Avoid hw_desc array overrun in dw-axi-dmac
I have a use case where nr_buffers = 3 and in which each descriptor is composed by 3 segments, resulting in the DMA channel descs_allocated to be 9. Since axi_desc_put() handles the hw_desc considering the descs_allocated, this scenario would result in a kernel panic (hw_desc array will be overrun). To fix this, the proposal is to add a new member to the axi_dma_desc structure, where we keep the number of allocated hw_descs (axi_desc_alloc()) and use it in axi_desc_put() to handle the hw_desc array correctly. Additionally I propose to remove the axi_chan_start_first_queued() call after completing the transfer, since it was identified that unbalance can occur (started descriptors can be interrupted and transfer ignored due to DMA channel not being enabled). Signed-off-by: Joao Pinto <jpinto@synopsys.com> Link: https://lore.kernel.org/r/1711536564-12919-1-git-send-email-jpinto@synopsys.com Signed-off-by: Vinod Koul <vkoul@kernel.org>
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@ -302,6 +302,7 @@ static struct axi_dma_desc *axi_desc_alloc(u32 num)
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kfree(desc);
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return NULL;
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}
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desc->nr_hw_descs = num;
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return desc;
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}
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@ -328,7 +329,7 @@ static struct axi_dma_lli *axi_desc_get(struct axi_dma_chan *chan,
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static void axi_desc_put(struct axi_dma_desc *desc)
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{
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struct axi_dma_chan *chan = desc->chan;
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int count = atomic_read(&chan->descs_allocated);
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int count = desc->nr_hw_descs;
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struct axi_dma_hw_desc *hw_desc;
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int descs_put;
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@ -1139,9 +1140,6 @@ static void axi_chan_block_xfer_complete(struct axi_dma_chan *chan)
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/* Remove the completed descriptor from issued list before completing */
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list_del(&vd->node);
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vchan_cookie_complete(vd);
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/* Submit queued descriptors after processing the completed ones */
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axi_chan_start_first_queued(chan);
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}
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out:
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@ -104,6 +104,7 @@ struct axi_dma_desc {
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u32 completed_blocks;
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u32 length;
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u32 period_len;
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u32 nr_hw_descs;
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};
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struct axi_dma_chan_config {
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