Hello, I'm trying to put a Blade 150 to use. I installed two 160 GB UDMA drives to replace the 40 GB Seagate drive the machine shipped with. Unfortunately, the Blade 150 uses the ALI (Acer) M5229 series ATA controller chip, which (at least for the revs on these Suns) can't do DMA simultaneously with LBA48 addressing.
In src/sys/dev/pci/pciide.c the acer_dma_init function seems to handle this by checking to see if the LBA48 flag is turned on, and if so, returning EINVAL , resulting in PIO transfers only for the disk. I would much rather use DMA with some loss of capacity than use PIO, particularly with the disks I have (it wouldn't be much capacity lost). See also the thread at: http://marc.info/?l=freebsd-current&m=112404856418435&w=2 (Q1): Is there a way to tell the wd or pciide drivers to not use LBA48 even if the drive supports it? Looking through the sources, I don't think there is, but I thought I'd ask to be sure. (Q2): Assuming there is not a provided way to turn off LBA48, in terms of booted disk geometry for the disklabels and filesystems, will the only difference be the number of available cylinders between LBA48 and "regular" (28-bit) LBA? Elucidating: -Suppose I install 4.9 or 5.0 off the bootable install CD with the default LBA48/PIO support, and make sure that all slices fall below the 128 GiB boundary. I think disklabel says that slices need to be on cylinder boundaries, so I would just make sure to stop allocating slices when I reached the last cylinder fully contained at or below 128 GiB. -After that, I then boot the system off disk, patch src/sys/dev/ata/wd.c to turn off LBA48, build a new kernel, and boot using the new kernel. -Then will all the slices and filesystems I created earlier be accessible just the same, without any errors? Would there be any translation differences other than the number of cylinders that would cause issues? Would there be any kind of free space tracking in the partition table that would need to be addressed? (Q3): Also, is there an easy way to make sure the controller is being set to use DMA at all? I'm not an expert in the IDE / ATA drivers, but it looks like once the controller and device are known to be capable of DMA, the determination is made on a specific transfer-by-transfer basis as to whether DMA or PIO get used? I base this on _wdc_ata_bio_start in src/sys/dev/ata/ata_wdc.c . So for the Blade 150, when acer_dma_init is eventually called from within _wdc_ata_bio_start , the LBA48-based decision to return EINVAL results in a "silent" downgrade to PIO mode, on a per-transfer basis. Is my understanding correct? If so it doesn't appear like there's a straightforward way to make sure that generally speaking, transfers are or are not using DMA, but again I'd like to ask you experts. Thank you very much.
