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

[Bjorn Helgaas <helgaas@kernel.org>]

On Thu, Mar 13, 2025 at 09:54:25AM +0100, Lucas Stach wrote:
> Am Mittwoch, dem 12.03.2025 um 10:22 -0400 schrieb Frank Li:
> > On Wed, Mar 12, 2025 at 09:28:02AM +0100, Lucas Stach wrote:
> > > Am Mittwoch, dem 12.03.2025 um 04:05 +0000 schrieb Hongxing Zhu:
> > > > > -----Original Message-----
> > > > > From: Bjorn Helgaas <helgaas@kernel.org>
> > > > > Sent: 2025年3月11日 23:55
> > > > > 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 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?
> > > > > >
> > > > > > 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.
> > > >
> > > > How about the following updates of the commit log?
> > > > 
> > > > Use the domain number replace the hardcodes to uniquely
> > > > identify different controller on i.MX8MQ platforms. No
> > > > function changes.  Please make sure the " linux,pci-domain" is
> > > > set for i.MX8MQ correctly, since  the controller id is relied
> > > > on it totally.
> > > > 
> > > This breaks running a new kernel on an old DT without the
> > > linux,pci-domain property, which I'm absolutely no fan of. We
> > > tried really hard to keep this way around working in the i.MX
> > > world.
> > 
> > 8MQ already add linux,pci-domain since Jan, 2021
> > 
> > commit c0b70f05c87f3b09b391027c6f056d0facf331ef
> > Author: Peng Fan <peng.fan@nxp.com>
> > Date:   Fri Jan 15 11:26:57 2021 +0800
> > 
> > Only missed is pcie-ep side, which have not been used at all boards dts
> > file in upstream.
> 
> I wasn't aware of this. 2021 is quite a while ago, so I suspect that
> nobody is going to run a new kernel with a DT this old. I retract my
> objection.

Sounds good, thanks, Lucas.  We really do want to avoid breaking old
DTs, so I appreciate your highlighting of it.  Even if we believe none
of them will break, I think it's worth mentioning the
'linux,pci-domain' dependency and the commit that added it to the
.dtsi in the commit log.

Bjorn