linux-kernel - RE: [PATCH 2/4] PCI: dwc: Return directly when num-lanes is not found

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Date:   Tue, 13 Aug 2019 03:13:04 +0000
From:   "Z.q. Hou" <zhiqiang.hou@....com>
To:     Andrew Murray <andrew.murray@....com>
CC:     "linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "gustavo.pimentel@...opsys.com" <gustavo.pimentel@...opsys.com>,
        "jingoohan1@...il.com" <jingoohan1@...il.com>,
        "bhelgaas@...gle.com" <bhelgaas@...gle.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        Leo Li <leoyang.li@....com>,
        "lorenzo.pieralisi@....com" <lorenzo.pieralisi@....com>,
        "M.h. Lian" <minghuan.lian@....com>
Subject: RE: [PATCH 2/4] PCI: dwc: Return directly when num-lanes is not found

Hi Andrew,

Thanks a lot for your review!

B.R,
Zhiqiang

> -----Original Message-----
> From: Andrew Murray <andrew.murray@....com>
> Sent: 2019年8月12日 16:34
> To: Z.q. Hou <zhiqiang.hou@....com>
> Cc: linux-pci@...r.kernel.org; devicetree@...r.kernel.org;
> linux-kernel@...r.kernel.org; gustavo.pimentel@...opsys.com;
> jingoohan1@...il.com; bhelgaas@...gle.com; robh+dt@...nel.org;
> mark.rutland@....com; shawnguo@...nel.org; Leo Li
> <leoyang.li@....com>; lorenzo.pieralisi@....com; M.h. Lian
> <minghuan.lian@....com>
> Subject: Re: [PATCH 2/4] PCI: dwc: Return directly when num-lanes is not
> found
> 
> On Mon, Aug 12, 2019 at 04:22:22AM +0000, Z.q. Hou wrote:
> > From: Hou Zhiqiang <Zhiqiang.Hou@....com>
> >
> > The num-lanes is optional, so probably it isn't added on some
> > platforms. The subsequent programming is base on the num-lanes, hence
> > return when it is not found.
> >
> > Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@....com>
> > ---
> >  drivers/pci/controller/dwc/pcie-designware.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pcie-designware.c
> > b/drivers/pci/controller/dwc/pcie-designware.c
> > index 7d25102c304c..0a89bfd1636e 100644
> > --- a/drivers/pci/controller/dwc/pcie-designware.c
> > +++ b/drivers/pci/controller/dwc/pcie-designware.c
> > @@ -423,8 +423,10 @@ void dw_pcie_setup(struct dw_pcie *pci)
> >
> >
> >  	ret = of_property_read_u32(np, "num-lanes", &lanes);
> > -	if (ret)
> > -		lanes = 0;
> > +	if (ret) {
> > +		dev_dbg(pci->dev, "property num-lanes isn't found\n");
> > +		return;
> > +	}
> 
> The existing code would assign a value of 0 to lanes when num-lanes isn't
> specified, however this value isn't supported by the following switch
> statement - thus we'd also print an error and return.
> 
> Therefore the only and subtle effect effect of this patch is to change a
> dev_err to a dev_dbg when num-lanes isn't specified and avoid a read of
> PCIE_PORT_LINK_CONTROL.
> 
> Given that num-lanes is described as optional this makes perfect sense.
> Though the commit message/hunk does give the apperance that this
> provides a more functional change.
> 
> Anyway:
> 
> Reviewed-by: Andrew Murray <andrew.murray@....com>
> 
> 
> >
> >  	/* Set the number of lanes */
> >  	val = dw_pcie_readl_dbi(pci, PCIE_PORT_LINK_CONTROL);
> > --
> > 2.17.1
> >