usb: musb: fix cppi channel teardown for isoch transfer

After a few iterations of start/stop UVC camera streaming, the streaming
stops.

This patch adds 250us delay in the cppi channel abort path to let cppi
drain properly.

Using 50us delay seems to be too aggressive, some webcams are still
broken. 250us is the original value used in TI 3.2 kernel.

Signed-off-by: Bin Liu <b-liu@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

diff --git a/drivers/usb/musb/musb_cppi41.c b/drivers/usb/musb/musb_cppi41.c
index d07cafb7d5f5a1d6c992d184dff22cd53b48b3de..e499b862a946f16ff8a8c7fc4694c4da93fd4c74 100644 (file)
--- a/drivers/usb/musb/musb_cppi41.c
+++ b/drivers/usb/musb/musb_cppi41.c
@@ -551,6 +551,9 @@ static int cppi41_dma_channel_abort(struct dma_channel *channel)
        } else {
                cppi41_set_autoreq_mode(cppi41_channel, EP_MODE_AUTOREQ_NONE);
 
+               /* delay to drain to cppi dma pipeline for isoch */
+               udelay(250);
+
                csr = musb_readw(epio, MUSB_RXCSR);
                csr &= ~(MUSB_RXCSR_H_REQPKT | MUSB_RXCSR_DMAENAB);
                musb_writew(epio, MUSB_RXCSR, csr);