linux-kernel - Re: [PATCH 3/4] powerpc/pseries/iommu: Move window-removing part of remove_ddw into remove_dma

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Date:   Tue, 23 Jun 2020 11:33:03 +1000
From:   "Oliver O'Halloran" <oohall@...il.com>
To:     Alexey Kardashevskiy <aik@...abs.ru>
Cc:     Leonardo Bras <leobras.c@...il.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>,
        Ram Pai <linuxram@...ibm.com>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] powerpc/pseries/iommu: Move window-removing part of
 remove_ddw into remove_dma_window

On Tue, Jun 23, 2020 at 11:12 AM Alexey Kardashevskiy <aik@...abs.ru> wrote:
>
> On 23/06/2020 04:59, Leonardo Bras wrote:
> >
> >> Also, despite this particular file, the "pdn" name is usually used for
> >> struct pci_dn (not device_node), let's keep it that way.
> >
> > Sure, I got confused for some time about this, as we have:
> > static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn).
> > but on *_ddw() we have "struct pci_dn *pdn".
>
> True again, not the cleanest style here.
>
>
> > I will also add a patch that renames those 'struct device_node *pdn' to
> > something like 'struct device_node *parent_dn'.

I usually go with "np" or "node". In this case I'd use "parent_np" or
just "parent." As you said pci_dn conventionally uses pdn so that
should be avoided if at all possible. There's some places that just
use "dn" for device_node, but I don't think that's something we should
encourage due to how similar it is to pdn.

> I would not go that far, we (well, Oliver) are getting rid of many
> occurrences of pci_dn and Oliver may have a stronger opinion here.

I'm trying to remove the use of pci_dn from non-RTAS platforms which
doesn't apply to pseries. For RTAS platforms having pci_dn sort of
makes sense since it's used to cache data from the device_node and
having it saves you from needing to parse and validate the DT at
runtime since we're supposed to be relying on the FW provided settings
in the DT. I want to get rid of it on PowerNV because it's become a
dumping ground for random bits and pieces of platform specific data.
It's confusing at best and IMO it duplicates a lot of what's already
available in the per-PHB structures which the platform specific stuff
should actually be looking at.

Oliver