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    Subject[PATCH 4.14 39/74] mfd: cros ec: spi: Dont send first message too soon
    Date
    4.14-stable 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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/mfd/cros_ec_spi.c | 1 +
    1 file changed, 1 insertion(+)

    --- a/drivers/mfd/cros_ec_spi.c
    +++ b/drivers/mfd/cros_ec_spi.c
    @@ -667,6 +667,7 @@ static int cros_ec_spi_probe(struct spi_
    sizeof(struct ec_response_get_protocol_info);
    ec_dev->dout_size = sizeof(struct ec_host_request);

    + ec_spi->last_transfer_ns = ktime_get_ns();

    err = cros_ec_register(ec_dev);
    if (err) {

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