mfd: cros ec: spi: Add delay for raising CS
The EC has specific timing it requires. Add support for an optional delay
after raising CS to fix timing issues. This is configurable based on
a DT property "google,cros-ec-spi-msg-delay".
If this property isn't set, then no delay will be added. However, if set
it will cause a delay equal to the value passed to it to be inserted at
the end of a transaction.
Signed-off-by: Rhyland Klein <rklein@nvidia.com>
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
Reviewed-by: Andrew Bresticker <abrestic@chromium.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index 0054036..84af8d7 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -18,6 +18,7 @@
#include <linux/module.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
+#include <linux/of.h>
#include <linux/platform_device.h>
#include <linux/slab.h>
#include <linux/spi/spi.h>
@@ -62,10 +63,13 @@
* @spi: SPI device we are connected to
* @last_transfer_ns: time that we last finished a transfer, or 0 if there
* if no record
+ * @end_of_msg_delay: used to set the delay_usecs on the spi_transfer that
+ * is sent when we want to turn off CS at the end of a transaction.
*/
struct cros_ec_spi {
struct spi_device *spi;
s64 last_transfer_ns;
+ unsigned int end_of_msg_delay;
};
static void debug_packet(struct device *dev, const char *name, u8 *ptr,
@@ -238,6 +242,17 @@
/* turn off CS */
spi_message_init(&msg);
+
+ if (ec_spi->end_of_msg_delay) {
+ /*
+ * Add delay for last transaction, to ensure the rising edge
+ * doesn't come too soon after the end of the data.
+ */
+ memset(&trans, 0, sizeof(trans));
+ trans.delay_usecs = ec_spi->end_of_msg_delay;
+ spi_message_add_tail(&trans, &msg);
+ }
+
final_ret = spi_sync(ec_spi->spi, &msg);
ktime_get_ts(&ts);
ec_spi->last_transfer_ns = timespec_to_ns(&ts);
@@ -284,6 +299,17 @@
return 0;
}
+static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
+{
+ struct device_node *np = dev->of_node;
+ u32 val;
+ int ret;
+
+ ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
+ if (!ret)
+ ec_spi->end_of_msg_delay = val;
+}
+
static int cros_ec_spi_probe(struct spi_device *spi)
{
struct device *dev = &spi->dev;
@@ -305,6 +331,9 @@
if (!ec_dev)
return -ENOMEM;
+ /* Check for any DT properties */
+ cros_ec_spi_dt_probe(ec_spi, dev);
+
spi_set_drvdata(spi, ec_dev);
ec_dev->name = "SPI";
ec_dev->dev = dev;