ecrc.c

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/*
 *    Enables/disables PCIe ECRC checking.
 *
 *    (C) Copyright 2009 Hewlett-Packard Development Company, L.P.
 *    Andrew Patterson <[email protected]>
 *
 *    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 for performance */
#define ECRC_POLICY_ON      2       /* ECRC on for data integrity */

static int ecrc_policy = ECRC_POLICY_DEFAULT;

static const char *ecrc_policy_str[] = {
    [ECRC_POLICY_DEFAULT] = "bios",
    [ECRC_POLICY_OFF] = "off",
    [ECRC_POLICY_ON] = "on"
};

static int enable_ecrc_checking(struct pci_dev *dev)
{
    int pos;
    u32 reg32;

    if (!pci_is_pcie(dev))
        return -ENODEV;

    pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
    if (!pos)
        return -ENODEV;

    pci_read_config_dword(dev, pos + PCI_ERR_CAP, &reg32);
    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;
}

static int disable_ecrc_checking(struct pci_dev *dev)
{
    int pos;
    u32 reg32;

    if (!pci_is_pcie(dev))
        return -ENODEV;

    pos = pci_find_ext_capability(dev, PCI_EXT_CAP_ID_ERR);
    if (!pos)
        return -ENODEV;

    pci_read_config_dword(dev, pos + PCI_ERR_CAP, &reg32);
    reg32 &= ~(PCI_ERR_CAP_ECRC_GENE | PCI_ERR_CAP_ECRC_CHKE);
    pci_write_config_dword(dev, pos + PCI_ERR_CAP, reg32);

    return 0;
}

void pcie_set_ecrc_checking(struct pci_dev *dev)
{
    switch (ecrc_policy) {
    case ECRC_POLICY_DEFAULT:
        return;
    case ECRC_POLICY_OFF:
        disable_ecrc_checking(dev);
        break;
    case ECRC_POLICY_ON:
        enable_ecrc_checking(dev);
        break;
    default:
        return;
    }
}

void 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;

    ecrc_policy = i;
}