Re: [PATCH v9 1/4] i2c: tegra: Do not configure DMA if not supported

[Jon Hunter]

On 28/10/2025 13:08, Akhil R wrote:
> On Tue, 28 Oct 2025 10:41:54 +0000 Jon Hunter wrote:
> > On 28/10/2025 10:00, Akhil R wrote:
> > > On Fri, 24 Oct 2025 16:20:09 +0100, Jon Hunter wrote:
> > > > On 01/10/2025 07:47, Kartik Rajput wrote:
>
> ...
>
> > > > > diff --git a/drivers/i2c/busses/i2c-tegra.c b/drivers/i2c/busses/i2c-tegra.c
> > > > > index e533460bccc3..aa7c0d8c0941 100644
> > > > > --- a/drivers/i2c/busses/i2c-tegra.c
> > > > > +++ b/drivers/i2c/busses/i2c-tegra.c
> > > > > @@ -449,6 +449,11 @@ static int tegra_i2c_init_dma(struct tegra_i2c_dev *i2c_dev)
> > > > >          if (IS_VI(i2c_dev))
> > > > >                  return 0;
> > > > >   
> > > > > +     if (!of_property_present(i2c_dev->dev->of_node, "dmas")) {
> > > > > +             dev_dbg(i2c_dev->dev, "DMA not available, falling back to PIO\n");
> > > > > +             return 0;
> > > > > +     }
> > > > > +
> > > > >          if (i2c_dev->hw->has_apb_dma) {
> > > > >                  if (!IS_ENABLED(CONFIG_TEGRA20_APB_DMA)) {
> > > > >                          dev_dbg(i2c_dev->dev, "APB DMA support not enabled\n");
> > > >
> > > > What about ACPI based devices?
> > >
> > > The of_ function returns false if using ACPI. Since these DMA drivers does
> > > not support ACPI enumeration currently, we would not require to proceed
> > > further anyway. But if required we can add an additional check with
> > > acpi_dma_supported() or similar. Do you suggest adding a check for ACPI?
> >
> > I was just wondering if it is better to use fwnode_property_present()
> > instead.
>
> I think ACPI does not use 'dmas' property to connect a DMA resource.
> It uses FixedDMA or something similar. It may not be helpful to use
> fwnode_*() or device_*() check here in that case.

OK. Then fine to leave this as-is.

Jon

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