[PATCH 2/7] net: ethernet: ti: cpdma: fix desc re-queuing

The currently processing cpdma descriptor with EOQ flag set may
contain two values in Next Descriptor Pointer field:
- valid pointer: means CPDMA missed addition of new desc in queue;
- null: no more descriptors in queue.
In the later case, it's not required to write to HDP register, but now
CPDMA does it.

Hence, add additional check for Next Descriptor Pointer != null in
cpdma_chan_process() function before writing in HDP register.

Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
---
 drivers/net/ethernet/ti/davinci_cpdma.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/ti/davinci_cpdma.c b/drivers/net/ethernet/ti/davinci_cpdma.c
index 0924014..379314f 100644
--- a/drivers/net/ethernet/ti/davinci_cpdma.c
+++ b/drivers/net/ethernet/ti/davinci_cpdma.c

@@ -1152,7 +1152,7 @@ static int __cpdma_chan_process(struct cpdma_chan *chan)
 	chan->count--;
 	chan->stats.good_dequeue++;
 
-	if (status & CPDMA_DESC_EOQ) {
+	if ((status & CPDMA_DESC_EOQ) && chan->head) {
 		chan->stats.requeue++;
 		chan_write(chan, hdp, desc_phys(pool, chan->head));
 	}

-- 
2.10.1