From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Maciej W. Rozycki" Subject: Re: [PATCH] MIPS: Fix `dma_alloc_coherent' returning a non-coherent allocation Date: Thu, 1 Nov 2018 14:30:34 +0000 (GMT) Message-ID: References: <20180914095808.22202-1-hch@lst.de> <20180914095808.22202-5-hch@lst.de> <20181031203206.GA28337@lst.de> <20181101051359.GA4164@lst.de> <20181101083346.GA7136@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Return-path: In-Reply-To: <20181101083346.GA7136@lst.de> Sender: linux-kernel-owner@vger.kernel.org To: Christoph Hellwig Cc: Paul Burton , iommu@lists.linux-foundation.org, Marek Szyprowski , Robin Murphy , Greg Kroah-Hartman , linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org List-Id: iommu@lists.linux-foundation.org On Thu, 1 Nov 2018, Christoph Hellwig wrote: > Oops, yes this looks good: BTW, for anyone missing hardware suitable for serious DMA testing I can recommend getting a pair of DEFPA cards, the ubiquitous PCI version of this board, cheaply available, which is the same except for a different host bus bridge ASIC, developed later. They can be wired back to back similarly to Ethernet adapters (or in a loop if you have 2 or more dual attachment versions), no other hardware is required save for patch cords. Version 3 (DEFPA-xC) boards support universal PCI signalling, older ones are 5V-only. These devices are a stellar example of fine engineering[1]. Our `defxx' driver, which I believe has been adapted from the DEC OSF/1 one referred in the said document, has some latency and other issues that I plan to address sometime, once I have sorted higher-priority issues, however hardware itself is excellent. References: [1] Chran-Ham Chang et al., "High-performance TCP/IP and UDP/IP Networking in DEC OSF/1 for Alpha AXP", Digital Technical Journal, vol. 5, no. 1 (Winter 1993), "Network Adapter Characteristics", p. 7 Maciej