From 4c647338267e14c93892f6f125f17ea2419eea51 Mon Sep 17 00:00:00 2001 From: Santosh Shilimkar Date: Mon, 20 Sep 2010 10:32:07 +0300 Subject: [PATCH] usb: musb: host: Issue a memory barrier before starting DMA This patch fixes the issue which was observed while transfering a large file ( > 20MB) over USB (OMAP MUSB controller acts as USB host) to an attached USB thumb drive. It was found that CDB field of CBW packet was set to 0x0. This was due to missing a barrier before DMA engine starts transfer. This buffer is allocated using dma_alloc_coherent which gives non-cacheble but bufferable memory and hence needed a write memory barrier to flush the write buffer. More info on this thread is here: http://www.spinics.net/lists/linux-omap/msg33987.html Signed-off-by: Santosh Shilimkar Signed-off-by: Maulik Mankad Cc: Russell King Signed-off-by: Felipe Balbi Signed-off-by: Greg Kroah-Hartman --- drivers/usb/musb/musb_host.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c index 877d20b1dff9..9e65c47cc98b 100644 --- a/drivers/usb/musb/musb_host.c +++ b/drivers/usb/musb/musb_host.c @@ -660,6 +660,12 @@ static bool musb_tx_dma_program(struct dma_controller *dma, qh->segsize = length; + /* + * Ensure the data reaches to main memory before starting + * DMA transfer + */ + wmb(); + if (!dma->channel_program(channel, pkt_size, mode, urb->transfer_dma + offset, length)) { dma->channel_release(channel); -- 2.20.1