linux-kernel - Re: [PATCH 4/9] PCI: imx6: Using "linux,pci-domain" as slot ID

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Message-ID: <ZXCmSOwTWR6AVpGB@lizhi-Precision-Tower-5810>
Date:   Wed, 6 Dec 2023 11:50:16 -0500
From:   Frank Li <Frank.li@....com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     imx@...ts.linux.dev, Richard Zhu <hongxing.zhu@....com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rob Herring <robh@...nel.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        "open list:PCI DRIVER FOR IMX6" <linux-pci@...r.kernel.org>,
        "moderated list:PCI DRIVER FOR IMX6" 
        <linux-arm-kernel@...ts.infradead.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/9] PCI: imx6: Using "linux,pci-domain" as slot ID

On Wed, Dec 06, 2023 at 10:36:56AM -0600, Bjorn Helgaas wrote:
> In subject, maybe you mean "Use 'linux,pci-domain' as slot ID"?
> "Using" is the wrong verb form here.
> 
> On Wed, Dec 06, 2023 at 10:58:58AM -0500, Frank Li wrote:
> > Avoid use get slot id by compared with register physical address. If there
> > are more than 2 slots, compared logic will become complex.
> 
> But this doesn't say anything about "linux,pci-domain", and I don't
> see anything about a register physical address in the patch.
> 
> Maybe this commit log was meant for a different patch?  I'm confused.
> 
> > Signed-off-by: Frank Li <Frank.Li@....com>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c b/drivers/pci/controller/dwc/pci-imx6.c
> > index 62d77fabd82a..239ef439ba70 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -33,6 +33,7 @@
> >  #include <linux/pm_domain.h>
> >  #include <linux/pm_runtime.h>
> >  
> > +#include "../../pci.h"
> >  #include "pcie-designware.h"
> >  
> >  #define IMX8MQ_GPR_PCIE_REF_USE_PAD		BIT(9)
> > @@ -1333,6 +1334,11 @@ static int imx6_pcie_probe(struct platform_device *pdev)
> >  					     "Failed to get PCIEPHY reset control\n");
> >  	}
> >  
> > +	/* Using linux,pci-domain as PCI slot id */
> > +	imx6_pcie->controller_id = of_get_pci_domain_nr(node);
> > +	if (imx6_pcie->controller_id)
> > +		imx6_pcie->controller_id = 0;
> 
> I don't understand what this is doing.  It looks the same as just:

Good capture. It should be 
if (imx6_pcie->controller_id < 0)
	imx6_pcie->controller_id = 0;

for only one PCI controller case. I just tested first one slot before send
patch, so not met problem.

Previously, we use below logic
	if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
		imx6_pcie->controller_id = 1;

It is not good to depend on register's base address. If there are 3
controllers, check logic will becomoe ugly.

Frank
> 
>   imx6_pcie->controller_id = 0;
> 
> Maybe this is a typo?  As written, it doesn't look like there's any
> point in calling of_get_pci_domain_nr().
> 
> >  	switch (imx6_pcie->drvdata->variant) {
> >  	case IMX7D:
> >  		if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
> > -- 
> > 2.34.1
> >