[PATCH 2/4] usb: musb: Fix receiving of bigger buffers

[Pali Rohár]

If musb_peri_rx_ep() was called to processed received HW buffer but U-Boot
cannot read it yet (e.g. because U-Boot SW buffer is full) then interrupt
was marked as processed but HW buffer stayed unprocessed.

U-Boot tried to process this buffer again when it receive interrupt again,
but it can receive it only when sender (host) send a new data. As sender
(host) is not going to send a new data until U-Boot process current data
this issue caused a deadlock in case sender (host) is emitting data faster
than U-Boot can process it.

Reading musb intrrx register automatically clears this register and mark
interrupt as processed. So to prevent marking interrupt in U-Boot as
processed and a new variable pending_intrrx which would contain unprocessed
bits of intrrx register.

And as a second step, every time when musb_peri_rx_ep() is called and there
are waiting data to be processed (signaled by MUSB_RXCSR_RXPKTRDY) either
acknowledge sender (via musb_peri_rx_ack()) that whole HW buffer was
processed or set corresponding bit in pending_intrrx that HW buffer was not
fully processed yet and next iteration is required after U-Boot allocate
space for reading HW buffer.

This patch fixes receiving large usb buffers, e.g. file transfer via Kermit
protocol implemented by 'loadb' U-Boot command over usbtty serial console.

Signed-off-by: Pali Rohár <pali at kernel.org>
---
 drivers/usb/musb/musb_udc.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/musb/musb_udc.c b/drivers/usb/musb/musb_udc.c
index 28719cc3f6..7c74422623 100644
--- a/drivers/usb/musb/musb_udc.c
+++ b/drivers/usb/musb/musb_udc.c
@@ -104,6 +104,8 @@ struct usb_endpoint_instance *ep0_endpoint;
 static struct usb_device_instance *udc_device;
 static int enabled;
 
+u16 pending_intrrx;
+
 #ifdef MUSB_DEBUG
 static void musb_db_regs(void)
 {
@@ -664,7 +666,10 @@ static void musb_peri_rx_ep(unsigned int ep)
 				/* The common musb fifo reader */
 				read_fifo(ep, length, data);
 
-				musb_peri_rx_ack(ep);
+				if (length == peri_rxcount)
+					musb_peri_rx_ack(ep);
+				else
+					pending_intrrx |= (1 << ep);
 
 				/*
 				 * urb's actual_length is updated in
@@ -677,18 +682,24 @@ static void musb_peri_rx_ep(unsigned int ep)
 					serial_printf("ERROR : %s %d no space "
 						      "in rcv buffer\n",
 						      __PRETTY_FUNCTION__, ep);
+
+				pending_intrrx |= (1 << ep);
 			}
 		} else {
 			if (debug_level > 0)
 				serial_printf("ERROR : %s %d problem with "
 					      "endpoint\n",
 					      __PRETTY_FUNCTION__, ep);
+
+			pending_intrrx |= (1 << ep);
 		}
 
 	} else {
 		if (debug_level > 0)
 			serial_printf("ERROR : %s %d with nothing to do\n",
 				      __PRETTY_FUNCTION__, ep);
+
+		musb_peri_rx_ack(ep);
 	}
 }
 
@@ -770,6 +781,9 @@ void udc_irq(void)
 			intrrx = readw(&musbr->intrrx);
 			intrtx = readw(&musbr->intrtx);
 
+			intrrx |= pending_intrrx;
+			pending_intrrx = 0;
+
 			if (intrrx)
 				musb_peri_rx(intrrx);
 
-- 
2.20.1