Messages in this thread | | | From | Ondrej Zary <> | Subject | Re: [PATCH 00/71] More fixes, cleanup and modernization for NCR5380 drivers | Date | Tue, 24 Nov 2015 09:04:54 +0100 |
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On Tuesday 24 November 2015, Finn Thain wrote: > > 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?
No 126-byte PDMA. The 126 bytes were probably lost (or mixed with the next read?). The next read was also 254 bytes so another 128-byte PDMA transfer.
Then modified NCR5380_information_transfer() to transfer the remaining data (126 bytes in this case) using PIO. It did not help, the next PDMA transfer failed too.
> 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.
Yes, the flag was set.
-- Ondrej Zary
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