linux-kernel - Re: [PATCH v12 2/6] PCI: mediatek: Add new method to get shared pcie-cfg base address

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Message-ID: <CAL_Jsq+dBi-XUDJD_STP=jWw+RLkRpX1U9XsRMhqK4U1H=0FHw@mail.gmail.com>
Date:   Tue, 31 Aug 2021 10:17:53 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Chuanjia Liu <chuanjia.liu@...iatek.com>
Cc:     Bjorn Helgaas <helgaas@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
        Ryder Lee <ryder.lee@...iatek.com>,
        Jianjun Wang <jianjun.wang@...iatek.com>,
        Yong Wu <yong.wu@...iatek.com>,
        PCI <linux-pci@...r.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>, devicetree@...r.kernel.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v12 2/6] PCI: mediatek: Add new method to get shared
 pcie-cfg base address

On Mon, Aug 30, 2021 at 10:31 PM Chuanjia Liu <chuanjia.liu@...iatek.com> wrote:
>
> On Mon, 2021-08-30 at 16:43 -0500, Bjorn Helgaas wrote:
> > On Mon, Aug 30, 2021 at 03:09:44PM +0800, Chuanjia Liu wrote:
> > > On Fri, 2021-08-27 at 11:46 -0500, Bjorn Helgaas wrote:
> > > > On Mon, Aug 23, 2021 at 11:27:56AM +0800, Chuanjia Liu wrote:
> > > > > @@ -995,6 +1004,14 @@ static int mtk_pcie_subsys_powerup(struct
> > > > > mtk_pcie *pcie)
> > > > >                         return PTR_ERR(pcie->base);
> > > > >         }
> > > > >
> > > > > +       cfg_node = of_find_compatible_node(NULL, NULL,
> > > > > +                                          "mediatek,generic-
> > > > > pciecfg");
> > > > > +       if (cfg_node) {
> > > > > +               pcie->cfg = syscon_node_to_regmap(cfg_node);
> > > >
> > > > Other drivers in drivers/pci/controller/ use
> > > > syscon_regmap_lookup_by_phandle() (j721e, dra7xx, keystone,
> > > > layerscape, artpec6) or syscon_regmap_lookup_by_compatible()
> > > > (imx6,
> > > > kirin, v3-semi).
> > > >
> > > > You should do it the same way unless there's a need to be
> > > > different.
> > >
> > > I have used phandle, but Rob suggested to search for the node by
> > > compatible.
> > > The reason why syscon_regmap_lookup_by_compatible() is not
> > > used here is that the pciecfg node is optional, and there is no
> > > need to
> > > return error when the node is not searched.
> >
> > How about this?
> >
> >   regmap = syscon_regmap_lookup_by_compatible("mediatek,generic-
> > pciecfg");
> >   if (!IS_ERR(regmap))
> >     pcie->cfg = regmap;

+1

>
> Hi Bjorn,
>
> We need to deal with three situations
> 1) No error
> 2) The error of the node not found, don't do anything
> 3) Other errors, return errors
>
> I guess you mean
>
> regmap = syscon_regmap_lookup_by_compatible("mediatek,generic-
> pciecfg");
>   if (!IS_ERR(regmap))
>       pcie->cfg = regmap;
>   else if (IS_ERR(regmap) && PTR_ERR(regmap) != -ENODEV)

You already know  IS_ERR is true here.

>       return PTR_ERR(regmap);

syscon_regmap_lookup_by_compatible_optional is the function you are
looking for. The _optional flavor doesn't exist, so create it. There
is one for the phandle lookup.

>
> I'm not sure if we need this, it seems a little weird and there are
> many drivers in other subsystems that use syscon_node_to_regmap().

You are implementing the exact same sequence that
syscon_regmap_lookup_by_compatible() does, so clearly you should be
using it. The one difference is you forgot the of_node_put().

Rob