spi: imx: Add loopback mode support

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@freescale.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 0e5723a..e7e4f0c 100644 (file)
--- 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;
 
        init_completion(&spi_imx->xfer_done);