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 C249DC433EF for ; Thu, 24 Mar 2022 13:30:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1350448AbiCXNbq (ORCPT ); Thu, 24 Mar 2022 09:31:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44476 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236979AbiCXNbo (ORCPT ); Thu, 24 Mar 2022 09:31:44 -0400 Received: from mail-pj1-x1029.google.com (mail-pj1-x1029.google.com [IPv6:2607:f8b0:4864:20::1029]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 717C766613 for ; Thu, 24 Mar 2022 06:30:12 -0700 (PDT) Received: by mail-pj1-x1029.google.com with SMTP id b8so4718495pjb.4 for ; Thu, 24 Mar 2022 06:30:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=Pg5zMHUoMOtfnb1TjqGEq+NoQ1459IJ3m+O0DUiruc0=; b=omvcrbN7lriPpSW5JaDifABkKoRy+47eDe5UOjgYcZYvGQlbPu6UX9LSEe8FXyZJsa iA4E7Y1dEpDv1TBqcgYb0x+NLebJXtHBP1M1Pcwa8JX29WOxvSReHn8/l0PVwcnvF430 59aicx9zgfahnRG9MD556r2AI1GFa1lRuBvga4UxFpm3SaxZJ6ERW+ZXis8i/PwMdIbb 02CFAatVGbDSo2MjvyGdNcdvX7Zu/dcFEHnuZJyddYEShRstLEZm6jwWWEi6M+VaOx3D 2UW+1n54RTfwPrZEn29ASdd7e8IPfJBCHfwiJBaSJz5tNddYOfSfiVtIOtS1CxFICfb2 InGg== 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=Pg5zMHUoMOtfnb1TjqGEq+NoQ1459IJ3m+O0DUiruc0=; b=3ITrUyxxJWsJ6Vatn9l3tZb8cOkHPaWL4bXf4mvHOKrIPcH4+4bPqTG7DKt2MpaP+5 pbbk+nYh9+dRg5v7hB5aTrL7AvW6PLdSR8JWuopzjWh6xszOLcigXCSYWfEQSJ6guKVu QtOo1h+n7Ig/l1yKR/03a+W1Va7M8Oqy/Sk2eR0HAKf0uBttp8jNvWjagjT4nAoGFdtt 5dtuJBYlQJI8W0fUSbeb+mVZDqO3zvoxMo/x/JWKbRnkMTMilNQJ84iY8r/SIXeMbE6O i71fxqatLivCt7k9s4wzhBh2EjT7O7A3WcFB39Wf6eMWNTDx8kiYuBI/JCC2yTIm8EIl wIFA== X-Gm-Message-State: AOAM531hPaj/PAzLge82NRx+VSXL84VU83gvPmM9KSA9C1sjEbxnxoEG U7gFMfLLxsSsOl26dh+ND4Wz X-Google-Smtp-Source: ABdhPJxo834+q44cy6Y/VdrbWR6viwcZl217ze+h8Xiz6Pw+AFEkkQShW97freIJEBaF33PZjpG9Xw== X-Received: by 2002:a17:902:8506:b0:154:8692:a7ac with SMTP id bj6-20020a170902850600b001548692a7acmr5896100plb.10.1648128611696; Thu, 24 Mar 2022 06:30:11 -0700 (PDT) Received: from thinkpad ([220.158.158.107]) by smtp.gmail.com with ESMTPSA id oa16-20020a17090b1bd000b001c72b632222sm10085543pjb.32.2022.03.24.06.30.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Mar 2022 06:30:11 -0700 (PDT) Date: Thu, 24 Mar 2022 19:00:04 +0530 From: Manivannan Sadhasivam To: Serge Semin Cc: Gustavo Pimentel , Vinod Koul , Jingoo Han , Bjorn Helgaas , Frank Li , Serge Semin , 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: <20220324133004.GM2854@thinkpad> References: <20220324014836.19149-1-Sergey.Semin@baikalelectronics.ru> <20220324014836.19149-2-Sergey.Semin@baikalelectronics.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220324014836.19149-2-Sergey.Semin@baikalelectronics.ru> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org 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. 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 >