4.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Jon Hunter <jonathanh@xxxxxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: Brian Norris <briannorris@xxxxxxxxxxxx>
Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Acked-by: Benson Leung <bleung@xxxxxxxxxxxx>
Signed-off-by: Lee Jones <lee.jones@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -660,6 +660,7 @@ 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) {