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

Akhil R
2022-01-30T16:34:24Z

> 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. https://elixir.bootlin.com/linux/latest/source/drivers/tty/serial/amba-pl011.c

Thanks,
Akhil