Hello Alan, Friday, June 26, 2009, 3:46:39 PM, you wrote: > The bmdma_start shouldn't be needed. Libata knows about using the cache > coherency dma interfaces and uses them. Correct, libata does call corresponding interface and the functions are defined for the cpu. But this architecture is buggy. It is necessary to clean (write back) complete cache before DMA write operation even if the corresponding range is already cleaned, otherwise few bytes in the written block are corrupted at random offset. I've spent many days playing with dma interface and even calculating md5sum of every written block before I had to accept this fact. > The bmdma end is no standard and polls the status up to 100 times until > it gives a sensible looking answer. That may be needed but its hard to > guess from just horrible code if that was someone's random debug hacks or > a real chip erratum. Chip is really weird. A group of enthusiasts implemented slave device support for it. As I could understand from their explanation the controller switches to a specific DVD-LOADER mode as soon as kernel sends any command to the slave device, so they had to patch sources and add a strange looking command OUT_BYTE((head|drive->select.all) & ~(1<<4), IDE_SELECT_REG); everywhere the slave device is accessed to cheat the controller and let it believe it talks to the master. Slave device remains active because it was already selected but the controller assumes we are talking to the master and does not switch to DVD-LOADER mode. > I notice the 2.4.17 patches you are referencing don't enable MWDMA either > (#undef EBABLE_BMDMA) so does MWDMA actually work on the hardware ? Here is a part of the boot log with 2.4.17 kernel. Speed is set to 0x22 (XFER_MW_DMA_2), that's why I assume it should work. I can limit allowed modes to PIO-only in 2.6 kernel, the driver is working but it is too slow. Uniform Multi-Platform E-IDE driver Revision: 6.31 ide: Assuming 50MHz system bus speed for PIO modes; override with idebus=xx JASPER ide controller activated ide0: BM-DMA at 0x500e00-0x500e0f, BIOS settings: hda:pio, hdb:pio hda: IDE_SELECT Reg = 000000a0 hda: IDE_SIDETIM Reg = 00000000 hda: IDE_SELECT Reg = 000000a0 hda: IDE_SIDETIM Reg = 00000000 hda: 9929D05E59V1.500P3311077, ATAPI CD/DVD-ROM drive IDE: waiting for drives to settle... hdb: IDE_SELECT Reg = 000000b0 hdb: IDE_SIDETIM Reg = 00000000 hdb: SAMSUNG HD300LD, ATA DISK drive ide0 at 0x500bf0-0x500bf7,0x500be6 on irq 11 hdb: ignore DMA off message. model = SAMSUNG HD300LD firmware version = WK100-12 jasper_config_drive_for_dma: capability = 0x002f field_valid = 0x0007 dma_ultra = 0x003f dma_1word (s) = 0x0000 dma_mword (m) = 0x0407 autodma = 0x0001 jasper_tune_chipset: speed = 22 ***** init_idedisk_capacity: set_max_ext=15647024, capacity_2=586070255 hdb: 586070255 sectors (300068 MB) w/8192KiB Cache, CHS=36481/255/63, (U)DMA hda: ignore DMA off message. model = 9929D05E59V1.500P3311077 firmware version = jasper_config_drive_for_dma: capability = 0x000b field_valid = 0x0002 dma_ultra = 0x0000 dma_1word (s) = 0x0000 dma_mword (m) = 0x0407 autodma = 0x0001 jasper_tune_chipset: speed = 22 hda: ATAPI 32X DVD-ROM drive, 256kB Cache, DMA Uniform CD-ROM driver Revision: 3.12 Partition check: /dev/ide/host0/bus0/target1/lun0: p1 < p5 p6 > -- Best regards, Andrei mailto:andrei.martynov@xxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
