fsl_dspi: Introduce DT bindings for CS-SCK and SCK-CS delays
Communication with some SPI slaves just won't cut it if these delays
(before the beginning, and after the end of a transfer) are not added to
the Chip Select signal.
These are a straight copy from Linux:
Documentation/devicetree/bindings/spi/spi-fsl-dspi.txt
drivers/spi/spi-fsl-dspi.c
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
[Rebased]
Signed-off-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/drivers/spi/fsl_dspi.c b/drivers/spi/fsl_dspi.c
index 78ad61ca..c55ebee 100644
--- a/drivers/spi/fsl_dspi.c
+++ b/drivers/spi/fsl_dspi.c
@@ -9,6 +9,7 @@
* Haikun Wang (B53464@freescale.com)
*/
+#include <linux/math64.h>
#include <common.h>
#include <dm.h>
#include <errno.h>
@@ -25,6 +26,9 @@
#include <linux/bitops.h>
#include <linux/delay.h>
+/* linux/include/time.h */
+#define NSEC_PER_SEC 1000000000L
+
DECLARE_GLOBAL_DATA_PTR;
/* fsl_dspi_platdata flags */
@@ -379,6 +383,40 @@
return -EINVAL;
}
+static void ns_delay_scale(unsigned char *psc, unsigned char *sc, int delay_ns,
+ unsigned long clkrate)
+{
+ int scale_needed, scale, minscale = INT_MAX;
+ int pscale_tbl[4] = {1, 3, 5, 7};
+ u32 remainder;
+ int i, j;
+
+ scale_needed = div_u64_rem((u64)delay_ns * clkrate, NSEC_PER_SEC,
+ &remainder);
+ if (remainder)
+ scale_needed++;
+
+ for (i = 0; i < ARRAY_SIZE(pscale_tbl); i++)
+ for (j = 0; j <= DSPI_CTAR_SCALE_BITS; j++) {
+ scale = pscale_tbl[i] * (2 << j);
+ if (scale >= scale_needed) {
+ if (scale < minscale) {
+ minscale = scale;
+ *psc = i;
+ *sc = j;
+ }
+ break;
+ }
+ }
+
+ if (minscale == INT_MAX) {
+ pr_warn("Cannot find correct scale values for %dns delay at clkrate %ld, using max prescaler value",
+ delay_ns, clkrate);
+ *psc = ARRAY_SIZE(pscale_tbl) - 1;
+ *sc = DSPI_CTAR_SCALE_BITS;
+ }
+}
+
static int fsl_dspi_cfg_speed(struct fsl_dspi_priv *priv, uint speed)
{
int ret;
@@ -412,6 +450,9 @@
{
struct dm_spi_slave_platdata *slave_plat = dev_get_parent_platdata(dev);
struct fsl_dspi_priv *priv = dev_get_priv(dev->parent);
+ u32 cs_sck_delay = 0, sck_cs_delay = 0;
+ unsigned char pcssck = 0, cssck = 0;
+ unsigned char pasc = 0, asc = 0;
if (slave_plat->cs >= priv->num_chipselect) {
debug("DSPI invalid chipselect number %d(max %d)!\n",
@@ -419,7 +460,18 @@
return -EINVAL;
}
- priv->ctar_val[slave_plat->cs] = DSPI_CTAR_DEFAULT_VALUE;
+ ofnode_read_u32(dev->node, "fsl,spi-cs-sck-delay", &cs_sck_delay);
+ ofnode_read_u32(dev->node, "fsl,spi-sck-cs-delay", &sck_cs_delay);
+
+ /* Set PCS to SCK delay scale values */
+ ns_delay_scale(&pcssck, &cssck, cs_sck_delay, priv->bus_clk);
+
+ /* Set After SCK delay scale values */
+ ns_delay_scale(&pasc, &asc, sck_cs_delay, priv->bus_clk);
+
+ priv->ctar_val[slave_plat->cs] = DSPI_CTAR_DEFAULT_VALUE |
+ DSPI_CTAR_PCSSCK(pcssck) |
+ DSPI_CTAR_PASC(pasc);
debug("DSPI pre_probe slave device on CS %u, max_hz %u, mode 0x%x.\n",
slave_plat->cs, slave_plat->max_hz, slave_plat->mode);