Messages in this thread Patch in this message | | | From | Ong Boon Leong <> | Subject | [PATCH net 1/7] net: stmmac: fix error in updating rx tail pointer to last free entry | Date | Tue, 14 Jan 2020 10:01:10 +0800 |
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DMA_CH(#i)_RxDesc_Tail_Pointer points to an offset from the base and indicates the location of the last valid descriptor.
The change introduced by "net: stmmac: Update RX Tail Pointer to last free entry" incorrectly updates the RxDesc_Tail_Pointer and causess Rx operation to freeze in corner case. The issue is explained as follow:-
Say, cur_rx=1 and dirty_rx=0, then we have dirty=1 and entry=0 before the while (dirty-- > 0) loop of stmmac_rx_refill() is entered. When the while loop is 1st entered, Rx buffer[entry=0] is refilled and after entry++, then, entry=1. Now, the while loop condition check "dirty-- > 0" and the while loop bails out because dirty=0. Up to this point, the driver code works correctly.
However, the current implementation sets the Rx Tail Pointer to the location pointed by dirty_rx, just updated to the value of entry(=1). This is incorrect because the last Rx buffer that is refileld with empty buffer is with entry=0. In another words, the current logics always sets Rx Tail Pointer to the next Rx buffer to be refilled (too early).
So, we fix this by tracking the index of the most recently refilled Rx buffer by using "last_refill" and use "last_refill" to update the Rx Tail Pointer instead of using "entry" which points to the next dirty_rx to be refilled in future.
Fixes: 858a31ffc3d9 ("net: stmmac: Update RX Tail Pointer to last free entry")
Signed-off-by: Ong Boon Leong <boon.leong.ong@intel.com> --- drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index 80d59b7..a317f67 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -3417,6 +3417,7 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue) struct stmmac_rx_queue *rx_q = &priv->rx_queue[queue]; int len, dirty = stmmac_rx_dirty(priv, queue); unsigned int entry = rx_q->dirty_rx; + unsigned int last_refill = entry; len = DIV_ROUND_UP(priv->dma_buf_sz, PAGE_SIZE) * PAGE_SIZE; @@ -3471,12 +3472,13 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue) dma_wmb(); stmmac_set_rx_owner(priv, p, use_rx_wd); - + last_refill = entry; entry = STMMAC_GET_ENTRY(entry, DMA_RX_SIZE); } + rx_q->dirty_rx = entry; rx_q->rx_tail_addr = rx_q->dma_rx_phy + - (rx_q->dirty_rx * sizeof(struct dma_desc)); + (last_refill * sizeof(struct dma_desc)); stmmac_set_rx_tail_ptr(priv, priv->ioaddr, rx_q->rx_tail_addr, queue); } -- 2.7.4
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