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From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 13 Sep 2018 15:44:43 +0200
Message-ID: <CAMuHMdUb=sXBBRLhKNxsWT_Z4PCoLcM16NajvmPVHWsvgoL7_w@mail.gmail.com>
Subject: Re: [PATCH v2 4/4] spi: spi-davinci: Add support for SPI_CS_WORD
To: David Lechner <david@lechnology.com>
Cc: linux-spi <linux-spi@vger.kernel.org>, linux-iio@vger.kernel.org,
	Jonathan Cameron <jic23@kernel.org>, Hartmut Knaack <knaack.h@gmx.de>, Lars-Peter Clausen <lars@metafoo.de>,
	Peter Meerwald <pmeerw@pmeerw.net>, Mark Brown <broonie@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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List-ID: <linux-iio@vger.kernel.org>

Hi David,

On Thu, Sep 13, 2018 at 2:40 AM David Lechner <david@lechnology.com> wrote:
> This adds support for the SPI_CS_WORD flag to the TI DaVinci SPI
> driver. This mode can be used as long as we are using the hardware
> chip select and not a GPIO chip select.
>
> Signed-off-by: David Lechner <david@lechnology.com>
> ---
>  drivers/spi/spi-davinci.c | 11 ++++++++---
>  1 file changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/spi/spi-davinci.c b/drivers/spi/spi-davinci.c
> index d502cf504deb..8f7dcbc53c57 100644
> --- a/drivers/spi/spi-davinci.c
> +++ b/drivers/spi/spi-davinci.c
> @@ -230,7 +230,8 @@ static void davinci_spi_chipselect(struct spi_device *spi, int value)
>                                 !(spi->mode & SPI_CS_HIGH));
>         } else {
>                 if (value == BITBANG_CS_ACTIVE) {
> -                       spidat1 |= SPIDAT1_CSHOLD_MASK;
> +                       if (!(spi->mode & SPI_CS_WORD))
> +                               spidat1 |= SPIDAT1_CSHOLD_MASK;
>                         spidat1 &= ~(0x1 << chip_sel);
>                 }
>         }
> @@ -440,8 +441,12 @@ static int davinci_spi_setup(struct spi_device *spi)
>                         return retval;
>                 }
>
> -               if (internal_cs)
> +               if (internal_cs) {
>                         set_io_bits(dspi->base + SPIPC0, 1 << spi->chip_select);
> +               } else if (spi->mode & SPI_CS_WORD) {
> +                       dev_err(&spi->dev, "SPI_CS_WORD can't be use with GPIO CS\n");
> +                       return -EINVAL;

Does the SPI core fall back to splitting the transfer in this case?

> +               }

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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