From patchwork Mon Jun 14 14:45:07 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ralf Schlatterbeck X-Patchwork-Id: 460097 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=-15.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, 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 C9A04C2B9F4 for ; Mon, 14 Jun 2021 14:45:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ADD026124B for ; Mon, 14 Jun 2021 14:45:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232805AbhFNOrS (ORCPT ); Mon, 14 Jun 2021 10:47:18 -0400 Received: from tux.runtux.com ([176.9.82.136]:41456 "EHLO tux.runtux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232798AbhFNOrR (ORCPT ); Mon, 14 Jun 2021 10:47:17 -0400 Received: from localhost (localhost [127.0.0.1]) by tux.runtux.com (Postfix) with ESMTP id 774556F033; Mon, 14 Jun 2021 16:45:11 +0200 (CEST) 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 LMTP id YZTLetKhIJS7; Mon, 14 Jun 2021 16:45:10 +0200 (CEST) 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 1454A6EF74; Mon, 14 Jun 2021 16:45:07 +0200 (CEST) Received: by bee.priv.zoo (Postfix, from userid 1002) id 7B97346E; Mon, 14 Jun 2021 16:45:07 +0200 (CEST) Date: Mon, 14 Jun 2021 16:45:07 +0200 From: Ralf Schlatterbeck To: Mark Brown , Maxime Ripard , Chen-Yu Tsai , Jernej Skrabec , linux-spi@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-sunxi@lists.linux.dev, linux-kernel@vger.kernel.org, Mirko Vogt Subject: [PATCH v2 1/1] spi: spi-sun6i: Fix chipselect/clock bug Message-ID: <20210614144507.y3udezjfbko7eavv@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 From: Mirko Vogt The current sun6i SPI implementation initializes the transfer too early, resulting in SCK going high before the transfer. 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 is due to SUN6I_GBL_CTL_BUS_ENABLE being written into SUN6I_GBL_CTL_REG at an early stage. Moving that to the transfer function, hence, right before the transfer starts, mitigates that problem. Fixes: 3558fe900e8af (spi: sunxi: Add Allwinner A31 SPI controller driver) Signed-off-by: Mirko Vogt Signed-off-by: Ralf Schlatterbeck --- 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). As far as we can tell the driver never worked with gpio chipselects. History: Updated patch with suggested readability-improvements by Andre Przywara 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 cc8401980125..23ad052528db 100644 --- a/drivers/spi/spi-sun6i.c +++ b/drivers/spi/spi-sun6i.c @@ -379,6 +379,10 @@ 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 */ + reg = sun6i_spi_read(sspi, SUN6I_GBL_CTL_REG); + reg |= SUN6I_GBL_CTL_BUS_ENABLE; + sun6i_spi_write(sspi, SUN6I_GBL_CTL_REG, reg); /* Setup the transfer now... */ if (sspi->tx_buf) @@ -504,7 +508,7 @@ 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;