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=-10.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,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 36701C4321A for ; Fri, 28 Jun 2019 19:00:27 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1786120828 for ; Fri, 28 Jun 2019 19:00:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726908AbfF1TA0 (ORCPT ); Fri, 28 Jun 2019 15:00:26 -0400 Received: from bmailout2.hostsharing.net ([83.223.90.240]:36543 "EHLO bmailout2.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726565AbfF1TAZ (ORCPT ); Fri, 28 Jun 2019 15:00:25 -0400 Received: from h08.hostsharing.net (h08.hostsharing.net [83.223.95.28]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (not verified)) by bmailout2.hostsharing.net (Postfix) with ESMTPS id 3B9872800BC1C; Fri, 28 Jun 2019 21:00:23 +0200 (CEST) Received: by h08.hostsharing.net (Postfix, from userid 100393) id D2E9316F24; Fri, 28 Jun 2019 21:00:22 +0200 (CEST) Date: Fri, 28 Jun 2019 21:00:22 +0200 From: Lukas Wunner To: Stefan Wahren Cc: Nuno =?iso-8859-1?Q?S=E1?= , broonie@kernel.org, eric@anholt.net, Martin Sperl , f.fainelli@gmail.com, rjui@broadcom.com, sbranden@broadcom.com, linux-kernel@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com, linux-rpi-kernel@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-spi@vger.kernel.org Subject: Re: [PATCH] spi: spi-bcm2835.c: Fix 3-wire mode Message-ID: <20190628190022.vya4h2lihm6x2xpb@wunner.de> References: <20190628123023.4696-1-nuno.sa@analog.com> <1b932c61-982b-aae0-1fef-3c574e7d17eb@gmx.net> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1b932c61-982b-aae0-1fef-3c574e7d17eb@gmx.net> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 28, 2019 at 05:23:54PM +0200, Stefan Wahren wrote: > Am 28.06.19 um 14:30 schrieb Nuno Sá: > > As stated in > > https://www.raspberrypi.org/documentation/hardware/raspberrypi/spi/README.md, > > one of rx or tx buffer's must be null. However, if DMA is enabled, the > > driver sets the SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX on the > > controller flags. Hence, the spi core will provide dummy buffers even if > > one of the buffers was set to null by the device driver. Thus, the > > communication with the 3-wire device fails. > > > > This patch uses the prepare_message callback to look for the device mode > > and sets/clears the SPI_CONTROLLER_MUST_RX | SPI_CONTROLLER_MUST_TX on a > > per spi message basis. It also assumes that DMA is not supported on > > half-duplex devices. > > > > Signed-off-by: Nuno Sá > > i never tested the 3-wire mode. Could you please describe your test setup? __spi_validate() returns -EINVAL if 3-wire mode is used and both buffers are non-NULL, I guess that's the problem. > @Martin, @Lukas Are you fine with this patch? I have a patch set in the pipeline to drop SPI_CONTROLLER_MUST_RX and SPI_CONTROLLER_MUST_TX from spi-bcm2835.c. Latest snapshot is available here (top-most 10 commits): https://github.com/l1k/linux/commits/revpi_staging @Nuno, could you give this branch a spin and see if it fixes the issue for you? If so, this might be a better solution. Your patch is fine in principle since it works around the problem, but the patch set on the above-linked branch fixes it at the root. It also provides a nice welcome speedup and reduces resource consumption. I've been working on this on-and-off for about half a year, I think the patch set is in pretty good shape now so I was planning to submit it probably in 2 weeks or so. Thanks, Lukas