Re: [PATCH 3/4] PCI: cadence-ep: Introduce cdns_pcie_ep_disable helper for cleanup

[Siddharth Vadapalli <s-vadapalli@ti.com>]

On Wed, Mar 19, 2025 at 04:02:17PM +0530, Manivannan Sadhasivam wrote:
> On Tue, Mar 18, 2025 at 01:42:39PM +0530, Siddharth Vadapalli wrote:
> > On Tue, Mar 18, 2025 at 01:33:04PM +0530, Manivannan Sadhasivam wrote:
> > 
> > Hello Mani,
> > 
> > > On Fri, Mar 07, 2025 at 04:01:27PM +0530, Siddharth Vadapalli wrote:
> > > > Introduce the helper function cdns_pcie_ep_disable() which will undo the
> > > > configuration performed by cdns_pcie_ep_setup(). Also, export it for use
> > > > by the existing callers of cdns_pcie_ep_setup(), thereby allowing them
> > > > to cleanup on their exit path.
> > > > 
> > > > Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
> > > > ---
> > > >  drivers/pci/controller/cadence/pcie-cadence-ep.c | 10 ++++++++++
> > > >  drivers/pci/controller/cadence/pcie-cadence.h    |  5 +++++
> > > >  2 files changed, 15 insertions(+)
> > > > 
> > > > diff --git a/drivers/pci/controller/cadence/pcie-cadence-ep.c b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> > > > index eeb2afdd223e..85bec57fa5d9 100644
> > > > --- a/drivers/pci/controller/cadence/pcie-cadence-ep.c
> > > > +++ b/drivers/pci/controller/cadence/pcie-cadence-ep.c
> > > > @@ -646,6 +646,16 @@ static const struct pci_epc_ops cdns_pcie_epc_ops = {
> > > >  	.get_features	= cdns_pcie_ep_get_features,
> > > >  };
> > > >  
> > > > +void cdns_pcie_ep_disable(struct cdns_pcie_ep *ep)
> > > > +{
> > > > +	struct device *dev = ep->pcie.dev;
> > > > +	struct pci_epc *epc = to_pci_epc(dev);
> > > > +
> > > 
> > > pci_epc_deinit_notify()
> > 
> > I had initially planned to add this, but I noticed that it is not
> > invoked by dw_pcie_ep_deinit() within
> > drivers/pci/controller/dwc/pcie-designware-ep.c
> > Since cdns_pcie_ep_disable() is similar to dw_pcie_ep_deinit(), I
> > decided to drop it. Current callers of pci_epc_deinit_notify() are:
> > drivers/pci/controller/dwc/pcie-qcom-ep.c
> > drivers/pci/controller/dwc/pcie-tegra194.c
> > while there are many more users of dw_pcie_ep_deinit() that don't invoke
> > pci_epc_deinit_notify().
> > 
> > While I don't intend to justify dropping pci_epc_deinit_notify() in the
> > cleanup path, I wanted to check if this should be added to
> > dw_pcie_ep_deinit() as well. Or is it the case that dw_pcie_ep_deinit()
> > is different from cdns_pcie_ep_disable()? Please let me know.
> > 
> 
> Reason why it was not added to dw_pcie_ep_deinit() because, deinit_notify() is
> supposed to be called while performing the resource cleanup with active refclk.
> 
> Some plaforms (Tegra, Qcom) depend on refclk from host. So if deinit_notify() is
> called when there is no refclk, it will crash the endpoint SoC. But since
> cadence endpoint platforms seem to generate their own refclk, you can call
> deinit_notify() during deinit phase.

Thank you for the clarification. I will add pci_epc_deinit_notify() to
cdns_pcie_ep_disable() in the v2 series.

Regards,
Siddharth.