spi-topcliff-pch: Fix overrun issue
authorTomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Tue, 6 Sep 2011 08:16:38 +0000 (17:16 +0900)
committerGrant Likely <grant.likely@secretlab.ca>
Tue, 4 Oct 2011 16:10:50 +0000 (10:10 -0600)
commitf3e03e2eb0bcd9266720695b82a523e6bc526ff7
tree12184b7ed8bea50f0ca10ff44c7f37e5c1bb0e07
parent25e803f9c339a070cd7361e853aebde11b1f9217
spi-topcliff-pch: Fix overrun issue

We found that adding load, Rx data sometimes drops.(with DMA transfer mode)
The cause is that before starting Rx-DMA processing, Tx-DMA processing starts.
This causes FIFO overrun occurs.

This patch fixes the issue by modifying FIFO tx-threshold and DMA descriptor
size like below.

                      Current                   this patch
Rx-descriptor   4Byte+12Byte*341    -->    12Byte*340-4Byte-12Byte
Rx-threshold                   (Not modified)
Tx-descriptor   4Byte+12Byte*341    -->    16Byte-12Byte*340
Rx-threshold    12Byte              -->    2Byte

Signed-off-by: Tomoya MORINAGA <tomoya-linux@dsn.okisemi.com>
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
drivers/spi/spi-topcliff-pch.c