Re: What kind of Linux address must I use to set the SAR reg. of the DMA ctrl ?
From: Matt Porter <mporter@kernel.crashing.org>
Date: 2003-05-07 07:50:14
On Wed, May 07, 2003 at 02:52:06AM -0400, Callebaut Benoit wrote:
Hello, I am writing the code to start a DMA transfer with the built-in DMA controller of the MPC8245. The purpose is to do Memory to PCI transfers. The PCI part seems to be OK ( memory of the device is written) the the source address seems to be wrong since I read 0XFFFFFFFF as data in the device. I tried with bus and physical address (using virt_to_bus & virt_to_phys functions) but this doesn't give good results. So I ask myself which kind of linux address must I use to configure the SAR register of the Dual channel DMA controller ?
Well, there's no special "linux address". The DMA controller takes a physical address. I think you are specifically asking about configuring the source address register when doing a Mem->PCI transfer. In that case, if you are using lowmem system memory as the source address, then virt_to_phys will generate the correct physical system memory address. Regards, -- Matt Porter mporter@kernel.crashing.org ** Sent via the linuxppc-embedded mail list. See http://lists.linuxppc.org/