From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from az33egw02.freescale.net (az33egw02.freescale.net [192.88.158.103]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "az33egw02.freescale.net", Issuer "Thawte Premium Server CA" (verified OK)) by ozlabs.org (Postfix) with ESMTPS id 98740DDDA2 for ; Tue, 28 Apr 2009 06:26:44 +1000 (EST) Message-ID: <49F614FC.70000@freescale.com> Date: Mon, 27 Apr 2009 15:26:36 -0500 From: Timur Tabi MIME-Version: 1.0 To: David Hawkins Subject: Re: [PATCH] fsldma: use PCI Read Multiple command References: <20090424183517.GB23140@ovro.caltech.edu> <49F608B7.9080409@ovro.caltech.edu> <49F60A3A.4060402@freescale.com> <49F61416.8040501@ovro.caltech.edu> In-Reply-To: <49F61416.8040501@ovro.caltech.edu> Content-Type: text/plain; charset=ISO-8859-1 Cc: linuxppc-dev@ozlabs.org, Dan Williams , Liu Dave-R63238 , linux-kernel@vger.kernel.org, Ira Snyder List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , David Hawkins wrote: > PRC_RM - PCI read multiple > The default PCI read command used by the DMA controller is > PCI Read (PCI command 6h). When the burst length is 32-bytes > or longer, PCI Read Line (PCI command Eh) is used (undocumented > feature of the controller). Using PCI read multiple > (PCI command Ch) results in high-performance across PCI > bridges. DMA transfers to non-prefetchable PCI registers > should not result in prefetched reads, even when using > the PCI read multiple command. I was thinking more along the lines of: "This driver tells the DMA controller to use the PCI Read Multiple command, instead of the PCI Read Line command, for PCI read operations. Please be aware that this setting may result in read pre-fetching on some platforms." -- Timur Tabi Linux kernel developer at Freescale