This is a note to let you know that I've just added the patch titled

mfd: cros ec: spi: Don't send first message too soon

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mfd-cros-ec-spi-don-t-send-first-message-too-soon.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 15d8374874ded0bec37ef27f8301a6d54032c0e5 Mon Sep 17 00:00:00 2001

From: Jon Hunter jonathanh@nvidia.com Date: Tue, 14 Nov 2017 14:43:27 +0000 Subject: mfd: cros ec: spi: Don't send first message too soon

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 @@ -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) {

Patches currently in stable-queue which might be from jonathanh@nvidia.com are

queue-4.4/mfd-cros-ec-spi-don-t-send-first-message-too-soon.patch