Messages in this thread | | | Date | Tue, 24 Nov 2015 12:21:18 +1100 (AEDT) | From | Finn Thain <> | Subject | Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers |
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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.
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