From: Lukas Wunner <lukas@wunner.de>
To: "Pali Rohár" <pali@kernel.org>
Cc: Naveen Naidu <naveennaidu479@gmail.com>,
bhelgaas@google.com,
linux-kernel-mentees@lists.linuxfoundation.org,
linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@linux.intel.com>,
Amey Narkhede <ameynarkhede03@gmail.com>
Subject: Re: [PATCH 16/22] PCI: pciehp: Use RESPONSE_IS_PCI_ERROR() to check read from hardware
Date: Wed, 13 Oct 2021 14:20:19 +0200 [thread overview]
Message-ID: <20211013122019.GA17324@wunner.de> (raw)
In-Reply-To: <20211012231201.xj7fvfgvpde5wwrl@pali>
On Wed, Oct 13, 2021 at 01:12:01AM +0200, Pali Rohár wrote:
> > On 11/10, Lukas Wunner wrote:
> > > On Mon, Oct 11, 2021 at 11:37:33PM +0530, Naveen Naidu wrote:
> > > > An MMIO read from a PCI device that doesn't exist or doesn't respond
> > > > causes a PCI error. There's no real data to return to satisfy the
> > > > CPU read, so most hardware fabricates ~0 data.
> > > >
> > > > Use RESPONSE_IS_PCI_ERROR() to check the response we get when we read
> > > > data from hardware.
> > >
> > > Actually what happens is that PCI read transactions *time out*,
> > > so the host controller fabricates a response.
>
> This is not fully correct. 0xffffffff is returned when some error
> happens. It does not have to be timeout error. Errors like Unsupported
> Request, Completer Abort or Configuration Request Retry Status (when
> CRSSVE bit is disabled) are also reported as 0xffffffff and they do not
> represent timeout. For example Unsupported Request is returned when you
> try to read from non-existent device behind some PCIe switch.
This particular patch concerns pciehp and in that context,
"all ones" responses are predominantly timeouts caused by
hot-removed devices.
Thanks,
Lukas
next prev parent reply other threads:[~2021-10-13 12:25 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-11 17:35 [PATCH 00/22] PCI: Unify PCI error response checking Naveen Naidu
2021-10-11 17:37 ` [PATCH 01/22] PCI: Add PCI_ERROR_RESPONSE and it's related defintions Naveen Naidu
2021-10-11 17:38 ` [PATCH 02/22] PCI: Unify PCI error response checking Naveen Naidu
2021-10-11 22:05 ` Rob Herring
2021-10-12 16:21 ` Naveen Naidu
2021-10-12 18:02 ` Rob Herring
2021-10-12 22:52 ` Pali Rohár
2021-10-13 2:43 ` Bjorn Helgaas
2021-10-13 13:06 ` Rob Herring
2021-10-13 17:16 ` Naveen Naidu
2021-10-13 17:54 ` Pali Rohár
2021-10-13 18:48 ` Bjorn Helgaas
2021-10-13 21:47 ` Rob Herring
2021-10-13 22:03 ` Pali Rohár
2021-10-13 22:12 ` Bjorn Helgaas
2021-10-11 17:45 ` [PATCH 03/22] PCI: thunder: Use SET_PCI_ERROR_RESPONSE() when device not found Naveen Naidu
2021-10-11 17:46 ` [PATCH 04/22] PCI: iproc: " Naveen Naidu
2021-10-11 17:51 ` [PATCH 05/22] PCI: mediatek: " Naveen Naidu
2021-10-11 17:52 ` [PATCH 06/22] PCI: exynos: " Naveen Naidu
2021-10-11 17:53 ` [PATCH 07/22] PCI: histb: " Naveen Naidu
2021-10-11 17:55 ` [PATCH 08/22] PCI: kirin: " Naveen Naidu
2021-10-11 17:56 ` [PATCH 09/22] PCI: aardvark: " Naveen Naidu
2021-10-11 18:08 ` Pali Rohár
2021-10-11 18:28 ` Naveen Naidu
[not found] ` <20211011182526.kboaxqofdpd2jjrl@theprophet>
2021-10-11 18:41 ` Pali Rohár
2021-10-12 15:59 ` Naveen Naidu
2021-10-13 2:13 ` Bjorn Helgaas
2021-10-13 17:59 ` Pali Rohár
2021-10-11 18:00 ` [PATCH 10/22] PCI: mvebu: " Naveen Naidu
2021-10-11 18:00 ` [PATCH 11/22] PCI: altera: " Naveen Naidu
2021-10-11 18:02 ` [PATCH 12/22] PCI: rcar: " Naveen Naidu
2021-10-11 18:02 ` [PATCH 13/22] PCI: rockchip: " Naveen Naidu
2021-10-11 18:04 ` [PATCH 14/22] PCI/ERR: Use RESPONSE_IS_PCI_ERROR() to check read from hardware Naveen Naidu
2021-10-11 18:06 ` [PATCH 15/22] PCI: vmd: " Naveen Naidu
2021-10-14 18:04 ` Jonathan Derrick
2021-10-11 18:07 ` [PATCH 16/22] PCI: pciehp: " Naveen Naidu
2021-10-11 19:47 ` Lukas Wunner
2021-10-12 16:05 ` Naveen Naidu
2021-10-12 23:12 ` Pali Rohár
2021-10-13 12:20 ` Lukas Wunner [this message]
2021-10-11 18:08 ` [PATCH 17/22] PCI/DPC: " Naveen Naidu
2021-10-11 18:10 ` [PATCH 18/22] PCI/PME: " Naveen Naidu
2021-10-11 18:11 ` [PATCH 19/22] PCI: cpqphp: " Naveen Naidu
2021-10-11 18:11 ` [PATCH 20/22] PCI: keystone: Use PCI_ERROR_RESPONSE to specify hardware error Naveen Naidu
2021-10-11 18:12 ` [PATCH 21/22] PCI: hv: Use PCI_ERROR_RESPONSE to specify hardware read error Naveen Naidu
2021-10-11 18:13 ` [PATCH 22/22] PCI: xgene: Use PCI_ERROR_RESPONSE to specify hardware error Naveen Naidu
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