spi: spi-fsl-lpspi: Some calculation improvements

Merge series from Stefan Wahren <wahrenst@gmx.net>:

This series contains some improvements for spi-fsl-lpspi which are
related to the calculations within fsl_lpspi_set_bitrate.

Author: broonie

drivers/spi/spi-fsl-lpspi.c

@@ -92,6 +92,7 @@ struct lpspi_config {
 	u8 prescale;
 	u16 mode;
 	u32 speed_hz;
+	u32 effective_speed_hz;
 };
 
 struct fsl_lpspi_data {
@@ -315,9 +316,10 @@ static void fsl_lpspi_set_watermark(struct fsl_lpspi_data *fsl_lpspi)
 static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
 {
 	struct lpspi_config config = fsl_lpspi->config;
-	unsigned int perclk_rate, scldiv, div;
+	unsigned int perclk_rate, div;
 	u8 prescale_max;
 	u8 prescale;
+	int scldiv;
 
 	perclk_rate = clk_get_rate(fsl_lpspi->clk_per);
 	prescale_max = fsl_lpspi->devtype_data->prescale_max;
@@ -338,19 +340,22 @@ static int fsl_lpspi_set_bitrate(struct fsl_lpspi_data *fsl_lpspi)
 
 	for (prescale = 0; prescale <= prescale_max; prescale++) {
 		scldiv = div / (1 << prescale) - 2;
-		if (scldiv < 256) {
+		if (scldiv >= 0 && scldiv < 256) {
 			fsl_lpspi->config.prescale = prescale;
 			break;
 		}
 	}
 
-	if (scldiv >= 256)
+	if (scldiv < 0 || scldiv >= 256)
 		return -EINVAL;
 
 	writel(scldiv | (scldiv << 8) | ((scldiv >> 1) << 16),
 					fsl_lpspi->base + IMX7ULP_CCR);
 
-	dev_dbg(fsl_lpspi->dev, "perclk=%d, speed=%d, prescale=%d, scldiv=%d\n",
+	fsl_lpspi->config.effective_speed_hz = perclk_rate / (scldiv + 2) *
+					       (1 << prescale);
+
+	dev_dbg(fsl_lpspi->dev, "perclk=%u, speed=%u, prescale=%u, scldiv=%d\n",
 		perclk_rate, config.speed_hz, prescale, scldiv);
 
 	return 0;
@@ -749,6 +754,8 @@ static int fsl_lpspi_transfer_one(struct spi_controller *controller,
 	if (ret < 0)
 		return ret;
 
+	t->effective_speed_hz = fsl_lpspi->config.effective_speed_hz;
+
 	fsl_lpspi_set_cmd(fsl_lpspi);
 	fsl_lpspi->is_first_byte = false;