[PATCH 3.2 047/110] stmmac: troubleshoot unexpected bits in des0 & des1
From: Ben Hutchings <hidden>
Date: 2015-08-10 10:16:18
Also in:
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3.2.71-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Alexey Brodkin <redacted>
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 <redacted>
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 <redacted>
------ 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; --- 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 { 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 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++; } --- 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 dm { 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 dm { 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++; } --- 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 n 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__);