3.16.55-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Jon Hunter jonathanh@nvidia.com
commit 15d8374874ded0bec37ef27f8301a6d54032c0e5 upstream.
On the Tegra124 Nyan-Big chromebook the very first SPI message sent to the EC is failing.
The Tegra SPI driver configures the SPI chip-selects to be active-high by default (and always has for many years). The EC SPI requires an active-low chip-select and so the Tegra chip-select is reconfigured to be active-low when the EC SPI driver calls spi_setup(). The problem is that if the first SPI message to the EC is sent too soon after reconfiguring the SPI chip-select, it fails.
The EC SPI driver prevents back-to-back SPI messages being sent too soon by keeping track of the time the last transfer was sent via the variable 'last_transfer_ns'. To prevent the very first transfer being sent too soon, initialise the 'last_transfer_ns' variable after calling spi_setup() and before sending the first SPI message.
Signed-off-by: Jon Hunter jonathanh@nvidia.com Reviewed-by: Brian Norris briannorris@chromium.org Reviewed-by: Douglas Anderson dianders@chromium.org Acked-by: Benson Leung bleung@chromium.org Signed-off-by: Lee Jones lee.jones@linaro.org [bwh: Backported to 3.16: use ktime_get_ts() and timespec_to_ns()] Signed-off-by: Ben Hutchings ben@decadent.org.uk --- --- a/drivers/mfd/cros_ec_spi.c +++ b/drivers/mfd/cros_ec_spi.c @@ -347,6 +347,7 @@ static int cros_ec_spi_probe(struct spi_ struct device *dev = &spi->dev; struct cros_ec_device *ec_dev; struct cros_ec_spi *ec_spi; + struct timespec ts; int err;
spi->bits_per_word = 8; @@ -379,6 +380,9 @@ static int cros_ec_spi_probe(struct spi_ ec_dev->din_size = EC_MSG_BYTES + EC_MSG_PREAMBLE_COUNT; ec_dev->dout_size = EC_MSG_BYTES;
+ ktime_get_ts(&ts); + ec_spi->last_transfer_ns = timespec_to_ns(&ts); + err = cros_ec_register(ec_dev); if (err) { dev_err(dev, "cannot register EC\n");