From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750847AbdKSGKH (ORCPT ); Sun, 19 Nov 2017 01:10:07 -0500 Received: from mail-it0-f50.google.com ([209.85.214.50]:46605 "EHLO mail-it0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750744AbdKSGKD (ORCPT ); Sun, 19 Nov 2017 01:10:03 -0500 X-Google-Smtp-Source: AGs4zMYXpk1DbuNJsdmnL93naLBhyDZL39MdnD4szoI8qtS6/kPjxtAzaeekJVY9Cd9ZNiykLFH+gA== Date: Sat, 18 Nov 2017 22:09:58 -0800 From: Benson Leung To: Jon Hunter Cc: Lee Jones , linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org, Brian Norris , Shawn Nematbakhsh , Benson Leung , stable@vger.kernel.org Subject: Re: [PATCH V2 1/2] mfd: cros ec: spi: Don't send first message too soon Message-ID: <20171119060958.GA51565@decatoncale.mtv.corp.google.com> References: <1510670608-19594-1-git-send-email-jonathanh@nvidia.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="AhhlLboLdkugWU4S" Content-Disposition: inline In-Reply-To: <1510670608-19594-1-git-send-email-jonathanh@nvidia.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --AhhlLboLdkugWU4S Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi Jon, On Tue, Nov 14, 2017 at 02:43:27PM +0000, Jon Hunter wrote: > On the Tegra124 Nyan-Big chromebook the very first SPI message sent to > the EC is failing. >=20 > 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. >=20 > 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. >=20 > Cc: >=20 > Signed-off-by: Jon Hunter > Reviewed-by: Brian Norris Acked-by: Benson Leung --=20 Benson Leung Staff Software Engineer Chrome OS Kernel Google Inc. bleung@google.com Chromium OS Project bleung@chromium.org --AhhlLboLdkugWU4S Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJaESA2AAoJEB8J9XsKL+ZYeO4QAIfvZ7JvGyAAAyCii6ZnVaDk a808+u6i3WszujujcrtSgu3Y5PZpZHivyL+OFWhQ9VJaF6dJ+N3/vhewA/C9izgI P6Hu47XDNsdmj3t2185OpkZpe8p/HFScQmfN6dBasGX9GxKyxFksZPn953nJavAa k8DosACfQEAD27CHUDhvUyR28FNdmAGA0luk+rgwcBfpm9hnbXStopfGBN7IVSH1 jbqItD4+eqZGFxKz7U9Tj/TRnSbP3sUEL95xaegCAnK8eoWOBaAosl/SFiBb1/mZ 34NtEyxME+XCh6vlFv0Syfa2wcTrlUt0DlIWYIbnWnFGAJm1MuPbh03C1gip9Ikl mJ9RVSlwJl2lnzhI1z9pUvkq1+C22w/W5EzO3U/xjsjntNrorOz/oP5SZZ9ZLCUz zZAfaDkJR3gath/I7C0b4PnzG4CNUBAPrDGKD6/ZCgXSh4MokOsGu0yfzvU//u9i O30eCh/Cfd+0RJr5Zo7nd974+tX8NSo02AdhvgnuT/uCnF4dzvwa2Prq+ws4wfYQ xq+8u7QQoXA2bZcnfYU7dxb4QoM6Pk0Lvagv8Q8rPP3v5uxXGudUwAJxCN+OXikX v78KRsAXFViEUboO3cvwORXRDSfivslq0eHjzWKfYPbDa4TfkRfaTezJ2lOGGrDb oItmXpAf+ZjbQDdVAd+r =okKd -----END PGP SIGNATURE----- --AhhlLboLdkugWU4S--