mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

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>
This commit is contained in:
Alexandru M Stan 2015-06-09 13:04:49 +02:00 committed by Lee Jones
parent f44c21ff6d
commit ff4378f4b8
1 changed files with 19 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
drivers/mfd/cros_ec_spi.c
View File

@ -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;