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

[Bjorn Helgaas <helgaas@kernel.org>]

On Tue, Mar 11, 2025 at 01:11:04AM +0000, Hongxing Zhu wrote:
> > -----Original Message-----
> > From: Bjorn Helgaas <helgaas@kernel.org>
> > Sent: 2025年3月10日 23:11
> > To: Hongxing Zhu <hongxing.zhu@nxp.com>
> > Cc: robh@kernel.org; krzk+dt@kernel.org; conor+dt@kernel.org;
> > shawnguo@kernel.org; l.stach@pengutronix.de; lpieralisi@kernel.org;
> > kw@linux.com; manivannan.sadhasivam@linaro.org; bhelgaas@google.com;
> > s.hauer@pengutronix.de; festevam@gmail.com; devicetree@vger.kernel.org;
> > linux-pci@vger.kernel.org; imx@lists.linux.dev; kernel@pengutronix.de;
> > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org
> > 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@nxp.com>
> > > ---
> > >  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.

Great, thanks!  Maybe we can amend the commit log to mention that and
the new "linux,pci-domain" dependency.