From: Ulf Hansson <ulf.hansson@linaro.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: "linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
Phil Elwell <phil@raspberrypi.org>,
Mark Brown <broonie@kernel.org>
Subject: Re: [PATCH] mmc: spi: Toggle SPI polarity, do not hardcode it
Date: Mon, 16 Dec 2019 13:09:12 +0100 [thread overview]
Message-ID: <CAPDyKFotLu_SxpKEPBWgPjrR0+57Ou6VRL=egPGvJVMSr4vCGw@mail.gmail.com> (raw)
In-Reply-To: <CACRpkdai6FwgwD7+BeF0_ORw4P1hoCv4dvoi_Uhyp21t5qCOjw@mail.gmail.com>
On Wed, 11 Dec 2019 at 00:11, Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Tue, Dec 10, 2019 at 10:52 AM Ulf Hansson <ulf.hansson@linaro.org> wrote:
> > On Wed, 4 Dec 2019 at 16:29, Linus Walleij <linus.walleij@linaro.org> wrote:
> > >
> > > The code in mmc_spi_initsequence() tries to send a burst with
> > > high chipselect and for this reason hardcodes the device into
> > > SPI_CS_HIGH.
> > >
> > > This is not good because the SPI_CS_HIGH flag indicates
> > > logical "asserted" CS not always the physical level. In
> > > some cases the signal is inverted in the GPIO library and
> > > in that case SPI_CS_HIGH is already set, and enforcing
> > > SPI_CS_HIGH again will actually drive it low.
> > >
> > > Instead of hard-coding this, toggle the polarity so if the
> > > default is LOW it goes high to assert chipselect but if it
> > > is already high then toggle it low instead.
> > >
> > > Cc: Phil Elwell <phil@raspberrypi.org>
> > > Reported-by: Mark Brown <broonie@kernel.org>
> > > Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> >
> > Seems like we should add a stable tag, right?
>
> Yeah I agree.
Alright. I have amended the patch to add the tag.
Kind regards
Uffe
prev parent reply other threads:[~2019-12-16 12:09 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-04 15:27 [PATCH] mmc: spi: Toggle SPI polarity, do not hardcode it Linus Walleij
2019-12-04 17:20 ` Mark Brown
2019-12-10 9:51 ` Ulf Hansson
2019-12-10 23:10 ` Linus Walleij
2019-12-16 12:09 ` Ulf Hansson [this message]
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