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Message-Id: <1238777923.19984.110.camel@grinch>
Date: Fri, 03 Apr 2009 16:58:42 +0000
From: Andrew Patterson <andrew.patterson@...com>
To: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
jbarnes@...tuousgeek.org
Subject: Re: [PATCH] Add support for turning PCIe ECRC on or off
On Fri, 2009-04-03 at 11:08 +0900, Kenji Kaneshige wrote:
> Andrew Patterson wrote:
> > Add support for turning PCIe ECRC on or off
> >
> > Adds support for PCI Express transaction layer end-to-end CRC checking
> > (ECRC). This patch will enable/disable ECRC checking by setting/clearing
> > the ECRC Check Enable and/or ECRC Generation Enable bits for devices that
> > support ECRC.
> >
> > The ECRC setting is controlled by the "pcie_ecrc=" command-line option. If
> > this option is not set or is set to 'default", the enable and generation
> > bits are left in whatever state that firmware/BIOS sets them to. The
> > "off" setting turns them off, and the "on" option turns them on (if the
> > device supports it).
> >
> > Signed-off-by: Andrew Patterson <andrew.patterson@...com>
> > ---
> >
> > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> > index 1754fed..c346b55 100644
> > --- a/Documentation/kernel-parameters.txt
> > +++ b/Documentation/kernel-parameters.txt
> > @@ -1776,6 +1776,12 @@ and is between 256 and 4096 characters. It is defined in the file
> > force Enable ASPM even on devices that claim not to support it.
> > WARNING: Forcing ASPM on may cause system lockups.
> >
> > + pcie_ecrc= [PCI] Enable/disable PCIe ECRC (transaction layer
> > + end-to-end CRC checking).
> > + pcie_ecrc=default: Use BIOS/firmware settings.
> > + pcie_ecrc=off: Turn ECRC off
> > + pcie_ecrc=on: Turn ECRC on.
> > +
> > pcmv= [HW,PCMCIA] BadgePAD 4
> >
> > pd. [PARIDE]
> > diff --git a/drivers/pci/pcie/Kconfig b/drivers/pci/pcie/Kconfig
> > index 5a0c6ad..d90f831 100644
> > --- a/drivers/pci/pcie/Kconfig
> > +++ b/drivers/pci/pcie/Kconfig
> > @@ -46,3 +46,15 @@ config PCIEASPM_DEBUG
> > help
> > This enables PCI Express ASPM debug support. It will add per-device
> > interface to control ASPM.
> > +
> > +#
> > +# PCI Express ECRC
> > +#
> > +config PCIEECRC
> > + bool "PCI Express ECRC support"
> > + depends on PCI
> > + help
> > + Enables PCI Express ECRC (transaction layer end-to-end CRC
> > + checking)
> > +
> > + When in doubt, say N.
> > diff --git a/drivers/pci/pcie/Makefile b/drivers/pci/pcie/Makefile
> > index 11f6bb1..acef212 100644
> > --- a/drivers/pci/pcie/Makefile
> > +++ b/drivers/pci/pcie/Makefile
> > @@ -5,6 +5,9 @@
> > # Build PCI Express ASPM if needed
> > obj-$(CONFIG_PCIEASPM) += aspm.o
> >
> > +# Build PCI Express ECRC if needed
> > +obj-$(CONFIG_PCIEECRC) += ecrc.o
> > +
> > pcieportdrv-y := portdrv_core.o portdrv_pci.o portdrv_bus.o
> >
> > obj-$(CONFIG_PCIEPORTBUS) += pcieportdrv.o
> > diff --git a/drivers/pci/pcie/ecrc.c b/drivers/pci/pcie/ecrc.c
> > new file mode 100644
> > index 0000000..eeb93df
> > --- /dev/null
> > +++ b/drivers/pci/pcie/ecrc.c
> > @@ -0,0 +1,94 @@
> > +/*
> > + * Enables/disables PCIe ECRC checking.
> > + *
> > + * (C) Copyright 20009 Hewlett-Packard Development Company, L.P.
> > + * Andrew Patterson <andrew.patterson@...com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License as published by
> > + * the Free Software Foundation; version 2 of the License.
> > + *
> > + * This program is distributed in the hope that it will be useful,
> > + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> > + * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. See the GNU
> > + * General Public License for more details.
> > + *
> > + * You should have received a copy of the GNU General Public License
> > + * along with this program; if not, write to the Free Software
> > + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
> > + * 02111-1307, USA.
> > + *
> > + */
> > +
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/module.h>
> > +#include <linux/moduleparam.h>
> > +#include <linux/pci.h>
> > +#include <linux/pci_regs.h>
> > +#include <linux/errno.h>
> > +#include "../pci.h"
> > +
> > +#define ECRC_POLICY_DEFAULT 0 /* ECRC set by BIOS */
> > +#define ECRC_POLICY_OFF 1 /* ECRC off */
> > +#define ECRC_POLICY_ON 2 /* ECRC on */
> > +
> > +static int ecrc_policy = ECRC_POLICY_DEFAULT;
> > +
> > +static const char *ecrc_policy_str[] = {
> > + [ECRC_POLICY_DEFAULT] = "default",
> > + [ECRC_POLICY_OFF] = "off",
> > + [ECRC_POLICY_ON] = "on"
> > +};
> > +
> > +/**
> > + * pcie_set_ercr_checking - enable/disable PCIe ECRC checking
> > + * @dev: the PCI device
> > + *
> > + * Returns 0 on success, or negative on failure.
> > + */
> > +int pcie_set_ecrc_checking(struct pci_dev *dev)
> > +{
> > + int pos;
> > + u32 reg32;
> > +
> > + if (!dev->is_pcie)
> > + return -ENODEV;
> > +
> > + /* Use firmware/BIOS setting if default */
> > + if (ecrc_policy == ECRC_POLICY_DEFAULT)
> > + return 0;
> > +
> > + pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
> > + if (!pos)
> > + return -ENODEV;
> > +
> > + pci_read_config_dword(dev, pos + PCI_ERR_CAP, ®32);
> > + if (ecrc_policy == ECRC_POLICY_OFF) {
> > + reg32 &= ~(PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
> > + } else if (ecrc_policy == ECRC_POLICY_ON) {
> > + if (reg32 & PCI_ERR_CAP_ECRC_GENC)
> > + reg32 |= PCI_ERR_CAP_ECRC_GENE;
> > + if (reg32 & PCI_ERR_CAP_ECRC_CHKC)
> > + reg32 |= PCI_ERR_CAP_ECRC_CHKE;
> > + }
> > + pci_write_config_dword(dev, pos + PCI_ERR_CAP, reg32);
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(pcie_set_ecrc_checking);
>
> I think this EXPORT_SYMBOL_GPL() is redundant.
I'll remove this.
>
> By the way, I have the following question and comment, though I'm not
> familiar with ECRC at all.
>
> - This patch seems to change PCI Express Advanced Error capabilities
> and Control Register. Can we do it without requesting control over
> PCI Express Advanced Error reporting?
I believe so. The spec says:
The capability to generate and check ECRC is reported to software, and
the ability to do so is enabled by software (see Section 7.10.7)
and:
If a device supports ECRC generation/checking, at least one of its
Functions must support Advanced Error Reporting (see Section 6.2)
Does "supporting AER" mean that we must request software control for
before using it? I would think that the ECRC Check Capable and ECRC
Generation Capable bits are letting us know if we can use this feature.
>
> - What about implementing ECRC on/off feature as one of the feature
> of existing AER driver.
>
I originally started down this path, but came to the conclusion that AER
reporting is not required to use this feature. We have systems that
generate NMIs/MCAs for an ECRC violation even if AER is not enabled.
Andrew
> Thanks,
> Kenji Kaneshige
>
>
>
> > +
> > +static int __init pcie_ecrc_get_policy(char *str)
> > +{
> > + int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(ecrc_policy_str); i++)
> > + if (!strncmp(str, ecrc_policy_str[i],
> > + strlen(ecrc_policy_str[i])))
> > + break;
> > + if (i >= ARRAY_SIZE(ecrc_policy_str))
> > + return 0;
> > +
> > + ecrc_policy = i;
> > + return 1;
> > +}
> > +__setup("pcie_ecrc=", pcie_ecrc_get_policy);
> > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> > index e2f3dd0..e2b0ab5 100644
> > --- a/drivers/pci/probe.c
> > +++ b/drivers/pci/probe.c
> > @@ -984,6 +984,9 @@ static void pci_init_capabilities(struct pci_dev *dev)
> >
> > /* Single Root I/O Virtualization */
> > pci_iov_init(dev);
> > +
> > + /* PCIe ECRC */
> > + pcie_set_ecrc_checking(dev);
> > }
> >
> > void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index 507552d..080afd8 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -879,6 +879,15 @@ static inline int pcie_aspm_enabled(void)
> > extern int pcie_aspm_enabled(void);
> > #endif
> >
> > +#ifndef CONFIG_PCIEECRC
> > +static inline int pcie_set_ecrc_checking(struct pci_dev *dev)
> > +{
> > + return 0;
> > +}
> > +#else
> > +extern int pcie_set_ecrc_checking(struct pci_dev *dev);
> > +#endif
> > +
> > #define pci_enable_msi(pdev) pci_enable_msi_block(pdev, 1)
> >
> > #ifdef CONFIG_HT_IRQ
> >
> > --
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> > More majordomo info at http://vger.kernel.org/majordomo-info.html
> >
> >
>
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