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authorDavid Brownell <dbrownell@users.sourceforge.net>2009-04-22 14:33:40 -0400
committerBartlomiej Zolnierkiewicz <bzolnier@gmail.com>2009-04-22 14:33:40 -0400
commitdb2f38c22ea3f545be3b5772e5f9dc5861b74536 (patch)
tree57b07f93fb6e474761a31446c96a9821e1aa98d8 /drivers/message
parent15da90b516e9da92cc1d90001e640fd6707d0e27 (diff)
palm_bk3710: UDMA performance fix
Fix UDMA throughput bug: tCYC averages t2CYCTYP/2, but the code previously assumed it was the same as t2CYCTYP. (That is, it was using just one clock edge, not both.) Move the table's type declaration so it's adjacent to the table, making it more clear what those numbers mean. On one system this change increased throughput by almost 4x: UDMA/66 sometimes topped 23 MB/sec (on a drive known to do much better). On another system it was around a 10% win (UDMA/66 up to 7+ MB/sec). The difference might be caused by the ratio between memory and IDE clocks. In the system with large speedup, this was exactly 2 (as a workaround for a rev 1.1 silicon bug). The other system used a more standard ratio of 1.63 (and rev 2.1 silicon) ... clock domain synch might have some issues, they're not unheard-of. Signed-off-by: David Brownell <dbrownell@users.sourceforge.net> Acked-by: Sergei Shtylyov <sshtylyov@ru.mvista.com> Signed-off-by: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
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