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The descriptor pool is > allocated with dma_alloc_wc(), so writes sit in the CPU write buffers > and must be drained before the engine is allowed to read them. > > Program the next-descriptor pointer with writel() instead of > writel_relaxed(); the full accessor drains prior memory writes before > the MMIO write. > > In mv_xor_tx_submit() the appended chain link must be visible before the > busy-status register is read. Use a full mb() so the engine cannot fetch a > stale chain link and stall the channel after the CPU decides it is still > busy. > > Fixes: ff7b04796d98 ("dmaengine: DMA engine driver for Marvell XOR engine") > Assisted-by: LLM > Signed-off-by: Rosen Penev > --- > drivers/dma/mv_xor.c | 10 +++++++++- > 1 file changed, 9 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma/mv_xor.c b/drivers/dma/mv_xor.c > index c4e0dce3ca64..0de2b1ad5c30 100644 > --- a/drivers/dma/mv_xor.c > +++ b/drivers/dma/mv_xor.c > @@ -103,7 +103,10 @@ static u32 mv_chan_get_current_desc(struct mv_xor_chan *chan) > static void mv_chan_set_next_descriptor(struct mv_xor_chan *chan, > u32 next_desc_addr) > { > - writel_relaxed(next_desc_addr, XOR_NEXT_DESC(chan)); > + /* writel drains descriptor writes to DRAM before the engine > + * is pointed at them > + */ > + writel(next_desc_addr, XOR_NEXT_DESC(chan)); I remember this my comments before, should be v2 version? > } > > static void mv_chan_unmask_interrupts(struct mv_xor_chan *chan) > @@ -410,6 +413,11 @@ mv_xor_tx_submit(struct dma_async_tx_descriptor *tx) > /* fix up the hardware chain */ > mv_desc_set_next_desc(old_chain_tail, sw_desc->async_tx.phys); > > + /* make the new link visible to the engine before we read > + * the channel state, the device may fetch it at any point > + */ > + mb(); > + The first is readl_relaxed() in mv_chan_is_busy(), all io readl and writel is ordered. which part need mb() here? Frank > /* if the channel is not busy */ > if (!mv_chan_is_busy(mv_chan)) { > u32 current_desc = mv_chan_get_current_desc(mv_chan); > -- > 2.55.0 >