From patchwork Wed Dec 13 19:05:13 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Geert Uytterhoeven X-Patchwork-Id: 10110703 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 3956B60327 for ; Wed, 13 Dec 2017 19:05:33 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2C81E286DE for ; Wed, 13 Dec 2017 19:05:33 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 215F628701; Wed, 13 Dec 2017 19:05:33 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 16824286F4 for ; Wed, 13 Dec 2017 19:05:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753820AbdLMTFb (ORCPT ); Wed, 13 Dec 2017 14:05:31 -0500 Received: from baptiste.telenet-ops.be ([195.130.132.51]:35904 "EHLO baptiste.telenet-ops.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753729AbdLMTFW (ORCPT ); Wed, 13 Dec 2017 14:05:22 -0500 Received: from ayla.of.borg ([84.195.106.246]) by baptiste.telenet-ops.be with bizsmtp id lX5M1w00S5JzmfG01X5MXh; Wed, 13 Dec 2017 20:05:21 +0100 Received: from ramsan.of.borg ([192.168.97.29] helo=ramsan) by ayla.of.borg with esmtp (Exim 4.86_2) (envelope-from ) id 1ePCLJ-0006m4-Cb; Wed, 13 Dec 2017 20:05:21 +0100 Received: from geert by ramsan with local (Exim 4.86_2) (envelope-from ) id 1ePCLJ-0002mJ-9E; Wed, 13 Dec 2017 20:05:21 +0100 From: Geert Uytterhoeven To: Mark Brown , Rob Herring , Mark Rutland Cc: linux-spi@vger.kernel.org, devicetree@vger.kernel.org, linux-renesas-soc@vger.kernel.org, Geert Uytterhoeven Subject: [PATCH 4/4] spi: sh-msiof: Document hardware limitations related to chip selects Date: Wed, 13 Dec 2017 20:05:13 +0100 Message-Id: <1513191913-10612-5-git-send-email-geert+renesas@glider.be> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1513191913-10612-1-git-send-email-geert+renesas@glider.be> References: <1513191913-10612-1-git-send-email-geert+renesas@glider.be> Sender: linux-spi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Guide users to maintain the proper balance between native and GPIO chip selects. Signed-off-by: Geert Uytterhoeven --- Documentation/devicetree/bindings/spi/sh-msiof.txt | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/Documentation/devicetree/bindings/spi/sh-msiof.txt b/Documentation/devicetree/bindings/spi/sh-msiof.txt index bc8c16a6cfc82685..80710f0f04489174 100644 --- a/Documentation/devicetree/bindings/spi/sh-msiof.txt +++ b/Documentation/devicetree/bindings/spi/sh-msiof.txt @@ -41,6 +41,16 @@ Optional properties: 0: MSIOF_SYNC 1: MSIOF_SS1 2: MSIOF_SS2 + Hardware limitations related to chip selects: + - Native chip selects are always deasserted in + between transfers that are part of the same + message. Use cs-gpios to work around this. + - All slaves using native chip selects must use the + same spi-cs-high configuration. Use cs-gpios to + work around this. + - When using GPIO chip selects, at least one native + chip select must be left unused, as it will be + driven anyway. - dmas : Must contain a list of two references to DMA specifiers, one for transmission, and one for reception.