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

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Date:   Wed, 6 May 2020 10:27:23 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Alistair Francis <alistair@...stair23.me>
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>, alistair23@...il.com,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] spi: sun6i: Add support for GPIO chip select lines

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.

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