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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id C33CEC47080 for ; Wed, 6 Apr 2022 02:02:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1845862AbiDFCBk (ORCPT ); Tue, 5 Apr 2022 22:01:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46060 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356447AbiDELze (ORCPT ); Tue, 5 Apr 2022 07:55:34 -0400 Received: from mail-lj1-x235.google.com (mail-lj1-x235.google.com [IPv6:2a00:1450:4864:20::235]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8C2D31034; Tue, 5 Apr 2022 04:15:42 -0700 (PDT) Received: by mail-lj1-x235.google.com with SMTP id b43so16586854ljr.10; Tue, 05 Apr 2022 04:15:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=KKe+mIlQBUIwvKVa06G3uVTMkCxHX4Htb5pg4RZxzhg=; b=ABQNLW/vYg5pYwMyN5PJmiwoIgtn/341GnSMHpr8eM1wWv71qL84BUvIqpRjesuXQ7 KhkcHoiCFKYUzdoD9VbzOjGd3OLbpUBq32kRpvO9csu2LR0KLF2Slh3eSY2IAoNH/0Es xu69KfygMVU6oCHFQSuzwPlFtnM0Kzc5kamXFpsDpWopdejjIleUu7XXdEHAojgAgawd BF1MhWkCOV3gE6sUeEwDDRP6MPoBOJcgQdNDlhOP5WwMdrcNc6DL8x7dfo3KEQlbc5r5 bCcA2crvKwe/9uPLyBKoo52sJb4Y5TlHeNC37vj8dlS41p1WeHUec+5eXX2Zf60yxZmh H9wQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=KKe+mIlQBUIwvKVa06G3uVTMkCxHX4Htb5pg4RZxzhg=; b=43JibDKwqSldk/L5xfjs2AP4ziEGr1+75md3/vx4ECddvcGUuxrn4jECgdRZssyX2A YluAPObaf4EIIoufStVT6Z5/TMc/9wHlK3FPrWwQeRmvuPY5bUKGy2QNRqaowGRLNFPz b9Mb0qOqdupjrw+5/Hp5jKwMxpfjVKRvjtkX808mzLji9oLTz12rKqeqbNjAjeDNo7Os rEZuigQ5CLJNFsQOw0G/6PrS3O5lIcoIobr6cLSXZqYL39l2xkfaZVks25/TPc2+d9JR C+TT4b6vnbj/s3xPupzeqB0CXGXf+vjxmGd0FPVlLbrju4WAEAPcH4NTXKo12tNqf5zg mrWA== X-Gm-Message-State: AOAM532VrnSAtSDR6A+JzVfZzis7icco6Sj6MTquVxgPH5dNrszqHU2Y Y6H5qWWZvi0co8Hm1+T0NjU= X-Google-Smtp-Source: ABdhPJxSh27o37jD1zZo2k4S0Jf7NO6/98sGHWML8ZRw8+dIWO7pLj3iaVua1piJgAhMIorCsArSYw== X-Received: by 2002:a2e:9f47:0:b0:24b:12a9:36dd with SMTP id v7-20020a2e9f47000000b0024b12a936ddmr1767594ljk.509.1649157340680; Tue, 05 Apr 2022 04:15:40 -0700 (PDT) Received: from mobilestation ([85.249.23.165]) by smtp.gmail.com with ESMTPSA id r23-20020a2e94d7000000b0024b1565bba8sm717942ljh.118.2022.04.05.04.15.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Apr 2022 04:15:39 -0700 (PDT) Date: Tue, 5 Apr 2022 14:15:37 +0300 From: Serge Semin To: Manivannan Sadhasivam Cc: Serge Semin , Gustavo Pimentel , Vinod Koul , Jingoo Han , Bjorn Helgaas , Frank Li , Alexey Malahov , Pavel Parkhomenko , Lorenzo Pieralisi , Rob Herring , Krzysztof =?utf-8?Q?Wilczy=C5=84ski?= , linux-pci@vger.kernel.org, dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 01/25] dmaengine: dw-edma: Drop dma_slave_config.direction field usage Message-ID: <20220405111537.5g6izfutmx5e4gkj@mobilestation> References: <20220324014836.19149-1-Sergey.Semin@baikalelectronics.ru> <20220324014836.19149-2-Sergey.Semin@baikalelectronics.ru> <20220324133004.GM2854@thinkpad> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324133004.GM2854@thinkpad> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 24, 2022 at 07:00:04PM +0530, Manivannan Sadhasivam wrote: > On Thu, Mar 24, 2022 at 04:48:12AM +0300, Serge Semin wrote: > > The dma_slave_config.direction field usage in the DW eDMA driver has been > > introduced in the commit bd96f1b2f43a ("dmaengine: dw-edma: support local > > dma device transfer semantics"). Mainly the change introduced there was > > correct (indeed DEV_TO_MEM means using RD-channel and MEM_TO_DEV - > > WR-channel for the case of having eDMA accessed locally from > > CPU/Application side), but providing an additional > > MEM_TO_MEM/DEV_TO_DEV-based semantics was quite redundant if not to say > > potentially harmful (when it comes to removing the denoted field). First > > of all since the dma_slave_config.direction field has been marked as > > obsolete (see [1] and the structure dc [2]) and will be discarded in > > future, using it especially in a non-standard way is discouraged. Secondly > > in accordance with the commit denoted above the default > > dw_edma_device_transfer() semantics has been changed despite what it's > > message said. So claiming that the method was left backward compatible was > > wrong. > > > > Anyway let's fix the problems denoted above and simplify the > > dw_edma_device_transfer() method by dropping the parsing of the > > DMA-channel direction field. Instead of having that implicit > > dma_slave_config.direction field semantic we can use the recently added > > DW_EDMA_CHIP_LOCAL flag to distinguish between the local and remote DW > > eDMA setups thus preserving both cases support. In addition to that an > > ASCII-figure has been added to clarify the complication out. > > > > [1] Documentation/driver-api/dmaengine/provider.rst > > [2] include/linux/dmaengine.h: dma_slave_config.direction > > > > Co-developed-by: Manivannan Sadhasivam > > Signed-off-by: Manivannan Sadhasivam > > Signed-off-by: Serge Semin > > > > --- > > > > In accordance with agreement with Frank and Manivannan this patch is > > supposed to be moved to the series: > > Link: https://lore.kernel.org/dmaengine/20220310192457.3090-1-Frank.Li@nxp.com/ > > in place of the patch: > > [PATCH v5 6/9] dmaengine: dw-edma: Don't rely on the deprecated "direction" member > > Link: https://lore.kernel.org/dmaengine/20220310192457.3090-7-Frank.Li@nxp.com/ > > --- > > drivers/dma/dw-edma/dw-edma-core.c | 49 +++++++++++++++++++++--------- > > 1 file changed, 34 insertions(+), 15 deletions(-) > > > > diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c > > index 5be8a5944714..e9e32ed74aa9 100644 > > --- a/drivers/dma/dw-edma/dw-edma-core.c > > +++ b/drivers/dma/dw-edma/dw-edma-core.c > > @@ -339,21 +339,40 @@ dw_edma_device_transfer(struct dw_edma_transfer *xfer) > > if (!chan->configured) > > return NULL; > > > > - switch (chan->config.direction) { > > - case DMA_DEV_TO_MEM: /* local DMA */ > > - if (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_READ) > > - break; > > - return NULL; > > - case DMA_MEM_TO_DEV: /* local DMA */ > > - if (dir == DMA_MEM_TO_DEV && chan->dir == EDMA_DIR_WRITE) > > - break; > > - return NULL; > > - default: /* remote DMA */ > > - if (dir == DMA_MEM_TO_DEV && chan->dir == EDMA_DIR_READ) > > - break; > > - if (dir == DMA_DEV_TO_MEM && chan->dir == EDMA_DIR_WRITE) > > - break; > > - return NULL; > > + /* > > + * Local Root Port/End-point Remote End-point > > + * +-----------------------+ PCIe bus +----------------------+ > > + * | | +-+ | | > > + * | DEV_TO_MEM Rx Ch <----+ +---+ Tx Ch DEV_TO_MEM | > > + * | | | | | | > > + * | MEM_TO_DEV Tx Ch +----+ +---> Rx Ch MEM_TO_DEV | > > + * | | +-+ | | > > + * +-----------------------+ +----------------------+ > > + * > > + * 1. Normal logic: > > + * If eDMA is embedded into the DW PCIe RP/EP and controlled from the > > + * CPU/Application side, the Rx channel (EDMA_DIR_READ) will be used > > + * for the device read operations (DEV_TO_MEM) and the Tx channel > > + * (EDMA_DIR_WRITE) - for the write operations (MEM_TO_DEV). > > + * > > + * 2. Inverted logic: > > + * If eDMA is embedded into a Remote PCIe EP and is controlled by the > > + * MWr/MRd TLPs sent from the CPU's PCIe host controller, the Tx > > + * channel (EDMA_DIR_WRITE) will be used for the device read operations > > + * (DEV_TO_MEM) and the Rx channel (EDMA_DIR_READ) - for the write > > + * operations (MEM_TO_DEV). > > + * > > + * It is the client driver responsibility to choose a proper channel > > + * for the DMA transfers. > > + */ > > I think it'd be good to document this using some form in "enum dw_edma_dir" > declaration. Well, I'd rather leave the comment here. The dw_edma_dir enumeration only defines the actual device channel direction, while the actual semantics is determined by the PCIe device residence/configuration (local + host/end-point, remote + end-point) and is reflected in the data transfer function - dw_edma_device_transfer(). So as I see it the comment is more suitable to be left here in the place where the semantic is actually implemented. -Sergey > > Thanks, > Mani > > > + if (chan->dw->chip->flags & DW_EDMA_CHIP_LOCAL) { > > + if ((chan->dir == EDMA_DIR_READ && dir != DMA_DEV_TO_MEM) || > > + (chan->dir == EDMA_DIR_WRITE && dir != DMA_MEM_TO_DEV)) > > + return NULL; > > + } else { > > + if ((chan->dir == EDMA_DIR_WRITE && dir != DMA_DEV_TO_MEM) || > > + (chan->dir == EDMA_DIR_READ && dir != DMA_MEM_TO_DEV)) > > + return NULL; > > } > > > > if (xfer->type == EDMA_XFER_CYCLIC) { > > -- > > 2.35.1 > >