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mfd: cros_ec: spi: Fix end of transfer on devices with no spi-msg-delay 

cros_ec_spi makes the assumption that a 0-length message will put the
spi chip select back to normal (non cs_toggle mode).  This used to be
the case back on kernel-3.8 on the spi-s3c64xx driver but doesn't
appear to be true anymore.  It seems like it was a pretty questionable
assumption to begin with, so let's fix the code to be more robust.  We
know that a message with a single 0-length segment _will_ put things
back in order.  Change cros_ec_spi to handle this.

This wasn't a problem on the main user of cros_ec_spi upstream (tegra)
because it specified 'google,cros-ec-spi-msg-delay'.

Signed-off-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
This commit is contained in:
Doug Anderson 2014-06-13 11:13:32 -07:00 committed by Lee Jones
parent c03842d89b
commit 967580598f
1 changed files with 7 additions and 11 deletions
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8
drivers/mfd/cros_ec_spi.c
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@ -266,18 +266,14 @@ static int cros_ec_command_spi_xfer(struct cros_ec_device *ec_dev,
dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret); dev_err(ec_dev->dev, "spi transfer failed: %d\n", ret);
} }
/* turn off CS */
spi_message_init(&msg);
if (ec_spi->end_of_msg_delay) {
/* /*
* Add delay for last transaction, to ensure the rising edge * Turn off CS, possibly adding a delay to ensure the rising edge
* doesn't come too soon after the end of the data. * doesn't come too soon after the end of the data.
*/ */
spi_message_init(&msg);
memset(&trans, 0, sizeof(trans)); memset(&trans, 0, sizeof(trans));
trans.delay_usecs = ec_spi->end_of_msg_delay; trans.delay_usecs = ec_spi->end_of_msg_delay;
spi_message_add_tail(&trans, &msg); spi_message_add_tail(&trans, &msg);
}
final_ret = spi_sync(ec_spi->spi, &msg); final_ret = spi_sync(ec_spi->spi, &msg);
ktime_get_ts(&ts); ktime_get_ts(&ts);