Hi Miquel,
On Thu, Feb 24, 2022 at 12:36 PM Miquel Raynal
<miquel.raynal@xxxxxxxxxxx> wrote:
> > > > > > > +static int rzn1_dmamux_probe(struct platform_device *pdev)
> > > > > > > +{
> > > > > > > + struct device_node *mux_node = pdev->dev.of_node;
> > > > > > > + const struct of_device_id *match;
> > > > > > > + struct device_node *dmac_node;
> > > > > > > + struct rzn1_dmamux_data *dmamux;
> > > > > > > +
> > > > > > > + dmamux = devm_kzalloc(&pdev->dev, sizeof(*dmamux), GFP_KERNEL);
> > > > > > > + if (!dmamux)
> > > > > > > + return -ENOMEM;
> > > > > > > +
> > > > > > > + mutex_init(&dmamux->lock);
> > > > > > > +
> > > > > > > + dmac_node = of_parse_phandle(mux_node, "dma-masters", 0);
> > > > > > > + if (!dmac_node)
> > > > > > > + return dev_err_probe(&pdev->dev, -ENODEV, "Can't get DMA master node\n");
> > > > > > > +
> > > > > > > + match = of_match_node(rzn1_dmac_match, dmac_node);
> > > > > > > + if (!match) {
> > > > > > > + of_node_put(dmac_node);
> > > > > > > + return dev_err_probe(&pdev->dev, -EINVAL, "DMA master is not supported\n");
> > > > > > > + }
> > > > > > > +
> > > > > > > + if (of_property_read_u32(dmac_node, "dma-requests", &dmamux->dmac_requests)) {
> > > > > > > + of_node_put(dmac_node);
> > > > > > > + return dev_err_probe(&pdev->dev, -EINVAL, "Missing DMAC requests information\n");
> > > > > > > + }
> > > > > > > +
> > > > > > > + of_node_put(dmac_node);
> > > > > >
> > > > > > When hardcoding dmac_requests to 16, I guess the whole dmac_node
> > > > > > handling can be removed?
> > > > >
> > > > > Not really, I think the following checks are still valid and fortunate,
> > > > > and they need some of_ handling to work properly:
> > > > > - verify that the chan requested is within the range of dmac_requests
> > > > > in the _route_allocate() callback
> > > > > - ensure the dmamux is wired to a supported DMAC in the DT (this
> > > > > condition might be loosen in the future if needed or dropped entirely
> > > > > if considered useless)
> > > > > - I would like to add a check against the number of requests supported
> > > > > by the dmamux and the dmac (not done yet).
> > > > > For the record, I've taken inspiration to write these lines on the other
> > > > > dma router driver from TI.
>
> ^^^^^^^^^^^
> ... these checks
I don't know. Some of them will be checked when calling into the
parent DMAC, right?
>
> > > > >
> > > > > Unless, and I know some people think like that, we do not try to
> > > > > validate the DT and if the DT is wrong that is none of our business.
> > > > >
> > > > > >
> > > > > > > +
> > > > > > > + if (of_property_read_u32(mux_node, "dma-requests", &dmamux->dmamux_requests)) {
> > > > > >
> > > > > > Don't obtain from DT, but fix to 32?
> > > > >
> > > > > I believe the answer to the previous question should give me a clue
> > > > > about why you would prefer hardcoding than reading from the DT such
> > > > > an information. Perhaps I should mention that all these properties are
> > > > > already part of the bindings, and are not specific to the driver, the
> > > > > information will be in the DT anyway.
> > > >
> > > > The 32 is a property of the hardware (32 bits in DMAMUX register).
> > > > So IMHO it falls under the "differentiate by compatible value,
> > > > not by property" rule.
> > >
> > > I agree this is a property of the hardware and feels redundant here.
> > >
> > > What about the checks below, do you agree with the fact that I should
> > > keep them or do you prefer dropping them (all? partially?)?
> >
> > There are no checks below?
>
> I meant above /o\ ...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
