Re: [PATCH V10 03/13] PCI: dwc: Parse Root Port nodes in dw_pcie_host_init()

[Manivannan Sadhasivam]

On Tue, Apr 07, 2026 at 03:21:30AM +0000, Sherry Sun wrote:
> > On Thu, Apr 02, 2026 at 05:50:57PM +0800, Sherry Sun wrote:
> > > Add support for parsing Root Port child nodes in dw_pcie_host_init()
> > > using pci_host_common_parse_ports(). This allows DWC-based drivers to
> > > specify Root Port properties (like reset GPIOs) in individual Root
> > > Port nodes rather than in the host bridge node.
> > >
> > > Signed-off-by: Sherry Sun <sherry.sun@xxxxxxx>
> > > ---
> > >  drivers/pci/controller/dwc/pcie-designware-host.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > index da152c31bb2e..f6fca984fb34 100644
> > > --- a/drivers/pci/controller/dwc/pcie-designware-host.c
> > > +++ b/drivers/pci/controller/dwc/pcie-designware-host.c
> > > @@ -20,6 +20,7 @@
> > >  #include <linux/platform_device.h>
> > >
> > >  #include "../../pci.h"
> > > +#include "../pci-host-common.h"
> > >  #include "pcie-designware.h"
> > >
> > >  static struct pci_ops dw_pcie_ops;
> > > @@ -581,6 +582,13 @@ int dw_pcie_host_init(struct dw_pcie_rp *pp)
> > >
> > >  	pp->bridge = bridge;
> > >
> > > +	/* Parse Root Port nodes if present */
> > > +	ret = pci_host_common_parse_ports(dev, bridge);
> > > +	if (ret && ret != -ENOENT) {
> > > +		dev_err(dev, "Failed to parse Root Port nodes: %d\n", ret);
> > > +		return ret;
> > 
> > Won't this change break drivers that parse Root Ports on their own? Either
> > you need to modify them also in this change or call this API from imx6 driver
> > and let other drivers switch to it in a phased manner.
> > 
> > I perfer the latter.
> 
> Hi Mani, sorry I didn't fully get your point here, there are no changes to this part
> V10, for drivers that parse Root Ports on their own, here pci_host_common_parse_ports()
> will return -ENOENT, so nothing break as we discussed this in V8
> https://lore.kernel.org/all/dcl3bdljrdzgeaybrg3dc5uaxkebkjns7pajix6mxxftao5g4m@vm3ywyyp4ujh/.
> 

So if this API gets called first, it will acquire PERST# from the Root Port node
and if the controller drivers try to do the same in their own parsing code,
PERST# request will return -EBUSY and the probe will fail.

On the other hand, if the controller drivers parse PERST# first, this API will
return -EBUSY and will result in probe failure.

Only way to fix this issue would be to call this API from imx6 driver for now
and start migrating other drivers later.

- Mani

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