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SubjectRe: [PATCH v1 4/5] dmaengine: Add driver for NVIDIA Tegra AHB DMA controller
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On 28.09.2017 12:29, Vinod Koul wrote:
>> + 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

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