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From: Bjorn Helgaas <helgaas@kernel.org>
To: "Marek Behún" <kabel@kernel.org>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Bjorn Helgaas <bhelgaas@google.com>,
	linux-pci@vger.kernel.org, pali@kernel.org
Subject: Re: [PATCH 09/13] PCI: aardvark: Implement re-issuing config requests on CRS response
Date: Thu, 7 Oct 2021 14:25:53 -0500	[thread overview]
Message-ID: <20211007192553.GA1259781@bhelgaas> (raw)
In-Reply-To: <20211007143625.6ad647c3@thinkpad>

On Thu, Oct 07, 2021 at 02:36:25PM +0200, Marek Behún wrote:
> On Thu, 7 Oct 2021 12:51:57 +0100
> Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> wrote:
> 
> > On Wed, Oct 06, 2021 at 03:13:05PM -0500, Bjorn Helgaas wrote:
> > 
> > [...]
> > 
> > > > We need a way for those PCI controllers to communicate to SW that
> > > > they actually received a CRS completion (and that they don't retry
> > > > in HW).  
> > > 
> > > AFAICT this would be controller-dependent.  I think some controllers
> > > have registers that control the number of retries, but of course
> > > that's completely controller-dependent, too.
> > >   
> > > > By implementing the logic in the aardvark controller that platform
> > > > information is there so to the best of my knowledge this patch
> > > > is sound.
> > > > 
> > > > I assume that the HW retry is in the specs because there is no
> > > > architected way if CRS Software Visibility is not enabled/present to
> > > > report CRS completion in an architected PCI manner but I just
> > > > don't know the entire background behind this.  
> > > 
> > > I assume an error bit would be set in the Status or Secondary Status
> > > register when a PCIe transaction fails.  I'm not sure anybody *looks*
> > > at those, though.
> > > 
> > > This still looks like a PCI controller band-aid for a device or driver
> > > problem that will likely still exist on other platforms.  
> > 
> > Yes that's true. I believe we can merge this patch (?) but it would
> > also be good if Pali/Marek have time to test on other HW and
> > maybe generalize the concept.
> 
> We are willing to try to implement a generic API if you propose should
> such API look (at least some hints).

That's the whole point -- CRS SV *is* the generic way for controllers
to report CRS completions to software.  If the controller doesn't
support CRS SV, I don't think a generic API is possible.

Or maybe I don't understand the sort of generic API you have in mind.
What sort of information do you envision the API might provide?

Bjorn

  reply	other threads:[~2021-10-07 19:25 UTC|newest]

Thread overview: 47+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-01 19:58 [PATCH 00/13] PCI: aardvark controller fixes Marek Behún
2021-10-01 19:58 ` [PATCH 01/13] PCI: Add PCI_EXP_DEVCTL_PAYLOAD_* macros Marek Behún
2021-10-02 16:05   ` Bjorn Helgaas
2021-10-04  8:43   ` Lorenzo Pieralisi
2021-10-04  9:32     ` Marek Behún
2021-10-04  9:35       ` Lorenzo Pieralisi
2021-10-01 19:58 ` [PATCH 02/13] PCI: aardvark: Fix PCIe Max Payload Size setting Marek Behún
2021-10-03 17:44   ` Marek Behún
2021-10-01 19:58 ` [PATCH 03/13] PCI: aardvark: Don't spam about PIO Response Status Marek Behún
2021-10-01 19:58 ` [PATCH 04/13] PCI: aardvark: Fix preserving PCI_EXP_RTCTL_CRSSVE flag on emulated bridge Marek Behún
2021-10-01 19:58 ` [PATCH 05/13] PCI: aardvark: Fix configuring Reference clock Marek Behún
2021-10-01 19:58 ` [PATCH 06/13] PCI: aardvark: Do not clear status bits of masked interrupts Marek Behún
2021-10-04 14:06   ` Lorenzo Pieralisi
2021-10-04 15:18     ` Marek Behún
2021-10-04 15:31     ` Marc Zyngier
2021-10-05 12:13       ` Marek Behún
2021-10-05 12:42         ` Marc Zyngier
2021-10-05 13:15           ` Pali Rohár
2021-10-05 15:42             ` Marc Zyngier
2021-10-05 18:48               ` Pali Rohár
2021-10-05 16:04             ` Lorenzo Pieralisi
2021-10-01 19:58 ` [PATCH 07/13] PCI: aardvark: Do not unmask unused interrupts Marek Behún
2021-10-01 19:58 ` [PATCH 08/13] PCI: aardvark: Deduplicate code in advk_pcie_rd_conf() Marek Behún
2021-10-01 19:58 ` [PATCH 09/13] PCI: aardvark: Implement re-issuing config requests on CRS response Marek Behún
2021-10-02 16:35   ` Bjorn Helgaas
2021-10-04  7:21     ` Marek Behún
2021-10-04  8:53       ` Lorenzo Pieralisi
2021-10-04 10:19         ` Marek Behún
2021-10-05 19:28           ` Bjorn Helgaas
2021-10-05 22:45             ` Marek Behún
2021-10-11 18:15               ` Usage of PCBIOS_* macros (Was: Re: [PATCH 09/13] PCI: aardvark: Implement re-issuing config requests on CRS response) Pali Rohár
2021-10-11 20:58                 ` Bjorn Helgaas
2021-10-06 16:29             ` [PATCH 09/13] PCI: aardvark: Implement re-issuing config requests on CRS response Lorenzo Pieralisi
2021-10-06 20:13               ` Bjorn Helgaas
2021-10-07 11:51                 ` Lorenzo Pieralisi
2021-10-07 12:36                   ` Marek Behún
2021-10-07 19:25                     ` Bjorn Helgaas [this message]
2021-10-01 19:58 ` [PATCH 10/13] PCI: aardvark: Simplify initialization of rootcap on virtual bridge Marek Behún
2021-10-04  9:44   ` Lorenzo Pieralisi
2021-10-04  9:56     ` Marek Behún
2021-10-04 10:10       ` Lorenzo Pieralisi
2021-10-01 19:58 ` [PATCH 11/13] PCI: aardvark: Fix link training Marek Behún
2021-10-01 19:58 ` [PATCH 12/13] PCI: aardvark: Fix checking for link up via LTSSM state Marek Behún
2021-10-04 13:35   ` Lorenzo Pieralisi
2021-10-01 19:58 ` [PATCH 13/13] PCI: aardvark: Fix reporting Data Link Layer Link Active Marek Behún
2021-10-04  9:53 ` [PATCH 00/13] PCI: aardvark controller fixes Lorenzo Pieralisi
2021-10-04 10:40   ` Marek Behún

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