Re: [Patch v6 1/4] memory: tegra: Add memory controller channels support

[Ashish Mhetre]

On 4/11/2022 1:05 PM, Dmitry Osipenko wrote:
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>
> On 4/11/22 10:28, Ashish Mhetre wrote:
> > On 4/11/2022 12:03 PM, Dmitry Osipenko wrote:
> > > External email: Use caution opening links or attachments
> > >
> > >
> > > On 4/11/22 09:05, Ashish Mhetre wrote:
> > > > On 4/10/2022 7:48 PM, Dmitry Osipenko wrote:
> > > > > External email: Use caution opening links or attachments
> > > > >
> > > > >
> > > > > 06.04.2022 08:24, Ashish Mhetre пишет:
> > > > > > +     num_dt_channels =
> > > > > > of_property_count_elems_of_size(pdev->dev.of_node, "reg",
> > > > > > +                                                       reg_cells *
> > > > > > sizeof(u32));
> > > > > > +     /*
> > > > > > +      * On tegra186 onwards, memory controller support multiple
> > > > > > channels.
> > > > > > +      * Apart from regular memory controller channels, there is one
> > > > > > broadcast
> > > > > > +      * channel and one for stream-id registers.
> > > > > > +      */
> > > > > > +     if (num_dt_channels < mc->soc->num_channels + 2) {
> > > > > > +             dev_warn(&pdev->dev, "MC channels are missing, please
> > > > > > update memory controller DT node with MC channels\n");
> > > > > > +             return 0;
> > > > > > +     }
> > > > > > +
> > > > > > +     mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev,
> > > > > > "mc-broadcast");
> > > > > > +     if (IS_ERR(mc->bcast_ch_regs))
> > > > > > +             return PTR_ERR(mc->bcast_ch_regs);
> > > > >
> > > > > Looks to me that you don't need to use
> > > > > of_property_count_elems_of_size()
> > > > > and could only check the "mc-broadcast" presence to decide whether this
> > > > > is an older DT.
> > > > Now that we are using reg-names in new DT, yes it'd be fine to just
> > > > check mc-broadcast to decide it's a new or old DT.
> > > >
> > > > > mc->bcast_ch_regs = devm_platform_ioremap_resource_byname(pdev,
> > > > > "broadcast");
> > > > > if (IS_ERR(mc->bcast_ch_regs)) {
> > > > >            dev_warn(&pdev->dev, "Broadcast channel is missing, please
> > > > > update your
> > > > > device-tree\n");
> > > > >            return PTR_ERR(mc->bcast_ch_regs);
> > > > > }
> > > >
> > > > return 0;
> > > >
> > > > to avoid DT ABI break, right?
> > >
> > > Yes, it should be "return 0".
> >
> > But if we "return 0" from here, then what about the case when ioremap()
> > actually fails with new DT i.e. when broadcast reg is present in DT?
> > In that case error should be returned and probe should be failed, right?
>
> You should check for the -ENOENT.

I checked __devm_ioremap_resource(), it returns -EINVAL if given
resource is not present. So should we check for -EINVAL instead?