On 28.09.2017 12:29, Vinod Koul wrote:

quoted

+	default:
+		return -EINVAL;
+	}
+
+	ahb_seq  = burst << TEGRA_AHBDMA_CHANNEL_AHB_BURST_SHIFT;
+	ahb_seq |= TEGRA_AHBDMA_CHANNEL_ADDR_WRAP;
+	ahb_seq |= TEGRA_AHBDMA_CHANNEL_INTR_ENB;
+
+	writel_relaxed(ahb_seq,
+		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_SEQ);
+
+	writel_relaxed(ahb_addr,
+		       ahbdma_chan->regs + TEGRA_AHBDMA_CHANNEL_AHB_PTR);

oh no, you don't write to HW here. This can be called anytime when you have
txn running! You should save these and use them in prep_ calls.

BTW, some of the DMA drivers have exactly the same problem. I now see that it is
actually documented explicitly in provider.txt, but that's inconsistent across
the actual drivers.

-- 
Dmitry