linux-kernel - Re: [PATCH] spi: sun6i: Add support for GPIO chip select lines

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Message-Id: <7d6d1494-31a7-4780-85f3-8bbc2f32bcd6@www.fastmail.com>
Date:   Sun, 10 May 2020 21:52:27 -0700
From:   Alistair <alistair@...stair23.me>
To:     "Geert Uytterhoeven" <geert@...ux-m68k.org>
Cc:     "Mark Brown" <broonie@...nel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
        "Maxime Ripard" <mripard@...nel.org>,
        "Chen-Yu Tsai" <wens@...e.org>,
        "Alistair Francis" <alistair23@...il.com>,
        "Linux ARM" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] spi: sun6i: Add support for GPIO chip select lines

On Wed, May 6, 2020, at 1:27 AM, Geert Uytterhoeven wrote:
> Hi Alistair,
> 
> On Wed, May 6, 2020 at 3:41 AM Alistair Francis <alistair@...stair23.me> wrote:
> > Add a setup function that can be used to support using generic GPIO
> > lines for the chip select.
> >
> > Signed-off-by: Alistair Francis <alistair@...stair23.me>
> > ---
> > drivers/spi/spi-sun6i.c | 27 +++++++++++++++++++++++++++
> > 1 file changed, 27 insertions(+)
> >
> > diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c
> > index ec7967be9e2f..fd4e19434942 100644
> > --- a/drivers/spi/spi-sun6i.c
> > +++ b/drivers/spi/spi-sun6i.c
> > @@ -10,6 +10,7 @@
> > #include <linux/clk.h>
> > #include <linux/delay.h>
> > #include <linux/device.h>
> > +#include <linux/gpio.h>
> > #include <linux/interrupt.h>
> > #include <linux/io.h>
> > #include <linux/module.h>
> > @@ -171,6 +172,31 @@ static inline void sun6i_spi_fill_fifo(struct sun6i_spi *sspi, int len)
> > }
> > }
> >
> > +static int sun6i_spi_setup(struct spi_device *spi)
> > +{
> > + int ret;
> > +
> > + /* sanity check for native cs */
> > + if (spi->mode & SPI_NO_CS)
> > + return 0;
> > + if (gpio_is_valid(spi->cs_gpio)) {
> > + /* with gpio-cs set the GPIO to the correct level
> > + * and as output (in case the dt has the gpio not configured
> > + * as output but native cs)
> > + */
> > + ret = gpio_direction_output(spi->cs_gpio,
> > + (spi->mode & SPI_CS_HIGH) ? 0 : 1);
> > + if (ret)
> > + dev_err(&spi->dev,
> > + "could not set gpio %i as output: %i\n",
> > + spi->cs_gpio, ret);
> > +
> > + return ret;
> > + }
> > +
> > + return 0;
> > +}
> > +
> > static void sun6i_spi_set_cs(struct spi_device *spi, bool enable)
> > {
> > struct sun6i_spi *sspi = spi_master_get_devdata(spi->master);
> > @@ -470,6 +496,7 @@ static int sun6i_spi_probe(struct platform_device *pdev)
> >
> > master->max_speed_hz = 100 * 1000 * 1000;
> > master->min_speed_hz = 3 * 1000;
> > + master->setup = sun6i_spi_setup;
> > master->set_cs = sun6i_spi_set_cs;
> > master->transfer_one = sun6i_spi_transfer_one;
> > master->num_chipselect = 4;
> 
> Can't you just set
> 
>  master->use_gpio_descriptors = true;
> 
> instead and be done with it?
> Then drivers/spi/spi.c:spi_get_gpio_descs() will configure the GPIO line
> as output for you.

Yep, it looks like that works. Sending a v2.

Alistair

> 
> Gr{oetje,eeting}s,
> 
>  Geert
> 
> -- 
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>  -- Linus Torvalds
>