[PATCH V2 4/8] spi: lpspi: add the error info of transfer speed setting

[Clark Wang]

Add a error info when set a speed which greater than half of per-clk of
spi module.

The minimum SCK period is 2 cycles(CCR[SCKDIV]). So the maximum transfer
speed is half of spi per-clk.

Signed-off-by: Clark Wang <xiaoning.w...@nxp.com>
---
V2:
 - No change. Resend for applying.
---
 drivers/spi/spi-fsl-lpspi.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-fsl-lpspi.c b/drivers/spi/spi-fsl-lpspi.c
index 84dcb9e176b8..69635cde0e22 100644
--- a/drivers/spi/spi-fsl-lpspi.c
+++ b/drivers/spi/spi-fsl-lpspi.c
@@ -255,6 +255,13 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data 
*fsl_lpspi)
        u8 prescale;
 
        perclk_rate = clk_get_rate(fsl_lpspi->clk_per);
+
+       if (config.speed_hz > perclk_rate / 2) {
+               dev_err(fsl_lpspi->dev,
+                     "per-clk should be at least two times of transfer speed");
+               return -EINVAL;
+       }
+
        for (prescale = 0; prescale < 8; prescale++) {
                scldiv = perclk_rate /
                         (clkdivs[prescale] * config.speed_hz) - 2;
@@ -304,7 +311,7 @@ static int fsl_lpspi_config(struct fsl_lpspi_data 
*fsl_lpspi)
        return 0;
 }
 
-static void fsl_lpspi_setup_transfer(struct spi_device *spi,
+static int fsl_lpspi_setup_transfer(struct spi_device *spi,
                                     struct spi_transfer *t)
 {
        struct fsl_lpspi_data *fsl_lpspi =
@@ -337,7 +344,7 @@ static void fsl_lpspi_setup_transfer(struct spi_device *spi,
        else
                fsl_lpspi->watermark = fsl_lpspi->txfifosize;
 
-       fsl_lpspi_config(fsl_lpspi);
+       return fsl_lpspi_config(fsl_lpspi);
 }
 
 static int fsl_lpspi_slave_abort(struct spi_controller *controller)
@@ -429,7 +436,10 @@ static int fsl_lpspi_transfer_one_msg(struct 
spi_controller *controller,
        msg->actual_length = 0;
 
        list_for_each_entry(xfer, &msg->transfers, transfer_list) {
-               fsl_lpspi_setup_transfer(spi, xfer);
+               ret = fsl_lpspi_setup_transfer(spi, xfer);
+               if (ret < 0)
+                       goto complete;
+
                fsl_lpspi_set_cmd(fsl_lpspi, is_first_xfer);
 
                is_first_xfer = false;
-- 
2.17.1