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authorRhyland Klein <rklein@nvidia.com>2013-12-09 12:36:09 +0100
committerLee Jones <lee.jones@linaro.org>2014-01-21 08:28:06 +0000
commit01e73c89cf03c020e586dc9e30d52a6e098853f6 (patch)
treedaef78c50110f4fed3218742bf8c6560e3645639 /drivers
parentdaf93d2287ff8eb4a2f28224275fb02d623df2ab (diff)
downloadlinux-01e73c89cf03c020e586dc9e30d52a6e098853f6.tar.bz2
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>
Diffstat (limited to 'drivers')
-rw-r--r--drivers/mfd/cros_ec_spi.c29
1 files changed, 29 insertions, 0 deletions
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index 005403643539..84af8d7a4295 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 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
/* 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 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
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 @@ static int cros_ec_spi_probe(struct spi_device *spi)
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;