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

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Date:   Tue, 31 Aug 2021 11:31:24 +0800
From:   Chuanjia Liu <chuanjia.liu@...iatek.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     <robh+dt@...nel.org>, <bhelgaas@...gle.com>,
        <matthias.bgg@...il.com>, <lorenzo.pieralisi@....com>,
        <ryder.lee@...iatek.com>, <jianjun.wang@...iatek.com>,
        <yong.wu@...iatek.com>, <linux-pci@...r.kernel.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.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, 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;

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)
      return PTR_ERR(regmap);

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().

Thanks
Chuanjia