linux-kernel - Re: [PATCH] PCI: endpoint: Don't stop EP controller by EP function

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Date:   Tue, 5 Jul 2022 22:08:12 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Shunsuke Mie <mie@...l.co.jp>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Hou Zhiqiang <Zhiqiang.Hou@....com>,
        Li Chen <lchen@...arella.com>, linux-pci@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: endpoint: Don't stop EP controller by EP function

On Wed, Jul 06, 2022 at 11:37:29AM +0900, Shunsuke Mie wrote:
> 2022年7月6日(水) 7:40 Bjorn Helgaas <helgaas@...nel.org>:
> > On Wed, Jun 22, 2022 at 01:09:24PM +0900, Shunsuke Mie wrote:
> > > For multi-function endpoint device, an ep function shouldn't stop EP
> > > controller. Nomally the controller is stopped via configfs.
> >
> > Can you please clarify this for me?
> >
> > An endpoint function by itself wouldn't stop an endpoint controller.
> > I assume that some *operation* on an endpoint function currently stops
> > the endpoint controller, but that operation should not stop the
> > controller?
> >
> > I guess the operation is an "unbind" that detaches an EPF device from
> > an EPC device?
>
> It is likely that after all of the endpoint functions are unbound, the
> controller can be stopped safely, but I'm not sure if it is desired behavior
> for endpoint framework.

I'm not asking about the patch itself.  I'm asking about the commit
log because "an EP function shouldn't stop EP controller" doesn't
quite make sense in English.

I suspect it should say something like "unbinding one endpoint
function of a multi-function device from the endpoint controller
should not stop the controller."

But I don't know enough about EPF/EPC binding to know whether that
makes sense either.

> Kishon, could you please comment?
> 
> > > Fixes: 349e7a85b25f ("PCI: endpoint: functions: Add an EP function to test PCI")
> > > Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> > > ---
> > >  drivers/pci/endpoint/functions/pci-epf-test.c | 1 -
> > >  1 file changed, 1 deletion(-)
> > >
> > > diff --git a/drivers/pci/endpoint/functions/pci-epf-test.c b/drivers/pci/endpoint/functions/pci-epf-test.c
> > > index 5b833f00e980..a5ed779b0a51 100644
> > > --- a/drivers/pci/endpoint/functions/pci-epf-test.c
> > > +++ b/drivers/pci/endpoint/functions/pci-epf-test.c
> > > @@ -627,7 +627,6 @@ static void pci_epf_test_unbind(struct pci_epf *epf)
> > >
> > >       cancel_delayed_work(&epf_test->cmd_handler);
> > >       pci_epf_test_clean_dma_chan(epf_test);
> > > -     pci_epc_stop(epc);
> > >       for (bar = 0; bar < PCI_STD_NUM_BARS; bar++) {
> > >               epf_bar = &epf->bar[bar];
> > >
> > > --
> > > 2.17.1
> > >
> 
> Thanks,
> Shunsuke