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

[Z.q. Hou]

Hi Andrew,

Thanks a lot for your review!

B.R,
Zhiqiang

> -----Original Message-----
> From: Andrew Murray <andrew.murray@xxxxxxx>
> Sent: 2019年8月12日 16:34
> To: Z.q. Hou <zhiqiang.hou@xxxxxxx>
> Cc: linux-pci@xxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-kernel@xxxxxxxxxxxxxxx; gustavo.pimentel@xxxxxxxxxxxx;
> jingoohan1@xxxxxxxxx; bhelgaas@xxxxxxxxxx; robh+dt@xxxxxxxxxx;
> mark.rutland@xxxxxxx; shawnguo@xxxxxxxxxx; Leo Li
> <leoyang.li@xxxxxxx>; lorenzo.pieralisi@xxxxxxx; M.h. Lian
> <minghuan.lian@xxxxxxx>
> 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@xxxxxxx>
> >
> > 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@xxxxxxx>
> > ---
> >  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@xxxxxxx>
> 
> 
> >
> >  	/* Set the number of lanes */
> >  	val = dw_pcie_readl_dbi(pci, PCIE_PORT_LINK_CONTROL);
> > --
> > 2.17.1
> >