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    Subject[PATCH 4.1 109/159] stmmac: troubleshoot unexpected bits in des0 & des1
    Date
    4.1-stable review patch.  If anyone has any objections, please let me know.

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

    From: Alexey Brodkin <Alexey.Brodkin@synopsys.com>

    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: stable@vger.kernel.org
    Cc: David Miller <davem@davemloft.net>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

    ---
    drivers/net/ethernet/stmicro/stmmac/descs.h | 2 +
    drivers/net/ethernet/stmicro/stmmac/enh_desc.c | 3 +
    drivers/net/ethernet/stmicro/stmmac/norm_desc.c | 3 +
    drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 44 +++++++++++-----------
    4 files changed, 28 insertions(+), 24 deletions(-)

    --- a/drivers/net/ethernet/stmicro/stmmac/descs.h
    +++ b/drivers/net/ethernet/stmicro/stmmac/descs.h
    @@ -158,6 +158,8 @@ 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
    @@ -240,6 +240,7 @@ static int enh_desc_get_rx_status(void *
    static void enh_desc_init_rx_desc(struct dma_desc *p, int disable_rx_ic,
    int mode, int end)
    {
    + p->des01.all_flags = 0;
    p->des01.erx.own = 1;
    p->des01.erx.buffer1_size = BUF_SIZE_8KiB - 1;

    @@ -254,7 +255,7 @@ static void enh_desc_init_rx_desc(struct

    static void enh_desc_init_tx_desc(struct dma_desc *p, int mode, int end)
    {
    - p->des01.etx.own = 0;
    + p->des01.all_flags = 0;
    if (mode == STMMAC_CHAIN_MODE)
    ehn_desc_tx_set_on_chain(p, end);
    else
    --- a/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
    +++ b/drivers/net/ethernet/stmicro/stmmac/norm_desc.c
    @@ -123,6 +123,7 @@ static int ndesc_get_rx_status(void *dat
    static void ndesc_init_rx_desc(struct dma_desc *p, int disable_rx_ic, int mode,
    int end)
    {
    + p->des01.all_flags = 0;
    p->des01.rx.own = 1;
    p->des01.rx.buffer1_size = BUF_SIZE_2KiB - 1;

    @@ -137,7 +138,7 @@ static void ndesc_init_rx_desc(struct dm

    static void ndesc_init_tx_desc(struct dma_desc *p, int mode, int end)
    {
    - p->des01.tx.own = 0;
    + p->des01.all_flags = 0;
    if (mode == STMMAC_CHAIN_MODE)
    ndesc_tx_set_on_chain(p, end);
    else
    --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
    +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
    @@ -1192,41 +1192,41 @@ static int alloc_dma_desc_resources(stru
    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;
    }
    }



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