From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Jon Hunter , Brian Norris , Douglas Anderson , Benson Leung , Lee Jones Subject: [PATCH 4.9 04/21] mfd: cros ec: spi: Dont send first message too soon Date: Wed, 27 Dec 2017 17:46:20 +0100 Message-Id: <20171227164600.298288070@linuxfoundation.org> In-Reply-To: <20171227164559.973657621@linuxfoundation.org> References: <20171227164559.973657621@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Jon Hunter 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 Reviewed-by: Brian Norris Reviewed-by: Douglas Anderson Acked-by: Benson Leung Signed-off-by: Lee Jones Signed-off-by: Greg Kroah-Hartman --- 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) {