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>

1 files changed, 13 insertions, 2 deletions

diff --git a/drivers/spi/spi-imx.c b/drivers/spi/spi-imx.c
index 0e5723ab47f0..e7e4f0c0f14d 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;
 
         init_completion(&spi_imx->xfer_done);