stmmac: troubleshoot unexpected bits in des0 & des1

commit f1590670ce069eefeb93916391a67643e6ad1630 upstream.

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: David Miller <davem@davemloft.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
[bwh: Backported to 3.2:
 - Adjust context, indentation
 - Normal and extended descriptors are allocated in the same place here]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: Alexey Brodkin <Alexey.Brodkin@synopsys.com>

diff --git a/drivers/net/ethernet/stmicro/stmmac/descs.h b/drivers/net/ethernet/stmicro/stmmac/descs.h
index 9820ec8..e93a0bf 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/descs.h
+++ b/drivers/net/ethernet/stmicro/stmmac/descs.h
@@ -153,6 +153,8 @@ struct dma_desc {
                        u32 buffer2_size:13;
                        u32 reserved4:3;
                } etx;          /* -- enhanced -- */
+
+               u64 all_flags;
        } des01;
        unsigned int des2;
        unsigned int des3;

diff --git a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
index d879763..73e647b 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/enh_desc.c
@@ -232,6 +232,7 @@ static void enh_desc_init_rx_desc(struct dma_desc *p, unsigned int ring_size,
 {
        int i;
        for (i = 0; i < ring_size; i++) {
+               p->des01.all_flags = 0;
                p->des01.erx.own = 1;
                p->des01.erx.buffer1_size = BUF_SIZE_8KiB - 1;
 
@@ -248,7 +249,7 @@ static void enh_desc_init_tx_desc(struct dma_desc *p, unsigned int ring_size)
        int i;
 
        for (i = 0; i < ring_size; i++) {
-               p->des01.etx.own = 0;
+               p->des01.all_flags = 0;
                ehn_desc_tx_set_on_ring_chain(p, (i == ring_size - 1));
                p++;
        }

diff --git a/drivers/net/ethernet/stmicro/stmmac/norm_desc.c b/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
index fda5d2b..5bf9c37 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
+++ b/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
@@ -126,6 +126,7 @@ static void ndesc_init_rx_desc(struct dma_desc *p, unsigned int ring_size,
 {
        int i;
        for (i = 0; i < ring_size; i++) {
+               p->des01.all_flags = 0;
                p->des01.rx.own = 1;
                p->des01.rx.buffer1_size = BUF_SIZE_2KiB - 1;
 
@@ -141,7 +142,7 @@ static void ndesc_init_tx_desc(struct dma_desc *p, unsigned int ring_size)
 {
        int i;
        for (i = 0; i < ring_size; i++) {
-               p->des01.tx.own = 0;
+               p->des01.all_flags = 0;
                ndesc_tx_set_on_ring_chain(p, (i == (ring_size - 1)));
                p++;
        }

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index d4d2bc1..05852e3 100644 (file)
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -441,19 +441,17 @@ static void init_dma_desc_rings(struct net_device *dev)
        priv->rx_skbuff =
            kmalloc(sizeof(struct sk_buff *) * rxsize, GFP_KERNEL);
        priv->dma_rx =
-           (struct dma_desc *)dma_alloc_coherent(priv->device,
-                                                 rxsize *
-                                                 sizeof(struct dma_desc),
-                                                 &priv->dma_rx_phy,
-                                                 GFP_KERNEL);
+           (struct dma_desc *)dma_zalloc_coherent(priv->device, rxsize *
+                                                  sizeof(struct dma_desc),
+                                                  &priv->dma_rx_phy,
+                                                  GFP_KERNEL);
        priv->tx_skbuff = kmalloc(sizeof(struct sk_buff *) * txsize,
                                       GFP_KERNEL);
        priv->dma_tx =
-           (struct dma_desc *)dma_alloc_coherent(priv->device,
-                                                 txsize *
-                                                 sizeof(struct dma_desc),
-                                                 &priv->dma_tx_phy,
-                                                 GFP_KERNEL);
+           (struct dma_desc *)dma_zalloc_coherent(priv->device, txsize *
+                                                  sizeof(struct dma_desc),
+                                                  &priv->dma_tx_phy,
+                                                  GFP_KERNEL);
 
        if ((priv->dma_rx == NULL) || (priv->dma_tx == NULL)) {
                pr_err("%s:ERROR allocating the DMA Tx/Rx desc\n", __func__);