drivers: spi_nxp_lpspi: Don't fetch clockrate from api during configure

The clock get rate api can be slow in certain targets and thus slowing
each SPI transaction. Instead on startup fetch the clock rate and store
this in ram. Then each spi configure action is simply reading that
variable

Signed-off-by: Peter van der Perk <peter.vanderperk@nxp.com>

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi_common.c

@@ -260,7 +260,6 @@ static void lpspi_basic_config(const struct device *dev, const struct spi_config
 
 int lpspi_configure(const struct device *dev, const struct spi_config *spi_cfg)
 {
-	const struct lpspi_config *config = dev->config;
 	struct lpspi_data *data = dev->data;
 	struct spi_context *ctx = &data->ctx;
 	bool already_configured = spi_context_configured(ctx, spi_cfg);
@@ -306,10 +305,7 @@ int lpspi_configure(const struct device *dev, const struct spi_config *spi_cfg)
 
 	lpspi_basic_config(dev, spi_cfg);
 
-	ret = clock_control_get_rate(config->clock_dev, config->clock_subsys, &clock_freq);
-	if (ret) {
-		return ret;
-	}
+	clock_freq = data->clock_freq;
 
 	if (SPI_OP_MODE_GET(spi_cfg->operation) == SPI_OP_MODE_MASTER) {
 		uint32_t ccr = 0;
@@ -374,6 +370,11 @@ int spi_nxp_init_common(const struct device *dev)
 		return err;
 	}
 
+	err = clock_control_get_rate(config->clock_dev, config->clock_subsys, &data->clock_freq);
+	if (err) {
+		return err;
+	}
+
 	/* Full software reset */
 	base->CR |= LPSPI_CR_RST_MASK;
 	base->CR |= LPSPI_CR_RRF_MASK | LPSPI_CR_RTF_MASK;

drivers/spi/spi_nxp_lpspi/spi_nxp_lpspi_priv.h

@@ -51,6 +51,7 @@ struct lpspi_data {
 	void *driver_data;
 	size_t transfer_len;
 	uint8_t major_version;
+	uint32_t clock_freq;
 };
 
 /* Verifies spi_cfg validity and set up configuration of hardware for xfer