From: Bjorn Helgaas <helgaas@kernel.org>
To: Govinda Tatti <Govinda.Tatti@Oracle.COM>
Cc: jgross@suse.com, Sinan Kaya <okaya@codeaurora.org>,
Srikanth Jampala <Jampala.Srikanth@cavium.com>,
Herbert Xu <herbert@gondor.apana.org.au>,
Satanand Burla <satananda.burla@caviumnetworks.com>,
linux-pci@vger.kernel.org,
Felix Manlunas <felix.manlunas@caviumnetworks.com>,
linux-kernel@vger.kernel.org,
Derek Chickles <derek.chickles@caviumnetworks.com>,
Christoph Hellwig <hch@infradead.org>,
JBeulich@suse.com, Russell Currey <ruscur@russell.cc>,
bhelgaas@google.com, xen-devel@lists.xenproject.org,
boris.ostrovsky@Oracle.COM,
Raghu Vatsavayi <raghu.vatsavayi@caviumnetworks.com>,
roger.pau@citrix.com
Subject: Re: [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr() interface
Date: Fri, 15 Dec 2017 12:18:02 -0600 [thread overview]
Message-ID: <20171215181801.GU30595__18567.6706642427$1513361958$gmane$org@bhelgaas-glaptop.roam.corp.google.com> (raw)
In-Reply-To: <fea075cf-fe6f-0d0b-11e4-4279fbfc280a@Oracle.COM>
[+cc Russell, Sinan, Herbert, Srikanth, Derek, Satanand, Felix, Raghu]
On Fri, Dec 15, 2017 at 09:48:02AM -0600, Govinda Tatti wrote:
> On 12/13/2017 3:24 PM, Bjorn Helgaas wrote:
> >On Wed, Dec 13, 2017 at 02:46:57PM -0600, Govinda Tatti wrote:
> >>>>>>-static bool pcie_has_flr(struct pci_dev *dev)
> >>>>>>+bool pcie_has_flr(struct pci_dev *dev)
> >>>>>> {
> >>>>>> u32 cap;
> >>>>>>@@ -3882,6 +3882,7 @@ static bool pcie_has_flr(struct pci_dev *dev)
> >>>>>> pcie_capability_read_dword(dev, PCI_EXP_DEVCAP, &cap);
> >>>>>> return cap & PCI_EXP_DEVCAP_FLR;
> >>>>>> }
> >>>>>>+EXPORT_SYMBOL_GPL(pcie_has_flr);
> >>>>>I'd rather change pcie_flr() so you could *always* call it, and
> >>>>>it would return 0, -ENOTTY, or whatever, based on whether FLR
> >>>>>is supported. Is that feasible?
> >>>>Sure, I will add pcie_has_flr() logic inside pcie_flr() and
> >>>>return appropriate values as suggested by you. Do we still want
> >>>>to retain pcie_has_flr() and its usage inside pci.c?.Otherwise,
> >>>>I will remove it and do required cleanup.
> >>>If you can restructure the code and remove pcie_has_flr() while
> >>>retaining the existing behavior of its callers, that would be
> >>>great.
> >>I checked the current usage of pcie_has_flr() and pcie_flr(). I
> >>have a couple of questions or need some clarification.
> >>
> >>1. pcie_has_flr() usage inside pci_probe_reset_function().
> >>
> >> This function is only calling pcie_has_flr() but not pcie_flr().
> >> Rest of the code is trying to do specific type of reset except
> >> pcie_flr().
> >>
> >> rc = pci_dev_specific_reset(dev, 1);
> >> if (rc != -ENOTTY)
> >> return rc;
> >> if (pcie_has_flr(dev))
> >> return 0;
> >> rc = pci_af_flr(dev, 1);
> >> if (rc != -ENOTTY)
> >> return rc;
> >>
> >> In other-words, I can remove usage of pcie_has_flr() in all
> >> other places in pci.c except in above function.
> >I think we should keep the EXPORT_SYMBOL_GPL() part of a60a2b73ba69
> >("PCI: Export pcie_flr()"), but revert the restructuring part.
> >
> >Prior to a60a2b73ba69, we had
> >
> > int pcie_flr(struct pci_dev *dev, int probe);
> >
> >like all the other reset methods. AFAICT, the addition of
> >pcie_has_flr() was to optimize the path slightly because when
> >drivers call pcie_flr(), they should already know that their
> >hardware supports FLR. But I don't think that optimization is
> >worth the extra code complexity. If we do need to optimize it, we
> >can check this in the core during enumeration and set
> >PCI_DEV_FLAGS_NO_FLR_RESET accordingly.
> Not all code paths are aware of FLR capability and also, not
> using pcie_flr(). For example,
>
> arch/powerpc/platforms/powernv/eeh-powernv.c
I assume you're referring to pnv_eeh_do_flr() (which contains code similar
to pcie_flr()) and pnv_eeh_do_af_flr() (which has code similar to
pci_af_flr()). I agree that those are problematic and would ideally be
unified with the PCI core implementations.
Powerpc has quite a bit of this sort of special-case code for several
reasons, some just historical and some more concrete, so I don't know how
feasible this is.
> drivers/crypto/cavium/nitrox/nitrox_main.c
This has nitrox_reset_device(), which should definitely be replaced with a
core interface.
> drivers/net/ethernet/cavium/liquidio/octeon_mailbox.c
And this has octeon_mbox_process_cmd() which also does a home-grown
PCI_EXP_DEVCTL_BCR_FLR request and also should definitely use a core
interface.
> So, we should consider one of these options.
>
> - set PCI_DEV_FLAGS_NO_FLR_RESET if it is not supported.
> - pcie_flr() should return if it is not supported
>
> If we modify pcie_flr() to return error codes, then we need to modify
> all existing modules that are calling this function.
Yes, of course.
> Please let me know your preference, so that I can move accordingly. Thanks.
I think Christoph volunteered to do some restructuring, but I don't
know his timeframe. If you can, I would probably wait for that
because there's so much overlap here.
The other paths that use PCI_EXP_DEVCTL_BCR_FLR are definitely issues
and should be fixed, but again should wait for the revised pcie_flr()
interface. And if they're not actually required for your Xen issue,
they sound like "nice to have" cleanups that will not gate your Xen
fixes. I added this to my ever-growing list of cleanups to do.
Bjorn
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next prev parent reply other threads:[~2017-12-15 18:18 UTC|newest]
Thread overview: 40+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20171207222145.9769-1-Govinda.Tatti@Oracle.COM>
2017-12-07 22:21 ` [PATCH V3 1/2] Drivers/PCI: Export pcie_has_flr() interface Govinda Tatti
2017-12-08 20:24 ` Bjorn Helgaas
[not found] ` <20171208202424.GC12367@bhelgaas-glaptop.roam.corp.google.com>
2017-12-12 0:29 ` Govinda Tatti
[not found] ` <426eeeab-0dcd-8de3-9c5f-a166acf2c130@Oracle.COM>
2017-12-12 0:59 ` Bjorn Helgaas
[not found] ` <20171212005919.GB30595@bhelgaas-glaptop.roam.corp.google.com>
2017-12-13 20:46 ` Govinda Tatti
[not found] ` <49956aaf-5fd5-939d-5fc7-231ffdb98b70@Oracle.COM>
2017-12-13 21:24 ` Bjorn Helgaas
[not found] ` <20171213212420.GH30595@bhelgaas-glaptop.roam.corp.google.com>
2017-12-14 12:52 ` Christoph Hellwig
[not found] ` <20171214125206.GA24958@infradead.org>
2017-12-15 0:24 ` Bjorn Helgaas
2017-12-15 15:48 ` Govinda Tatti
2017-12-15 18:18 ` Bjorn Helgaas [this message]
[not found] ` <20171215181801.GU30595@bhelgaas-glaptop.roam.corp.google.com>
2017-12-15 20:01 ` Govinda Tatti
2017-12-18 3:09 ` Alexey Kardashevskiy
2017-12-18 12:26 ` Christoph Hellwig
[not found] ` <20171218122629.GA18423@infradead.org>
2017-12-18 17:22 ` Govinda Tatti
2018-09-09 18:59 ` Pasi Kärkkäinen
[not found] ` <20180909185944.GC18222@reaktio.net>
2018-09-10 2:33 ` Sinan Kaya
[not found] ` <9ffe43d2-a44b-974c-85c9-9923d71c5dba@kernel.org>
2018-09-10 9:52 ` Pasi Kärkkäinen
[not found] ` <20180910095231.GD18222@reaktio.net>
2018-09-10 17:04 ` Sinan Kaya
2017-12-12 15:07 ` Christoph Hellwig
2017-12-07 22:21 ` [PATCH V3 2/2] Xen/PCIback: Implement PCI flr/slot/bus reset with 'reset' SysFS attribute Govinda Tatti
[not found] ` <20171207222145.9769-3-Govinda.Tatti@Oracle.COM>
2017-12-08 9:34 ` Jan Beulich
2017-12-12 14:48 ` Govinda Tatti
2017-12-12 15:01 ` Jan Beulich
[not found] ` <5A2FFD690200007800196DFB@prv-mh.provo.novell.com>
2017-12-12 15:14 ` Govinda Tatti
2017-12-15 19:52 ` Govinda Tatti
[not found] ` <f19dbb09-ef22-2cf4-fb38-2a7c42b5dc48@Oracle.COM>
2017-12-18 7:36 ` Jan Beulich
[not found] ` <5A377E020200007800197FFA@prv-mh.provo.novell.com>
2017-12-18 17:32 ` Boris Ostrovsky
[not found] ` <559ffd12-b541-8a69-60bd-fbe10e3dc159@oracle.com>
2018-09-16 11:43 ` Pasi Kärkkäinen
[not found] ` <20180916114306.GF18222@reaktio.net>
2018-09-17 18:06 ` Boris Ostrovsky
[not found] ` <a726840b-8a5c-0890-73c6-3a95a7205153@oracle.com>
2018-09-18 7:15 ` Pasi Kärkkäinen
[not found] ` <20180918071519.GG18222@reaktio.net>
2018-09-18 9:32 ` George Dunlap
[not found] ` <5E7DDB68-4E68-48A5-AEEC-EE1B21A50E9E@citrix.com>
2018-09-18 18:09 ` Boris Ostrovsky
[not found] ` <352310b3-ec9b-2ceb-83f0-4550718120c3@oracle.com>
2018-09-19 9:05 ` Roger Pau Monné
[not found] ` <20180919090526.s3ahnemrt2ik2tx3@mac.bytemobile.com>
2018-10-03 15:51 ` Pasi Kärkkäinen
[not found] ` <20181003155104.GH5318@reaktio.net>
2018-10-08 14:32 ` Boris Ostrovsky
[not found] ` <f6b8e055-7afc-b4de-af88-425d799dcd28@oracle.com>
2018-10-23 18:40 ` Håkon Alstadheim
2018-10-29 15:30 ` Pasi Kärkkäinen
2018-11-14 14:24 ` [PATCH cargo-cult-version] For linux-4.19.x . " Håkon Alstadheim
2019-08-26 21:05 ` [Xen-devel] [PATCH V3 2/2] " Pasi Kärkkäinen
2017-12-12 15:01 ` Govinda Tatti
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