RE: [PATCH v1 2/2] PCI: imx6: Use domain number replace the hardcodes

[Hongxing Zhu]

> -----Original Message-----
> From: Bjorn Helgaas <helgaas@xxxxxxxxxx>
> Sent: 2025年3月10日 23:11
> To: Hongxing Zhu <hongxing.zhu@xxxxxxx>
> Cc: robh@xxxxxxxxxx; krzk+dt@xxxxxxxxxx; conor+dt@xxxxxxxxxx;
> shawnguo@xxxxxxxxxx; l.stach@xxxxxxxxxxxxxx; lpieralisi@xxxxxxxxxx;
> kw@xxxxxxxxx; manivannan.sadhasivam@xxxxxxxxxx; bhelgaas@xxxxxxxxxx;
> s.hauer@xxxxxxxxxxxxxx; festevam@xxxxxxxxx; devicetree@xxxxxxxxxxxxxxx;
> linux-pci@xxxxxxxxxxxxxxx; imx@xxxxxxxxxxxxxxx; kernel@xxxxxxxxxxxxxx;
> linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH v1 2/2] PCI: imx6: Use domain number replace the
> hardcodes
> 
> On Wed, Feb 26, 2025 at 10:42:56AM +0800, Richard Zhu wrote:
> > Use the domain number replace the hardcodes to uniquely identify
> > different controller on i.MX8MQ platforms. No function changes.
> >
> > Signed-off-by: Richard Zhu <hongxing.zhu@xxxxxxx>
> > ---
> >  drivers/pci/controller/dwc/pci-imx6.c | 14 ++++++--------
> >  1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/pci/controller/dwc/pci-imx6.c
> > b/drivers/pci/controller/dwc/pci-imx6.c
> > index 90ace941090f..ab9ebb783593 100644
> > --- a/drivers/pci/controller/dwc/pci-imx6.c
> > +++ b/drivers/pci/controller/dwc/pci-imx6.c
> > @@ -41,7 +41,6 @@
> >  #define IMX8MQ_GPR_PCIE_CLK_REQ_OVERRIDE	BIT(11)
> >  #define IMX8MQ_GPR_PCIE_VREG_BYPASS		BIT(12)
> >  #define IMX8MQ_GPR12_PCIE2_CTRL_DEVICE_TYPE	GENMASK(11, 8)
> > -#define IMX8MQ_PCIE2_BASE_ADDR			0x33c00000
> >
> >  #define IMX95_PCIE_PHY_GEN_CTRL			0x0
> >  #define IMX95_PCIE_REF_USE_PAD			BIT(17)
> > @@ -1474,7 +1473,6 @@ static int imx_pcie_probe(struct platform_device
> *pdev)
> >  	struct dw_pcie *pci;
> >  	struct imx_pcie *imx_pcie;
> >  	struct device_node *np;
> > -	struct resource *dbi_base;
> >  	struct device_node *node = dev->of_node;
> >  	int i, ret, req_cnt;
> >  	u16 val;
> > @@ -1515,10 +1513,6 @@ static int imx_pcie_probe(struct
> platform_device *pdev)
> >  			return PTR_ERR(imx_pcie->phy_base);
> >  	}
> >
> > -	pci->dbi_base = devm_platform_get_and_ioremap_resource(pdev, 0,
> &dbi_base);
> > -	if (IS_ERR(pci->dbi_base))
> > -		return PTR_ERR(pci->dbi_base);
> 
> This makes me wonder.
> 
> IIUC this means that previously we set controller_id to 1 if the first item in
> devicetree "reg" was 0x33c00000, and now we will set controller_id to 1 if
> the devicetree "linux,pci-domain" property is 1.
> This is good, but I think this new dependency on the correct
> "linux,pci-domain" in devicetree should be mentioned in the commit log.
> 
> My bigger worry is that we no longer set pci->dbi_base at all.  I see that the
> only use of pci->dbi_base in pci-imx6.c was to determine the controller_id,
> but this is a DWC-based driver, and the DWC core certainly uses
> pci->dbi_base.  Are we sure that none of those DWC core paths are
> important to pci-imx6.c?
Hi Bjorn:
Thanks for your concerns.
Don't worry about the assignment of pci->dbi_base.
If pci-imx6.c driver doesn't set it. DWC core driver would set it when
 dw_pcie_get_resources() is invoked.

dw_pcie_host_init()/dw_pcie_ep_init()
  ->dw_pcie_get_resources()

...
        if (!pci->dbi_base) {
                res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "dbi");
                pci->dbi_base = devm_pci_remap_cfg_resource(pci->dev, res);
                if (IS_ERR(pci->dbi_base))
                        return PTR_ERR(pci->dbi_base);
                pci->dbi_phys_addr = res->start;
        }
...


Best Regards
Richard Zhu
> 
> >  	/* Fetch GPIOs */
> >  	imx_pcie->reset_gpiod = devm_gpiod_get_optional(dev, "reset",
> GPIOD_OUT_HIGH);
> >  	if (IS_ERR(imx_pcie->reset_gpiod))
> > @@ -1565,8 +1559,12 @@ static int imx_pcie_probe(struct
> platform_device *pdev)
> >  	switch (imx_pcie->drvdata->variant) {
> >  	case IMX8MQ:
> >  	case IMX8MQ_EP:
> > -		if (dbi_base->start == IMX8MQ_PCIE2_BASE_ADDR)
> > -			imx_pcie->controller_id = 1;
> > +		ret = of_get_pci_domain_nr(node);
> > +		if (ret < 0 || ret > 1)
> > +			return dev_err_probe(dev, -ENODEV,
> > +					     "failed to get valid pcie domain\n");
> > +		else
> > +			imx_pcie->controller_id = ret;
> >  		break;
> >  	default:
> >  		break;
> > --
> > 2.37.1
> >