On Mon, 23 Nov 2015, Ondrej Zary wrote: > > PDMA seems to be broken in multiple ways. NCR5380_pread cannot process > less than 128 bytes. In fact, 53C400 datasheet says that it's HW > limitation: non-modulo-128-byte transfers should use PIO. > > Adding > transfersize = round_down(transfersize, 128); > to generic_NCR5380_dma_xfer_len() improves the situation a bit. > > After modprobe, some small reads (8, 4, 24 and 64 bytes) are done using > PIO, then eight 512-byte reads using PDMA and then it fails on a > 254-byte read. First 128 bytes are read using PDMA and the next PDMA > operation hangs waiting forever for the host buffer to be ready. > A 128-byte PDMA receive followed by 126-byte PDMA receive? I don't see how that is possible given round_down(126, 128) == 0. Was this the actual 'len' argument to NCR5380_pread() in g_NCR5380.c? BTW, I presume that FLAG_NO_DMA_FIXUPS was set (which is the case if you pass ncr_53c400=1 option with modprobe). Otherwise you could see PDMA IO sizes like 127 etc. -- -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
