4.9-stable review patch. If anyone has any objections, please let me know.
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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 @@ -664,6 +664,7 @@ 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) {