RE: [PATCH v17 2/4] dmaengine: tegra: Add tegra gpcdma driver

Akhil R
2022-01-31T04:25:17Z

> 30.01.2022 19:34, Akhil R пишет:
> >> 29.01.2022 19:40, Akhil R пишет:
> >>> +static int tegra_dma_device_pause(struct dma_chan *dc) {
> >>> + struct tegra_dma_channel *tdc = to_tegra_dma_chan(dc);
> >>> + unsigned long wcount, flags;
> >>> + int ret = 0;
> >>> +
> >>> + if (!tdc->tdma->chip_data->hw_support_pause)
> >>> + return 0;
> >>
> >> It's wrong to return zero if pause unsupported, please see what
> >> dmaengine_pause() returns.
> >>
> >>> +
> >>> + spin_lock_irqsave(&tdc->vc.lock, flags);
> >>> + if (!tdc->dma_desc)
> >>> + goto out;
> >>> +
> >>> + ret = tegra_dma_pause(tdc);
> >>> + if (ret) {
> >>> + dev_err(tdc2dev(tdc), "DMA pause timed out\n");
> >>> + goto out;
> >>> + }
> >>> +
> >>> + wcount = tdc_read(tdc, TEGRA_GPCDMA_CHAN_XFER_COUNT);
> >>> + tdc->dma_desc->bytes_xfer +=
> >>> + tdc->dma_desc->bytes_req - (wcount * 4);
> >>
> >> Why transfer is accumulated?
> >>
> >> Why do you need to update xfer size at all on pause?
> >
> > I will verify the calculation. This looks correct only for single sg transaction.
> >
> > Updating xfer_size is added to support drivers which pause the
> > transaction and read the status before terminating.
> > Eg.
>
> Why you couldn't update the status in tegra_dma_terminate_all()?
Is it useful to update the status in terminate_all()? I assume the descriptor
Is freed in vchan_dma_desc_free_list() or am I getting it wrong?

Thanks,
Akhil