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

[Manivannan Sadhasivam]

On Tue, Apr 07, 2026 at 09:18:58AM +0000, Sherry Sun wrote:
> > 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.ke/
> > rnel.org%2Fall%2Fdcl3bdljrdzgeaybrg3dc5uaxkebkjns7pajix6mxxftao5g4m%40
> > vm3ywyyp4ujh%2F&data=05%7C02%7Csherry.sun%40nxp.com%7Cd9faef64b
> > 8154bdbc6ee08de94724b22%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%
> > 7C0%7C639111415791802118%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1
> > hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIl
> > dUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=POsurqr9RqBCnaQyeXDK2HQTN
> > a4Nc0tfl7thSiM9qHA%3D&reserved=0.
> > >
> >
> > 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.
> >
> 
> Ok, get your point here. Your assumption is based on the premise that the controller
> driver parse the reset-gpios in the Root Port node, not that most controller drivers
> now use reset under the host bridge node. For reset-gpios in the Root Port node,
> they should eventually switch to this common API.
> 

Not many, but still some and it is paramount to not regress them. That's my
point.

> Anyway, I will call this API in imx6 driver at this stage to avoid impact other platforms.
> 

Sounds good!

- Mani

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