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 3.18-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
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-3.18 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 15d8374874ded0bec37ef27f8301a6d54032c0e5 Mon Sep 17 00:00:00 2001
From: Jon Hunter <jonathanh@xxxxxxxxxx>
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@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
@@ -23,6 +23,7 @@
#include <linux/slab.h>
#include <linux/spi/spi.h>
+ ec_spi->last_transfer_ns = ktime_get_ns();
/* The header byte, which follows the preamble */
#define EC_MSG_HEADER 0xec
Patches currently in stable-queue which might be from jonathanh@xxxxxxxxxx are
queue-3.18/mfd-cros-ec-spi-don-t-send-first-message-too-soon.patch