Commit ff4378f4 authored by Alexandru M Stan's avatar Alexandru M Stan Committed by Lee Jones
Browse files

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: default avatarAlexandru M Stan <amstan@chromium.org>
Reviewed-by: default avatarDoug Anderson <dianders@chromium.org>
Signed-off-by: default avatarChris Zhong <zyw@rock-chips.com>
Signed-off-by: default avatarJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: default avatarHeiko Stuebner <heiko@sntech.de>
Acked-by: default avatarLee Jones <lee.jones@linaro.org>
Acked-by: default avatarOlof Johansson <olof@lixom.net>
Signed-off-by: default avatarLee Jones <lee.jones@linaro.org>
parent f44c21ff

drivers/mfd/cros_ec_spi.c

+19 −2
Original line number Diff line number Diff line
@@ -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;

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