On Tuesday 24 November 2015 13:03:17 Ondrej Zary wrote: > On Tuesday 24 November 2015, Finn Thain wrote: > > > > On Tue, 24 Nov 2015, Ondrej Zary wrote: > > > > > 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?). > > > > When you said, the "PDMA operation hangs waiting forever", I figured that > > you had hit an infinite loop in NCR5380_pread()... but now I'm lost. > > The first 128-byte PDMA ended successfully (ignoring what happened to the > remaining 126 bytes), then a next request for 254 bytes came. This resulted > in a new 128-byte PDMA and that hanged (in one of its possibly infinite loops > without a timeout). > > > My main concern here is to confirm that I didn't break anything e.g. with > > patch 24 or 41. It would be nice to know that this hang is not the result > > of a new bug. > > PDMA was already broken before so it's hard to tell. I can try to modify > the unpatched driver to see if PDMA is broken the same way. Just tested the driver without your patches and it's broken exactly the same way. -- Ondrej Zary -- 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
