linux-kernel - Re: [PATCH v2] spi: dw: support 4-16 bits per word

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Date:   Fri, 17 Aug 2018 14:17:08 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Simon Goldschmidt <simon.k.r.goldschmidt@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>
Cc:     Mark Brown <broonie@...nel.org>,
        linux-spi <linux-spi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] spi: dw: support 4-16 bits per word

On Fri, Aug 17, 2018 at 10:01 AM, Simon Goldschmidt
<simon.k.r.goldschmidt@...il.com> wrote:
> The spi-dw driver currently only supports 8 or 16 bits per word.
>
> Since the hardware supports 4-16 bits per word, adapt the driver
> to also support this.
>
> Tested on socfpga cyclone5 with a 9-bit SPI display.
>

LGTM,
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

> Signed-off-by: Simon Goldschmidt <simon.k.r.goldschmidt@...il.com>
> ---
>
> Changes in v2:
> - use DIV_ROUND_UP to calculate number of bytes per word instead of
>   if/else range checks
>
>  drivers/spi/spi-dw.c | 16 +++++++---------
>  1 file changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/spi/spi-dw.c b/drivers/spi/spi-dw.c
> index f693bfe95ab9..58a7caf31d59 100644
> --- a/drivers/spi/spi-dw.c
> +++ b/drivers/spi/spi-dw.c
> @@ -307,15 +307,13 @@ static int dw_spi_transfer_one(struct spi_controller *master,
>                 dws->current_freq = transfer->speed_hz;
>                 spi_set_clk(dws, chip->clk_div);
>         }
> -       if (transfer->bits_per_word == 8) {
> -               dws->n_bytes = 1;
> -               dws->dma_width = 1;
> -       } else if (transfer->bits_per_word == 16) {
> -               dws->n_bytes = 2;
> -               dws->dma_width = 2;
> -       } else {
> +
> +       if ((transfer->bits_per_word < 4) || (transfer->bits_per_word > 16))
>                 return -EINVAL;
> -       }
> +
> +       dws->n_bytes = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
> +       dws->dma_width = DIV_ROUND_UP(transfer->bits_per_word, BITS_PER_BYTE);
> +
>         /* Default SPI mode is SCPOL = 0, SCPH = 0 */
>         cr0 = (transfer->bits_per_word - 1)
>                 | (chip->type << SPI_FRF_OFFSET)
> @@ -493,7 +491,7 @@ int dw_spi_add_host(struct device *dev, struct dw_spi *dws)
>         }
>
>         master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP;
> -       master->bits_per_word_mask = SPI_BPW_MASK(8) | SPI_BPW_MASK(16);
> +       master->bits_per_word_mask =  SPI_BPW_RANGE_MASK(4, 16);
>         master->bus_num = dws->bus_num;
>         master->num_chipselect = dws->num_cs;
>         master->setup = dw_spi_setup;
> --
> 2.17.1
>



-- 
With Best Regards,
Andy Shevchenko