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authorAlexandru M Stan <amstan@chromium.org>2015-06-09 13:04:49 +0200
committerLee Jones <lee.jones@linaro.org>2015-06-15 13:18:24 +0100
commitff4378f4b813d5aa26bbf814a9060638dab1fbbf (patch)
treec905a8f1116c051c51a48dabc347585632815332 /drivers/mfd
parentf44c21ff6d2dc76957ddbf26fdf442ee5a9cf3c0 (diff)
mfd: cros_ec: spi: Add delay for asserting CS
Some ECs need a little time for waking up before they can accept SPI data at a high speed. This is configurable via a DT property "google,cros-ec-spi-pre-delay". This patch makes the cros_ec_spi driver to cause a delay before the beginning of a SPI transaction, to make sure that the EC has already woken up, if the property has been defined in the DTS. Signed-off-by: Alexandru M Stan <amstan@chromium.org> Reviewed-by: Doug Anderson <dianders@chromium.org> Signed-off-by: Chris Zhong <zyw@rock-chips.com> Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk> Tested-by: Heiko Stuebner <heiko@sntech.de> Acked-by: Lee Jones <lee.jones@linaro.org> Acked-by: Olof Johansson <olof@lixom.net> Signed-off-by: Lee Jones <lee.jones@linaro.org>
Diffstat (limited to 'drivers/mfd')
-rw-r--r--drivers/mfd/cros_ec_spi.c21
1 files changed, 19 insertions, 2 deletions
diff --git a/drivers/mfd/cros_ec_spi.c b/drivers/mfd/cros_ec_spi.c
index faba03e2f1ef..16f228dc243f 100644
--- a/drivers/mfd/cros_ec_spi.c
+++ b/drivers/mfd/cros_ec_spi.c
@@ -71,12 +71,15 @@
* @spi: SPI device we are connected to
* @last_transfer_ns: time that we last finished a transfer, or 0 if there
* if no record
+ * @start_of_msg_delay: used to set the delay_usecs on the spi_transfer that
+ * is sent when we want to turn on CS at the start of a transaction.
* @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 start_of_msg_delay;
unsigned int end_of_msg_delay;
};
@@ -366,7 +369,7 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
struct ec_host_request *request;
struct ec_host_response *response;
struct cros_ec_spi *ec_spi = ec_dev->priv;
- struct spi_transfer trans;
+ struct spi_transfer trans, trans_delay;
struct spi_message msg;
int i, len;
u8 *ptr;
@@ -393,13 +396,23 @@ static int cros_ec_pkt_xfer_spi(struct cros_ec_device *ec_dev,
goto exit;
}
+ /*
+ * Leave a gap between CS assertion and clocking of data to allow the
+ * EC time to wakeup.
+ */
+ spi_message_init(&msg);
+ if (ec_spi->start_of_msg_delay) {
+ memset(&trans_delay, 0, sizeof(trans_delay));
+ trans_delay.delay_usecs = ec_spi->start_of_msg_delay;
+ spi_message_add_tail(&trans_delay, &msg);
+ }
+
/* Transmit phase - send our message */
memset(&trans, 0, sizeof(trans));
trans.tx_buf = ec_dev->dout;
trans.rx_buf = rx_buf;
trans.len = len;
trans.cs_change = 1;
- spi_message_init(&msg);
spi_message_add_tail(&trans, &msg);
ret = spi_sync(ec_spi->spi, &msg);
@@ -602,6 +615,10 @@ static void cros_ec_spi_dt_probe(struct cros_ec_spi *ec_spi, struct device *dev)
u32 val;
int ret;
+ ret = of_property_read_u32(np, "google,cros-ec-spi-pre-delay", &val);
+ if (!ret)
+ ec_spi->start_of_msg_delay = val;
+
ret = of_property_read_u32(np, "google,cros-ec-spi-msg-delay", &val);
if (!ret)
ec_spi->end_of_msg_delay = val;