From mboxrd@z Thu Jan 1 00:00:00 1970 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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,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 491B4C35E0E for ; Tue, 25 Feb 2020 21:43:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 23DCA20675 for ; Tue, 25 Feb 2020 21:43:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729148AbgBYVnQ (ORCPT ); Tue, 25 Feb 2020 16:43:16 -0500 Received: from metis.ext.pengutronix.de ([85.220.165.71]:53419 "EHLO metis.ext.pengutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728756AbgBYVnP (ORCPT ); Tue, 25 Feb 2020 16:43:15 -0500 Received: from gallifrey.ext.pengutronix.de ([2001:67c:670:201:5054:ff:fe8d:eefb] helo=bjornoya.blackshift.org) by metis.ext.pengutronix.de with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1j6hyx-0004nE-BA; Tue, 25 Feb 2020 22:43:11 +0100 Received: from [IPv6:2a03:f580:87bc:d400:6ccf:3365:1a9c:55ad] (unknown [IPv6:2a03:f580:87bc:d400:6ccf:3365:1a9c:55ad]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (P-384) server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (4096 bits) client-digest SHA256) (Client CN "mkl@blackshift.org", Issuer "StartCom Class 1 Client CA" (not verified)) (Authenticated sender: mkl@blackshift.org) by smtp.blackshift.org (Postfix) with ESMTPSA id C8E924C0A43; Tue, 25 Feb 2020 21:43:09 +0000 (UTC) Subject: Re: [PATCH] can: mcp251x: convert to half-duplex SPI To: Tim Harvey , linux-kernel@vger.kernel.org, linux-can@vger.kernel.org, Wolfgang Grandegger Cc: =?UTF-8?Q?Timo_Schl=c3=bc=c3=9fler?= , Andy Shevchenko References: <1582655734-20890-1-git-send-email-tharvey@gateworks.com> From: Marc Kleine-Budde Openpgp: preference=signencrypt Autocrypt: addr=mkl@pengutronix.de; prefer-encrypt=mutual; keydata= mQINBFFVq30BEACtnSvtXHoeHJxG6nRULcvlkW6RuNwHKmrqoksispp43X8+nwqIFYgb8UaX zu8T6kZP2wEIpM9RjEL3jdBjZNCsjSS6x1qzpc2+2ivjdiJsqeaagIgvy2JWy7vUa4/PyGfx QyUeXOxdj59DvLwAx8I6hOgeHx2X/ntKAMUxwawYfPZpP3gwTNKc27dJWSomOLgp+gbmOmgc 6U5KwhAxPTEb3CsT5RicsC+uQQFumdl5I6XS+pbeXZndXwnj5t84M+HEj7RN6bUfV2WZO/AB Xt5+qFkC/AVUcj/dcHvZwQJlGeZxoi4veCoOT2MYqfR0ax1MmN+LVRvKm29oSyD4Ts/97cbs XsZDRxnEG3z/7Winiv0ZanclA7v7CQwrzsbpCv+oj+zokGuKasofzKdpywkjAfSE1zTyF+8K nxBAmzwEqeQ3iKqBc3AcCseqSPX53mPqmwvNVS2GqBpnOfY7Mxr1AEmxdEcRYbhG6Xdn+ACq Dq0Db3A++3PhMSaOu125uIAIwMXRJIzCXYSqXo8NIeo9tobk0C/9w3fUfMTrBDtSviLHqlp8 eQEP8+TDSmRP/CwmFHv36jd+XGmBHzW5I7qw0OORRwNFYBeEuiOIgxAfjjbLGHh9SRwEqXAL kw+WVTwh0MN1k7I9/CDVlGvc3yIKS0sA+wudYiselXzgLuP5cQARAQABtCZNYXJjIEtsZWlu ZS1CdWRkZSA8bWtsQHBlbmd1dHJvbml4LmRlPokCVAQTAQoAPgIbAwIeAQIXgAULCQgHAwUV CgkICwUWAgMBABYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJcUsSbBQkM366zAAoJECte4hHF iupUgkAP/2RdxKPZ3GMqag33jKwKAbn/fRqAFWqUH9TCsRH3h6+/uEPnZdzhkL4a9p/6OeJn Z6NXqgsyRAOTZsSFcwlfxLNHVxBWm8pMwrBecdt4lzrjSt/3ws2GqxPsmza1Gs61lEdYvLST Ix2vPbB4FAfE0kizKAjRZzlwOyuHOr2ilujDsKTpFtd8lV1nBNNn6HBIBR5ShvJnwyUdzuby tOsSt7qJEvF1x3y49bHCy3uy+MmYuoEyG6zo9udUzhVsKe3hHYC2kfB16ZOBjFC3lH2U5An+ yQYIIPZrSWXUeKjeMaKGvbg6W9Oi4XEtrwpzUGhbewxCZZCIrzAH2hz0dUhacxB201Y/faY6 BdTS75SPs+zjTYo8yE9Y9eG7x/lB60nQjJiZVNvZ88QDfVuLl/heuIq+fyNajBbqbtBT5CWf mOP4Dh4xjm3Vwlz8imWW/drEVJZJrPYqv0HdPbY8jVMpqoe5jDloyVn3prfLdXSbKPexlJaW 5tnPd4lj8rqOFShRnLFCibpeHWIumqrIqIkiRA9kFW3XMgtU6JkIrQzhJb6Tc6mZg2wuYW0d Wo2qvdziMgPkMFiWJpsxM9xPk9BBVwR+uojNq5LzdCsXQ2seG0dhaOTaaIDWVS8U/V8Nqjrl 6bGG2quo5YzJuXKjtKjZ4R6k762pHJ3tnzI/jnlc1sXz Message-ID: <0ac77abd-0df5-e437-ea46-f6c77f59b81c@pengutronix.de> Date: Tue, 25 Feb 2020 22:43:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <1582655734-20890-1-git-send-email-tharvey@gateworks.com> Content-Type: text/plain; charset=utf-8 Content-Language: de-DE Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-kernel@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/25/20 7:35 PM, Tim Harvey wrote: > Some SPI host controllers such as the Cavium Thunder do not support > full-duplex SPI. Using half-duplex transfers allows the driver to work > with those host controllers. There are several transfers left in the driver, where both rx_buf and tx_buf are set. How does your host controller driver know which one to handle? Marc > Signed-off-by: Tim Harvey > --- > drivers/net/can/spi/mcp251x.c | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/drivers/net/can/spi/mcp251x.c b/drivers/net/can/spi/mcp251x.c > index 5009ff2..840c31c 100644 > --- a/drivers/net/can/spi/mcp251x.c > +++ b/drivers/net/can/spi/mcp251x.c > @@ -290,23 +290,23 @@ static u8 mcp251x_read_reg(struct spi_device *spi, u8 reg) > priv->spi_tx_buf[0] = INSTRUCTION_READ; > priv->spi_tx_buf[1] = reg; > > - mcp251x_spi_trans(spi, 3); > - val = priv->spi_rx_buf[2]; > + spi_write_then_read(spi, priv->spi_tx_buf, 2, &val, 1); > > return val; > } > > static void mcp251x_read_2regs(struct spi_device *spi, u8 reg, u8 *v1, u8 *v2) > { > + u8 val[4] = {0}; > struct mcp251x_priv *priv = spi_get_drvdata(spi); > > priv->spi_tx_buf[0] = INSTRUCTION_READ; > priv->spi_tx_buf[1] = reg; > > - mcp251x_spi_trans(spi, 4); > + spi_write_then_read(spi, priv->spi_tx_buf, 2, val, 2); > > - *v1 = priv->spi_rx_buf[2]; > - *v2 = priv->spi_rx_buf[3]; > + *v1 = val[0]; > + *v2 = val[1]; > } > > static void mcp251x_write_reg(struct spi_device *spi, u8 reg, u8 val) > Marc -- Pengutronix e.K. | Marc Kleine-Budde | Embedded Linux | https://www.pengutronix.de | Vertretung West/Dortmund | Phone: +49-231-2826-924 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |