Commit 65111084c6 ("USB: more omap_udc updates (dma and omap1710)")
added setting for DMA burst 4 mode. But I think this should be undone for
two reasons:
- It breaks DMA on 15xx boards - transfers just silently stall.
- On newer OMAP1 boards, like Nokia 770 (omap1710), there is no measurable
performance impact when testing TCP throughput with g_ether with large
15000 byte MTU size.
It's also worth noting that when the original change was made, the
OMAP_DMA_DATA_BURST_4 handling in arch/arm/plat-omap/dma.c was broken, and
actually resulted in the same as the OMAP_DMA_DATA_BURST_DIS i.e. burst
disabled. This was fixed not until a couple kernel releases later in an
unrelated commit 1a8bfa1eb9 ("[ARM] 3142/1: OMAP 2/5: Update files
common to omap1 and omap2").
So based on this it seems there was never really a very good reason to
enable this burst mode in omap_udc, so remove it now to allow 15xx DMA
to work again (it provides 2x throughput compared to PIO mode).
Fixes: 65111084c6 ("[PATCH] USB: more omap_udc updates (dma and omap1710)")
Cc: stable <stable@kernel.org>
Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Link: https://patch.msgid.link/ad06qHLclWHeSGnV@darkstar.musicnaut.iki.fi
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
3f91484f6c