena.org.uk> (raw)
In-Reply-To: <d91ab2261a1f4069bc48e090bd4ec702@svr-chch-ex1.atlnz.lc>
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On Sun, Apr 28, 2019 at 10:28:16PM +0000, Chris Packham wrote:
> One other problem that I encounter is the interaction between cs-gpio
> and SPI_MASTER_GPIO_SS. Having cs-gpio automatically sets SPI_CS_HIGH
> which has the undesired side-effect that now my real chip select is
> inverted. I actually wonder if this change breaks commit 8eee6b9dd30d
> ("spi: Add Flag to Enable Slave Select with GPIO Chip Select.") since
> now there is an extra inversion on the CS enable.
That sounds like a framework bug which should just be fixed - we
shouldn't be disrupting users of real chip selects when using a GPIO
chip select. Depending on the hardware we might need a chip select
assigned that isn't connected to anything for use while the GPIOs are
doing the real work but otherwise we shouldn't be breaking things.
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prev parent reply other threads:[~2019-05-02 2:45 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-12 5:02 [PATCH 0/3] spi: SPI bus multiplexer Chris Packham
2019-04-12 5:02 ` [PATCH 1/3] dt-bindings: spi: Add spi-mux-gpio Chris Packham
2019-04-29 21:37 ` Rob Herring
2020-01-13 3:43 ` Chris Packham
2019-04-12 5:02 ` [PATCH 2/3] spi: Make of_find_spi_controller_by_node visible Chris Packham
2019-04-12 5:02 ` [PATCH 3/3] spi: Add SPI bus gpio multiplexer Chris Packham
2019-04-12 8:29 ` [PATCH 0/3] spi: SPI bus multiplexer Mark Brown
2019-04-28 22:28 ` Chris Packham
2019-05-02 2:45 ` Mark Brown [this message]
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