spi-imx: Add loopback mode support

From: Fabio Estevam <[email protected]>

Loopback mode can be activated by setting bit LBC (LoopBack Control) of register ECSPI_TESTREG.

Add support for it.

Signed-off-by Fabio Estevam <[email protected]>

---
 drivers/spi/spi-imx.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

drivers/spi/spi-imx.c +11 -1

index 0e5723a..e7e4f0c 100644
@@ -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);
 

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.

Quoted 5 lines · Fabio Estevam

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.

I'd already applied this before you sent your mail, sorry.

Quoted 1 line · Mark Brown

I'd already applied this before you sent your mail, sorry.

I'll rebase my changes on top of topic/imx. Is it OK?

Quoted 5 lines · Anton Bondarenko

Quoted 1 line · Mark Brown

I'd already applied this before you sent your mail, sorry.

I'll rebase my changes on top of topic/imx. Is it OK?

Yes, totally fine - please go ahead.

Quoted 5 lines · Fabio Estevam

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.

I'd already applied this before you sent your mail, sorry.

Quoted 8 lines · Mark Brown

Quoted 5 lines · Fabio Estevam

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.

Quoted 1 line

I'd already applied this before you sent your mail, sorry.

No problekm, Mark. I think Anton can move the SPI_LOOP flag from the probe function to only mx51/mx53/mx6 config and all will be fine.

Thanks

There is a small problem with this change. Loopback mode not enabled for first transaction in the system. This is happen because TEST reg written before controller taken out from the reset by writing to CTRL reg. The simple fix will be to move TEST reg read/write after write to CTRL reg.