usb: musb: introduce dma_channel.rx_packet_done

The musb/cppi41 glue layer is capable of handling transactions that span
over more than one USB packet by reloading the DMA descriptors
partially. An urb is considered completed when either its transfer
buffer has been filled entirely (actual_length ==
transfer_buffer_length) or if a packet in the stream has less bytes than
the endpoint's wMaxPacketSize.

Once one of the above conditions is met, musb_dma_completion() is called
from cppi41_trans_done(). However, the final decision whether or not to
return the urb to its owner is made by the core and its determination of
the variable 'done' in musb_host_rx(). This code has currently no way of
knowing what the size of the last packet was, and whether or not to
give back the urb due to a short read.

Fix this by introducing a new boolean flag in 'struct dma_channel', and
set it from musb_cppi41.c. If set, it will make the core do what the
DMA layer decided and complete the urb.
Signed-off-by: Daniel Mack <zonque@gmail.com>
Acked-by: George Cherian <george.cherian@ti.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_cppi41.c

@@ -139,6 +139,7 @@ static void cppi41_trans_done(struct cppi41_dma_channel *cppi41_channel)
 		cppi41_channel->channel.actual_len =
 			cppi41_channel->transferred;
 		cppi41_channel->channel.status = MUSB_DMA_STATUS_FREE;
+		cppi41_channel->channel.rx_packet_done = true;
 		musb_dma_completion(musb, hw_ep->epnum, cppi41_channel->is_tx);
 	} else {
 		/* next iteration, reload */
@@ -450,6 +451,7 @@ static bool cppi41_configure_channel(struct dma_channel *channel,
 	dma_desc->callback = cppi41_dma_callback;
 	dma_desc->callback_param = channel;
 	cppi41_channel->cookie = dma_desc->tx_submit(dma_desc);
+	cppi41_channel->channel.rx_packet_done = false;
 
 	save_rx_toggle(cppi41_channel);
 	dma_async_issue_pending(dc);

drivers/usb/musb/musb_dma.h

@@ -129,6 +129,7 @@ struct dma_channel {
 	size_t			actual_len;
 	enum dma_channel_status	status;
 	bool			desired_mode;
+	bool			rx_packet_done;
 };
 
 /*

drivers/usb/musb/musb_host.c

@@ -1737,7 +1737,8 @@ void musb_host_rx(struct musb *musb, u8 epnum)
 		/* done if urb buffer is full or short packet is recd */
 		done = (urb->actual_length + xfer_len >=
 				urb->transfer_buffer_length
-			|| dma->actual_len < qh->maxpacket);
+			|| dma->actual_len < qh->maxpacket
+			|| dma->rx_packet_done);
 		}
 
 		/* send IN token for next packet, without AUTOREQ */