Re: [PATCH] MUSB: Fix aborted RX-DMA path

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Hello.

Anand Gadiyar wrote:

MUSB: Fix aborted RX-DMA path

In the MUSB rxstate function, if channel_program() returns an
error, then we use PIO mode to carry out that RX transfer.

For this to work correctly, we need to de-assert DMAENAB in
RXCSR.

Signed-off-by: Anand Gadiyar <gadiyar@xxxxxx>
Cc: Felipe Balbi <felipe.balbi@xxxxxxxxx>
Cc: David Brownell <dbrownell@xxxxxxxxxxxxxxxxxxxxx>
Cc: Ajay Kumar Gupta <ajay.gupta@xxxxxx>
---
(Resending with updated $SUBJECT. Sorry for the noise)

In current code, this bug is purely academic, since channel_program()
 always returns success. However, if it ever failed, then the
fix is needed. We spent some time to debug this when we deliberately
made channel_program fail (to test the PIO path), so I think this
fix is worth having.

It's probably not required for the stable trees.

diff --git a/drivers/usb/musb/musb_gadget.c b/drivers/usb/musb/musb_gadget.c
index 8b3c4e2..cfac24d 100644
--- a/drivers/usb/musb/musb_gadget.c
+++ b/drivers/usb/musb/musb_gadget.c
@@ -688,8 +688,15 @@ static void rxstate(struct musb *musb, struct musb_request *req)
 							transfer_size);
 				}
- if (use_dma)
+				if (use_dma) {

  Unneeded change -- you don't need braces around a single *return*.

 					return;
+				} else {
+					/* Need to clear DMAENAB for the
+					 * backup PIO mode transfer to work
+					 */
+					csr &= ~MUSB_RXCSR_DMAENAB;
+					musb_writew(epio, MUSB_RXCSR, csr);
+				}
 			}
 #endif	/* Mentor's DMA */

WBR, Sergei


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