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    Subject[PATCH 7/8] dmaengine/dw_dmac: Unmap all memory buffers after completion of slave transfers
    Date
    Currently, after completion of transfer, source address or destination address
    of only the first LLI descriptor is unmapped. And length passed for unmap is
    total length of all descriptors in the list. Which means unmapping code assumed
    that the memory buffers pointed to by the descriptors will be physically
    contiguous, which might not be the case. It is possible for other drivers to
    pass sglist to slave_sg(), in which all buffers are scattered throughout the
    memory.

    This patch intends to fix this wrong expectation of dw_dmac. Now, first desc
    will not contain total length of transfer. But individual descriptors will
    contain their individual lengths. Finally, we will call unmap for all
    descriptors.

    Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
    ---
    drivers/dma/dw_dmac.c | 49 +++++++++++++++++++++++++++++++------------------
    1 files changed, 31 insertions(+), 18 deletions(-)

    diff --git a/drivers/dma/dw_dmac.c b/drivers/dma/dw_dmac.c
    index 8698d3b..c33c06b 100644
    --- a/drivers/dma/dw_dmac.c
    +++ b/drivers/dma/dw_dmac.c
    @@ -231,6 +231,14 @@ static void dwc_dostart(struct dw_dma_chan *dwc, struct dw_desc *first)

    /*----------------------------------------------------------------------*/

    +#define dw_dmac_unmap(utype, _desc, _child, _buf, _dir) \
    +do { \
    + list_for_each_entry(_child, &_desc->tx_list, desc_node) \
    + dma_unmap_##utype(parent, _child->lli._buf, \
    + _child->len, _dir); \
    + dma_unmap_##utype(parent, _desc->lli._buf, _desc->len, _dir); \
    +} while (0)
    +
    static void
    dwc_descriptor_complete(struct dw_dma_chan *dwc, struct dw_desc *desc,
    bool callback_required)
    @@ -264,19 +272,19 @@ dwc_descriptor_complete(struct dw_dma_chan *dwc, struct dw_desc *desc,
    struct device *parent = chan2parent(&dwc->chan);
    if (!(txd->flags & DMA_COMPL_SKIP_DEST_UNMAP)) {
    if (txd->flags & DMA_COMPL_DEST_UNMAP_SINGLE)
    - dma_unmap_single(parent, desc->lli.dar,
    - desc->len, DMA_FROM_DEVICE);
    + dw_dmac_unmap(single, desc, child, dar,
    + DMA_FROM_DEVICE);
    else
    - dma_unmap_page(parent, desc->lli.dar,
    - desc->len, DMA_FROM_DEVICE);
    + dw_dmac_unmap(page, desc, child, dar,
    + DMA_FROM_DEVICE);
    }
    if (!(txd->flags & DMA_COMPL_SKIP_SRC_UNMAP)) {
    if (txd->flags & DMA_COMPL_SRC_UNMAP_SINGLE)
    - dma_unmap_single(parent, desc->lli.sar,
    - desc->len, DMA_TO_DEVICE);
    + dw_dmac_unmap(single, desc, child, sar,
    + DMA_TO_DEVICE);
    else
    - dma_unmap_page(parent, desc->lli.sar,
    - desc->len, DMA_TO_DEVICE);
    + dw_dmac_unmap(page, desc, child, sar,
    + DMA_TO_DEVICE);
    }
    }

    @@ -676,6 +684,7 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
    desc->lli.dar = dest + offset;
    desc->lli.ctllo = ctllo;
    desc->lli.ctlhi = xfer_count;
    + desc->len = xfer_count << src_width;

    if (!first) {
    first = desc;
    @@ -701,7 +710,6 @@ dwc_prep_dma_memcpy(struct dma_chan *chan, dma_addr_t dest, dma_addr_t src,
    DMA_TO_DEVICE);

    first->txd.flags = flags;
    - first->len = len;

    return &first->txd;

    @@ -725,7 +733,6 @@ dwc_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
    unsigned int mem_width;
    unsigned int i;
    struct scatterlist *sg;
    - size_t total_len = 0;

    dev_vdbg(chan2dev(chan), "prep_dma_slave\n");

    @@ -774,6 +781,7 @@ slave_sg_todev_fill_desc:
    }

    desc->lli.ctlhi = dlen >> mem_width;
    + desc->len = dlen;

    if (!first) {
    first = desc;
    @@ -787,7 +795,6 @@ slave_sg_todev_fill_desc:
    &first->tx_list);
    }
    prev = desc;
    - total_len += dlen;

    if (len)
    goto slave_sg_todev_fill_desc;
    @@ -831,6 +838,7 @@ slave_sg_fromdev_fill_desc:
    len = 0;
    }
    desc->lli.ctlhi = dlen >> reg_width;
    + desc->len = dlen;

    if (!first) {
    first = desc;
    @@ -844,7 +852,6 @@ slave_sg_fromdev_fill_desc:
    &first->tx_list);
    }
    prev = desc;
    - total_len += dlen;

    if (len)
    goto slave_sg_fromdev_fill_desc;
    @@ -863,8 +870,6 @@ slave_sg_fromdev_fill_desc:
    prev->txd.phys, sizeof(prev->lli),
    DMA_TO_DEVICE);

    - first->len = total_len;
    -
    return &first->txd;

    err_desc_get:
    @@ -950,11 +955,19 @@ dwc_tx_status(struct dma_chan *chan,
    ret = dma_async_is_complete(cookie, last_complete, last_used);
    }

    - if (ret != DMA_SUCCESS)
    - dma_set_tx_state(txstate, last_complete, last_used,
    - dwc_first_active(dwc)->len);
    - else
    + if (ret != DMA_SUCCESS) {
    + struct dw_desc *desc, *child;
    + unsigned int len;
    +
    + desc = dwc_first_active(dwc);
    + len = desc->len;
    + list_for_each_entry(child, &desc->tx_list, desc_node)
    + len += child->len;
    +
    + dma_set_tx_state(txstate, last_complete, last_used, len);
    + } else {
    dma_set_tx_state(txstate, last_complete, last_used, 0);
    + }

    if (dwc->paused)
    return DMA_PAUSED;
    --
    1.7.8.110.g4cb5d


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