Re: [PATCH] spi-imx: Add loopback mode support

[Fabio Estevam <festevam@xxxxxxxxx>]

On Thu, Dec 3, 2015 at 11:23 PM, Fabio Estevam <festevam@xxxxxxxxx> wrote:
> From: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx>
>
> Loopback mode can be activated by setting bit LBC (LoopBack
> Control) of register ECSPI_TESTREG.
>
> Add support for it.
>
> Signed-off-by: Fabio Estevam <fabio.estevam@xxxxxxxxxxxxx>
> ---
>  drivers/spi/spi-imx.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
> index 0e5723a..e7e4f0c 100644
> --- a/drivers/spi/spi-imx.c
> +++ b/drivers/spi/spi-imx.c
> @@ -244,6 +244,9 @@ static bool spi_imx_can_dma(struct spi_master *master, struct spi_device *spi,
>  #define MX51_ECSPI_STAT                0x18
>  #define MX51_ECSPI_STAT_RR             (1 <<  3)
>
> +#define MX51_ECSPI_TESTREG     0x20
> +#define MX51_ECSPI_TESTREG_LBC BIT(31)
> +
>  /* MX51 eCSPI */
>  static unsigned int mx51_ecspi_clkdiv(unsigned int fin, unsigned int fspi,
>                                       unsigned int *fres)
> @@ -313,7 +316,7 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>  {
>         u32 ctrl = MX51_ECSPI_CTRL_ENABLE, cfg = 0, dma = 0;
>         u32 tx_wml_cfg, rx_wml_cfg, rxt_wml_cfg;
> -       u32 clk = config->speed_hz, delay;
> +       u32 clk = config->speed_hz, delay, reg;
>
>         /*
>          * The hardware seems to have a race condition when changing modes. The
> @@ -351,6 +354,13 @@ static int __maybe_unused mx51_ecspi_config(struct spi_imx_data *spi_imx,
>         else
>                 cfg &= ~MX51_ECSPI_CONFIG_SSBPOL(config->cs);
>
> +       reg = readl(spi_imx->base + MX51_ECSPI_TESTREG);
> +       if (config->mode & SPI_LOOP)
> +               reg |= MX51_ECSPI_TESTREG_LBC;
> +       else
> +               reg &= ~MX51_ECSPI_TESTREG_LBC;
> +       writel(reg, spi_imx->base + MX51_ECSPI_TESTREG);
> +
>         writel(ctrl, spi_imx->base + MX51_ECSPI_CTRL);
>         writel(cfg, spi_imx->base + MX51_ECSPI_CONFIG);
>
> @@ -1141,7 +1151,8 @@ static int spi_imx_probe(struct platform_device *pdev)
>         spi_imx->bitbang.master->cleanup = spi_imx_cleanup;
>         spi_imx->bitbang.master->prepare_message = spi_imx_prepare_message;
>         spi_imx->bitbang.master->unprepare_message = spi_imx_unprepare_message;
> -       spi_imx->bitbang.master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
> +       spi_imx->bitbang.master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH |
> +                                            SPI_LOOP;

The SPI_LOOP should not be added to all spi versions, only for the
mx51/mx53/mx6q type.

Just realized that Anton sent the loopback support as part of his
series, so please discard this one.
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