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    SubjectRe: [Patch v2 2/4] dmaengine: tegra: Add Tegra GPC DMA driver
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    Date
    06.08.2020 10:30, Rajesh Gumasta пишет:
    ...
    > +/*
    > + * Save and restore csr and channel register on pm_suspend
    > + * and pm_resume respectively
    > + */
    > +static int __maybe_unused tegra_dma_pm_suspend(struct device *dev)
    > +{
    > + struct tegra_dma *tdma = dev_get_drvdata(dev);
    > + int i;
    > +
    > + for (i = 0; i < tdma->chip_data->nr_channels; i++) {
    > + struct tegra_dma_channel *tdc = &tdma->channels[i];
    > + struct tegra_dma_channel_regs *ch_reg = &tdc->channel_reg;
    > +
    > + ch_reg->csr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_CSR);
    > + ch_reg->src_ptr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR);
    > + ch_reg->dst_ptr = tdc_read(tdc, TEGRA_GPCDMA_CHAN_DST_PTR);
    > + ch_reg->high_addr_ptr = tdc_read(tdc,
    > + TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR);
    > + ch_reg->mc_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MCSEQ);
    > + ch_reg->mmio_seq = tdc_read(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ);
    > + ch_reg->wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_WCOUNT);
    > + }
    > + return 0;
    > +}
    > +
    > +static int __maybe_unused tegra_dma_pm_resume(struct device *dev)
    > +{
    > + struct tegra_dma *tdma = dev_get_drvdata(dev);
    > + int i;
    > +
    > + for (i = 0; i < tdma->chip_data->nr_channels; i++) {
    > + struct tegra_dma_channel *tdc = &tdma->channels[i];
    > + struct tegra_dma_channel_regs *ch_reg = &tdc->channel_reg;
    > +
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_WCOUNT, ch_reg->wcount);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_DST_PTR, ch_reg->dst_ptr);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_SRC_PTR, ch_reg->src_ptr);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_HIGH_ADDR_PTR,
    > + ch_reg->high_addr_ptr);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MMIOSEQ, ch_reg->mmio_seq);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_MCSEQ, ch_reg->mc_seq);
    > + tdc_write(tdc, TEGRA_GPCDMA_CHAN_CSR,
    > + (ch_reg->csr & ~TEGRA_GPCDMA_CSR_ENB));
    > + }
    > + return 0;
    > +}
    > +
    > +static const struct __maybe_unused dev_pm_ops tegra_dma_dev_pm_ops = {
    > + SET_NOIRQ_SYSTEM_SLEEP_PM_OPS(tegra_dma_pm_suspend, tegra_dma_pm_resume)
    > +};

    Please explain why this is needed. All DMA should be stopped (not
    paused) on system's suspend, shouldn't it?

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