From patchwork Sat Dec 26 09:58:45 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ralf Schlatterbeck X-Patchwork-Id: 11990303 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7ECE1C433E0 for ; Sat, 26 Dec 2020 10:06:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3940D20791 for ; Sat, 26 Dec 2020 10:06:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725964AbgLZKFp (ORCPT ); Sat, 26 Dec 2020 05:05:45 -0500 Received: from tux.runtux.com ([176.9.82.136]:57772 "EHLO tux.runtux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725924AbgLZKFp (ORCPT ); Sat, 26 Dec 2020 05:05:45 -0500 X-Greylist: delayed 375 seconds by postgrey-1.27 at vger.kernel.org; Sat, 26 Dec 2020 05:05:44 EST Received: from localhost (localhost [127.0.0.1]) by tux.runtux.com (Postfix) with ESMTP id 262A86F070; Sat, 26 Dec 2020 10:58:48 +0100 (CET) X-Virus-Scanned: Debian amavisd-new at tux.runtux.com Received: from tux.runtux.com ([127.0.0.1]) by localhost (tux2.runtux.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id IXeIB_tByXV2; Sat, 26 Dec 2020 10:58:46 +0100 (CET) Received: from bee.priv.zoo (62-99-217-90.static.upcbusiness.at [62.99.217.90]) (Authenticated sender: postmaster@runtux.com) by tux.runtux.com (Postfix) with ESMTPSA id 81DFB6F01F; Sat, 26 Dec 2020 10:58:46 +0100 (CET) Received: by bee.priv.zoo (Postfix, from userid 1002) id 7505146C; Sat, 26 Dec 2020 10:58:45 +0100 (CET) Date: Sat, 26 Dec 2020 10:58:45 +0100 From: Ralf Schlatterbeck To: Mark Brown , Maxime Ripard , Chen-Yu Tsai , linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: [PATCH] Fix SPI Chipselect/Clock bug for sun6i Message-ID: <20201226095845.c65lhsmluddvwxsl@runtux.com> MIME-Version: 1.0 Content-Disposition: inline X-ray: beware User-Agent: NeoMutt/20180716 Precedence: bulk List-ID: X-Mailing-List: linux-spi@vger.kernel.org This patch makes additional GPIOs usable as chipselects for SPI. It is available for years on the linux-sunxi SPIdev page at http://linux-sunxi.org/SPIdev and probably is originally by the user "Mirko" there. I've tried unsuccessfully to contact the author. Note that contrary to what is stated on the page above, the bug doesn't have cosmetic implications only: The SPI-Driver for the H2 Allwinner processor in the Linux kernel is supposed to support normal GPIOs as additional chipselects but fails to do so without the patch. For oscilloscope screenshots with/without the patch, see my blog post https://blog.runtux.com/posts/2019/04/18/ or the discussion in the armbian forum at https://forum.armbian.com/topic/4330-spi-gpio-chip-select-support/ (my logo there is a penguin). Please bear with me if I'm not following proper procedures, this is my first patch to the kernel in years. Thanks Ralf Schlatterbeck From 682ae1848b0df00cceb4c76486b971826b2737a9 Mon Sep 17 00:00:00 2001 From: Ralf Schlatterbeck Date: Thu, 11 Apr 2019 16:21:54 +0200 Subject: [PATCH] Fix SPI Chipselect/Clock bug for sun6i Signed-off-by: Ralf Schlatterbeck The current sun6i SPI implementation initializes the transfer too early, resulting in SCK going high before the transer. When using an additional (gpio) chipselect with sun6i, the chipselect is asserted at a time when clock is high, making the SPI transfer fail. This patch from the sunxi spidev page http://linux-sunxi.org/SPIdev fixes this, without the patch no additional gpio chipselects can be used. The relevant code seems to be from the user "Mirko" of the linux-sunxi wiki page, I was unable to contact the original author. --- drivers/spi/spi-sun6i.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-) diff --git a/drivers/spi/spi-sun6i.c b/drivers/spi/spi-sun6i.c index 19238e1b76b4..9b292c6ade50 100644 --- a/drivers/spi/spi-sun6i.c +++ b/drivers/spi/spi-sun6i.c @@ -290,6 +290,10 @@ static int sun6i_spi_transfer_one(struct spi_master *master, } sun6i_spi_write(sspi, SUN6I_CLK_CTL_REG, reg); + /* Finally enable the bus - doing so before might raise SCK to HIGH */ + sun6i_spi_write(sspi, SUN6I_GBL_CTL_REG, + sun6i_spi_read(sspi, SUN6I_GBL_CTL_REG) + | SUN6I_GBL_CTL_BUS_ENABLE); /* Setup the transfer now... */ if (sspi->tx_buf) @@ -398,7 +402,7 @@ static int sun6i_spi_runtime_resume(struct device *dev) } sun6i_spi_write(sspi, SUN6I_GBL_CTL_REG, - SUN6I_GBL_CTL_BUS_ENABLE | SUN6I_GBL_CTL_MASTER | SUN6I_GBL_CTL_TP); + SUN6I_GBL_CTL_MASTER | SUN6I_GBL_CTL_TP); return 0;