On Mon, Jan 27, 2014 at 04:13:56PM +0100, Guennadi Liakhovetski wrote: > I'm working on an MMC driver with a DMA capability. All has been working > well, until at some point I've got a bus error, when the mmc driver had > been handed in a buffer at 0x3000 physical RAM address. The reason is, > that on Zynq arch bus masters cannot access RAM below 0x80000. Therefore > my question: how shall I configure this in software? You're going to run into all sorts of problems here. Normally, the DMA-able memory is limited to the first N bytes of memory, not "you must avoid the first N bytes of memory". Linux has it hard-coded into the memory subsystems that the DMA zone is from the start of memory to N, the normal zone is from N to H, and high memory is from H upwards - and allocations for high can fall back to normal, which can fall back to DMA but not the other way around. Short of permanently reserving the first 0x80000 bytes of memory, I'm not sure that there's much which can be done. You may wish to talk to the MM gurus to see whether there's a modern alternative. -- FTTC broadband for 0.8mile line: 5.8Mbps down 500kbps up. Estimation in database were 13.1 to 19Mbit for a good line, about 7.5+ for a bad. Estimate before purchase was "up to 13.2Mbit". -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
