stmmac: troubleshoot unexpected bits in des0 & des1

Current implementation of descriptor init procedure only takes
care about setting/clearing ownership flag in "des0"/"des1"
fields while it is perfectly possible to get unexpected bits
set because of the following factors:

 [1] On driver probe underlying memory allocated with
     dma_alloc_coherent() might not be zeroed and so
     it will be filled with garbage.

 [2] During driver operation some bits could be set by SD/MMC
     controller (for example error flags etc).

And unexpected and/or randomly set flags in "des0"/"des1"
fields may lead to unpredictable behavior of GMAC DMA block.

This change addresses both items above with:

 [1] Use of dma_zalloc_coherent() instead of simple
     dma_alloc_coherent() to make sure allocated memory is
     zeroed. That shouldn't affect performance because
     this allocation only happens once on driver probe.

 [2] Do explicit zeroing of both "des0" and "des1" fields
     of all buffer descriptors during initialization of
     DMA transfer.

And while at it fixed identation of dma_free_coherent()
counterpart as well.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Giuseppe Cavallaro <peppe.cavallaro@st.com>
Cc: arc-linux-dev@synopsys.com
Cc: linux-kernel@vger.kernel.org
Cc: stable@vger.kernel.org
Cc: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 22 insertions, 22 deletions

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 2c5ce2baca87..2e299e0949d7 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -1189,41 +1189,41 @@ static int alloc_dma_desc_resources(struct stmmac_priv *priv)
 		goto err_tx_skbuff;
 
 	if (priv->extend_desc) {
-		priv->dma_erx = dma_alloc_coherent(priv->device, rxsize *
-						   sizeof(struct
-							  dma_extended_desc),
-						   &priv->dma_rx_phy,
-						   GFP_KERNEL);
+		priv->dma_erx = dma_zalloc_coherent(priv->device, rxsize *
+						    sizeof(struct
+							   dma_extended_desc),
+						    &priv->dma_rx_phy,
+						    GFP_KERNEL);
 		if (!priv->dma_erx)
 			goto err_dma;
 
-		priv->dma_etx = dma_alloc_coherent(priv->device, txsize *
-						   sizeof(struct
-							  dma_extended_desc),
-						   &priv->dma_tx_phy,
-						   GFP_KERNEL);
+		priv->dma_etx = dma_zalloc_coherent(priv->device, txsize *
+						    sizeof(struct
+							   dma_extended_desc),
+						    &priv->dma_tx_phy,
+						    GFP_KERNEL);
 		if (!priv->dma_etx) {
 			dma_free_coherent(priv->device, priv->dma_rx_size *
-					sizeof(struct dma_extended_desc),
-					priv->dma_erx, priv->dma_rx_phy);
+					  sizeof(struct dma_extended_desc),
+					  priv->dma_erx, priv->dma_rx_phy);
 			goto err_dma;
 		}
 	} else {
-		priv->dma_rx = dma_alloc_coherent(priv->device, rxsize *
-						  sizeof(struct dma_desc),
-						  &priv->dma_rx_phy,
-						  GFP_KERNEL);
+		priv->dma_rx = dma_zalloc_coherent(priv->device, rxsize *
+						   sizeof(struct dma_desc),
+						   &priv->dma_rx_phy,
+						   GFP_KERNEL);
 		if (!priv->dma_rx)
 			goto err_dma;
 
-		priv->dma_tx = dma_alloc_coherent(priv->device, txsize *
-						  sizeof(struct dma_desc),
-						  &priv->dma_tx_phy,
-						  GFP_KERNEL);
+		priv->dma_tx = dma_zalloc_coherent(priv->device, txsize *
+						   sizeof(struct dma_desc),
+						   &priv->dma_tx_phy,
+						   GFP_KERNEL);
 		if (!priv->dma_tx) {
 			dma_free_coherent(priv->device, priv->dma_rx_size *
-					sizeof(struct dma_desc),
-					priv->dma_rx, priv->dma_rx_phy);
+					  sizeof(struct dma_desc),
+					  priv->dma_rx, priv->dma_rx_phy);
 			goto err_dma;
 		}
 	}