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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? > It's to deal with readl_relaxed in mv_chan_is_busy. I'll change to > regular readl in v2. I just want to know which variable need read barrier() ? Frank > > > > 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 > > >