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

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Date:   Mon, 22 Jun 2020 23:26:18 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Oliver O'Halloran <oohall@...il.com>,
        Alexey Kardashevskiy <aik@...abs.ru>
Cc:     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, 2020-06-23 at 11:33 +1000, Oliver O'Halloran wrote:
> 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.

Sure, I will try that.

> 
> > 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

Best regards,
Leonardo Bras