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
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