From: Stefan Wahren <stefan.wahren@i2se.com>
To: Lukas Wunner <lukas@wunner.de>
Cc: linux-gpio@vger.kernel.org, Eric Anholt <eric@anholt.net>,
Linus Walleij <linus.walleij@linaro.org>,
Bartosz Golaszewski <bgolaszewski@baylibre.com>,
Peter Robinson <pbrobinson@gmail.com>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH RFC V2 3/4] pinctrl: bcm2835: activate strict mux mode
Date: Mon, 21 Jan 2019 10:57:37 +0100 [thread overview]
Message-ID: <db62122f-00fc-b251-6fa7-7d02a4d7d9c5@i2se.com> (raw)
In-Reply-To: <20190121073419.iosy3bd6tcnexya7@wunner.de>
Am 21.01.19 um 08:34 schrieb Lukas Wunner:
> On Mon, Jan 21, 2019 at 08:11:24AM +0100, Stefan Wahren wrote:
>> This activates strict mode muxing for the bcm2835 pin controller,
>> as the GPIO Function Select Registers do not allow GPIO and functions
>> at the same time.
> bcm2835_spi_setup() in spi-bcm2835.c converts a native chip select
> to a gpio chip select. So pins 7+8 and/or 35+36 may be set to
> function alt0 but in reality the pins are requested and driven as
> generic output gpio pins.
>
> I'm not sure but doesn't this break in strict mode?
That's a good point. I hope that isn't a problem because owner should be
the same.
But i didn't test this scenario. Do you mind to give this series a try?
The only issue i found so far was a unnecessary pinctrl on the Raspberry
Pi Zero W, which should be fixed with this [1].
At the end we need to switch to strict mode, because currently a simple
gpioset can "destroy" the mux setting for I2C or SPI.
[1] - https://marc.info/?l=linux-arm-kernel&m=154800402627578
>
> Thanks,
>
> Lukas
>
next prev parent reply other threads:[~2019-01-21 9:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-21 7:11 [PATCH RFC V2 0/4] pinctrl: bcm2835: improve libgpiod output Stefan Wahren
2019-01-21 7:11 ` [PATCH RFC V2 1/4] pinctrl: bcm2835: declare pin config as generic Stefan Wahren
2019-01-28 8:02 ` Linus Walleij
2019-01-21 7:11 ` [PATCH RFC V2 2/4] pinctrl: bcm2835: Direct GPIO config changes to generic pinctrl Stefan Wahren
2019-01-21 7:11 ` [PATCH RFC V2 3/4] pinctrl: bcm2835: activate strict mux mode Stefan Wahren
[not found] ` <20190121073419.iosy3bd6tcnexya7@wunner.de>
2019-01-21 9:57 ` Stefan Wahren [this message]
2019-01-21 7:11 ` [PATCH RFC V2 4/4] gpiolib: Take MUX usage into account Stefan Wahren
2019-01-28 9:06 ` Linus Walleij
2019-01-28 8:06 ` [PATCH RFC V2 0/4] pinctrl: bcm2835: improve libgpiod output Linus Walleij
2019-01-28 9:23 ` Stefan Wahren
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