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Subject[PATCH 4.14 026/193] net: mvneta: fix handling of the Tx descriptor counter
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Simon Guinot <simon.guinot@sequanux.org>

commit 0d63785c6b94b5d2f095f90755825f90eea791f5 upstream.

The mvneta controller provides a 8-bit register to update the pending
Tx descriptor counter. Then, a maximum of 255 Tx descriptors can be
added at once. In the current code the mvneta_txq_pend_desc_add function
assumes the caller takes care of this limit. But it is not the case. In
some situations (xmit_more flag), more than 255 descriptors are added.
When this happens, the Tx descriptor counter register is updated with a
wrong value, which breaks the whole Tx queue management.

This patch fixes the issue by allowing the mvneta_txq_pend_desc_add
function to process more than 255 Tx descriptors.

Fixes: 2a90f7e1d5d0 ("net: mvneta: add xmit_more support")
Signed-off-by: Simon Guinot <simon.guinot@sequanux.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/net/ethernet/marvell/mvneta.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/net/ethernet/marvell/mvneta.c
+++ b/drivers/net/ethernet/marvell/mvneta.c
@@ -816,11 +816,14 @@ static void mvneta_txq_pend_desc_add(str
{
u32 val;

- /* Only 255 descriptors can be added at once ; Assume caller
- * process TX desriptors in quanta less than 256
- */
- val = pend_desc + txq->pending;
- mvreg_write(pp, MVNETA_TXQ_UPDATE_REG(txq->id), val);
+ pend_desc += txq->pending;
+
+ /* Only 255 Tx descriptors can be added at once */
+ do {
+ val = min(pend_desc, 255);
+ mvreg_write(pp, MVNETA_TXQ_UPDATE_REG(txq->id), val);
+ pend_desc -= val;
+ } while (pend_desc > 0);
txq->pending = 0;
}


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