Re: [PATCH] memory: tegra: add multi-socket support to the memory interconnect

[Thierry Reding <thierry.reding@kernel.org>]

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On Wed, May 27, 2026 at 04:46:38PM +0200, Krzysztof Kozlowski wrote:
> On 27/05/2026 16:21, Sumit Gupta wrote:
> > 
> > On 27/05/26 18:25, Krzysztof Kozlowski wrote:
> >> External email: Use caution opening links or attachments
> >>
> >>
> >> On 21/05/2026 16:05, Sumit Gupta wrote:
> >>> -             err = icc_link_create(node, TEGRA_ICC_MC);
> >>> +             err = tegra_mc_icc_link_create(node, node_id, TEGRA_ICC_MC);
> >>>                if (err)
> >>>                        goto remove_nodes;
> >>>
> >>> @@ -957,7 +969,13 @@ static int tegra_mc_probe(struct platform_device *pdev)
> >>>        if (IS_ERR(mc->regs))
> >>>                return PTR_ERR(mc->regs);
> >>>
> >>> -     mc->debugfs.root = debugfs_create_dir("mc", NULL);
> >>> +     if (!mc_debugfs_root)
> >> That's a probe path and you created a singletone. Looks like preventing
> >> async probing for no real reason.
> >>
> >> I am very against singletons and debugfs does not look like justified
> >> exception.
> > 
> > The singleton was added so multi-socket MC/EMC instances could
> > share a "mc"/"emc" parent. I'll drop it in v2.
> > 
> > On single-socket SoCs, the "mc"/"emc" names will be unchanged.
> > On multi-socket SoCs, each instance will create a top-level debugfs
> > dir named with dev_name(). Same pattern in tegra186-emc.c.
> > 
> >    if (dev_to_node(mc->dev) == NUMA_NO_NODE)
> >        mc->debugfs.root = debugfs_create_dir("mc", NULL);
> >    else
> >        mc->debugfs.root = debugfs_create_dir(dev_name(mc->dev), NULL);
> 
> You assume this is fully synced, so you as well could do a look up and
> then use what you found or create new dir. If you think that is racy, so
> is this approach... How are other drivers handling per-device debugfs
> directories? Do they also create such in the top-level? I think no.

I think we want a top-level directory for a bit more structure in
debugfs. But I also think we want to create that top-level directory in
the module's init function rather than _probe. Granted, that means we
can't use any of those helper macros, but we don't use that for the MC
driver anyway.

Thierry

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