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From: Bjorn Helgaas <helgaas@kernel.org>
To: "Pali Rohár" <pali@kernel.org>
Cc: "Lorenzo Pieralisi" <lorenzo.pieralisi@arm.com>,
	"Bjorn Helgaas" <bhelgaas@google.com>,
	"Thomas Petazzoni" <thomas.petazzoni@bootlin.com>,
	"Marek Behún" <kabel@kernel.org>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [RESEND PATCH 2/3] PCI: aardvark: Fix checking for PIO status
Date: Tue, 20 Jul 2021 13:30:42 -0500	[thread overview]
Message-ID: <20210720183042.GA108003@bjorn-Precision-5520> (raw)
In-Reply-To: <20210720181155.lhmbrcvlnkhdj32o@pali>

On Tue, Jul 20, 2021 at 08:11:55PM +0200, Pali Rohár wrote:
> On Tuesday 20 July 2021 11:34:51 Bjorn Helgaas wrote:
> > On Tue, Jul 20, 2021 at 04:49:55PM +0200, Pali Rohár wrote:

> > > So what should pci-aardvark driver in this case do? Return ~0 or re-send
> > > this config read request (and how many times)?
> > 
> > That's a good question.  I don't know what other hardware
> > implementations do, but I doubt they retry forever.  Since the spec
> > doesn't specify a number of retries, I think you can choose to do
> > none and immediately return ~0.
> 
> Ok, so I will change implementation to return ~0 without any retry. This
> is simple and easy implementation. Anyway, it would be nice to know what
> other real-hardware implementations of PCIe controllers are doing.
> 
> PCI_EXP_RTCTL_CRSSVE bit is only part of kernel emulated PCIe Bridge and
> has no real register in aardvark hw.
> 
> So for me it looks like that aardvark's pci_ops.read() should set read
> value to ~0 or 0xffff0001 based on what is stored in kernel emulated
> PCI_EXP_RTCTL_CRSSVE bit. Right?

Yes, that would be my advice.  Of course it's only if we're reading
the Vendor ID *and* PCI_EXP_RTCTL_CRSSVE is set.

  reply	other threads:[~2021-07-20 18:30 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-24 21:33 [RESEND PATCH 0/3] PCI: aardvark: PIO fixes Pali Rohár
2021-06-24 21:33 ` [RESEND PATCH 1/3] PCI: aardvark: Fix checking for PIO Non-posted Request Pali Rohár
2021-06-24 21:33 ` [RESEND PATCH 2/3] PCI: aardvark: Fix checking for PIO status Pali Rohár
2021-06-25 11:04   ` Lorenzo Pieralisi
2021-06-25 11:21     ` Pali Rohár
2021-07-19 23:12     ` Bjorn Helgaas
2021-07-20 14:49       ` Pali Rohár
2021-07-20 16:34         ` Bjorn Helgaas
2021-07-20 18:11           ` Pali Rohár
2021-07-20 18:30             ` Bjorn Helgaas [this message]
2021-07-21 21:05             ` Bjorn Helgaas
2021-06-24 21:33 ` [RESEND PATCH 3/3] PCI: aardvark: Increase polling delay to 1.5s while waiting for PIO response Pali Rohár
2021-06-25 11:44 ` [RESEND PATCH 0/3] PCI: aardvark: PIO fixes Lorenzo Pieralisi
2021-07-22 14:40 ` [PATCH v2 0/4] " Pali Rohár
2021-07-22 14:40   ` [PATCH v2 1/4] PCI: aardvark: Fix checking for PIO status Pali Rohár
2021-07-22 14:40   ` [PATCH v2 2/4] PCI: aardvark: Increase polling delay to 1.5s while waiting for PIO response Pali Rohár
2021-07-22 14:40   ` [PATCH v2 3/4] PCI: pci-bridge-emul: Add PCIe Root Capabilities Register Pali Rohár
2021-07-22 14:40   ` [PATCH v2 4/4] PCI: aardvark: Fix reporting CRS value Pali Rohár
2021-08-05  9:54   ` [PATCH v2 0/4] PCI: aardvark: PIO fixes Lorenzo Pieralisi

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