From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from tux.runtux.com (tux.runtux.com [176.9.82.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 167A470 for ; Fri, 21 May 2021 20:19:17 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by tux.runtux.com (Postfix) with ESMTP id DE1E96F00A; Fri, 21 May 2021 22:19:15 +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 idEQAUquvFTc; Fri, 21 May 2021 22:19:14 +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 EBA096EF63; Fri, 21 May 2021 22:19:13 +0200 (CEST) Received: by bee.priv.zoo (Postfix, from userid 1002) id 9233046E; Fri, 21 May 2021 22:19:13 +0200 (CEST) Date: Fri, 21 May 2021 22:19:13 +0200 From: Ralf Schlatterbeck To: Andre Przywara Cc: 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 1/1] spi-sun6i: Fix chipselect/clock bug Message-ID: <20210521201913.2gapcmrzynxekro7@runtux.com> References: <20210520100656.rgkdexdvrddt3upy@runtux.com> <20210521173011.1c602682@slackpad.fritz.box> X-Mailing-List: linux-sunxi@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210521173011.1c602682@slackpad.fritz.box> X-ray: beware User-Agent: NeoMutt/20180716 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. Signed-off-by: Mirko Vogt Signed-off-by: Ralf Schlatterbeck --- Updated patch with suggested improvements by Andre Przywara 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). 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; -- 2.20.1