From: Linus Walleij <linus.walleij@linaro.org>
To: Tony Lindgren <tony@atomide.com>
Cc: Lee Jones <lee.jones@linaro.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Mark Brown <broonie@kernel.org>,
Sebastian Reichel <sre@kernel.org>
Subject: Re: [PATCH] mfd: motorola-cpcap: Do not hardcode SPI mode flags
Date: Tue, 7 Jan 2020 10:57:10 +0100 [thread overview]
Message-ID: <CACRpkdYm2b7G6dvmY5VCSSQCK6DMEYMYRqnoMpH6jaumkQL3Xg@mail.gmail.com> (raw)
In-Reply-To: <20191219170409.GH35479@atomide.com>
On Thu, Dec 19, 2019 at 6:04 PM Tony Lindgren <tony@atomide.com> wrote:
> * Linus Walleij <linus.walleij@linaro.org> [700101 00:00]:
> > 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.
>
> Looks like this breaks booting for droid4 with a cpcap
> PMIC, probably as regulators won't work. There's no GPIO
> controller involved in this case for the chip select, the
> pins are directly controlled by the spi-omap2-mcspi.c
> driver.
>
> From the pin muxing setup we see there's a pull-down on
> mcspi1_cs0 pin meaning it's active high:
>
> /* 0x4a100138 mcspi1_cs0.mcspi1_cs0 ae23 */
> OMAP4_IOPAD(0x138, PIN_INPUT_PULLDOWN | MUX_MODE0)
>
> My guess a similar issue is with similar patches for
> all non-gpio spi controllers?
>
> Let me know if you want me to test some other changes,
> or if this patch depends on some other changes.
So this must mean that something else is setting SPI_CS_HIGH
for this driver, such as the device tree, right?
And the |= SPI_CS_HIGH assignment in the driver is just
surplus and we should just delete this code instead.
Would that be right?
Yours,
Linus Walleij
next prev parent reply other threads:[~2020-01-07 9:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-04 23:19 [PATCH] mfd: motorola-cpcap: Do not hardcode SPI mode flags Linus Walleij
2019-12-19 17:04 ` Tony Lindgren
2020-01-07 9:57 ` Linus Walleij [this message]
2020-01-07 18:24 ` Tony Lindgren
2020-01-07 18:37 ` Tony Lindgren
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