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// SPDX-License-Identifier: GPL-2.0
/*
* Primary to Sideband (P2SB) bridge access support
*
* Copyright (c) 2017, 2021-2022 Intel Corporation.
*
* Authors: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
* Jonathan Yong <jonathan.yong@intel.com>
*/
#include <linux/bits.h>
#include <linux/export.h>
#include <linux/pci.h>
#include <linux/platform_data/x86/p2sb.h>
#include <asm/cpu_device_id.h>
#include <asm/intel-family.h>
#define P2SBC 0xe0
#define P2SBC_HIDE BIT(8)
#define P2SB_DEVFN_DEFAULT PCI_DEVFN(31, 1)
static const struct x86_cpu_id p2sb_cpu_ids[] = {
X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT, PCI_DEVFN(13, 0)),
{}
};
static int p2sb_get_devfn(unsigned int *devfn)
{
unsigned int fn = P2SB_DEVFN_DEFAULT;
const struct x86_cpu_id *id;
id = x86_match_cpu(p2sb_cpu_ids);
if (id)
fn = (unsigned int)id->driver_data;
*devfn = fn;
return 0;
}
/* Copy resource from the first BAR of the device in question */
static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
{
struct resource *bar0 = &pdev->resource[0];
/* Make sure we have no dangling pointers in the output */
memset(mem, 0, sizeof(*mem));
/*
* We copy only selected fields from the original resource.
* Because a PCI device will be removed soon, we may not use
* any allocated data, hence we may not copy any pointers.
*/
mem->start = bar0->start;
mem->end = bar0->end;
mem->flags = bar0->flags;
mem->desc = bar0->desc;
return 0;
}
static int p2sb_scan_and_read(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
{
struct pci_dev *pdev;
int ret;
pdev = pci_scan_single_device(bus, devfn);
if (!pdev)
return -ENODEV;
ret = p2sb_read_bar0(pdev, mem);
pci_stop_and_remove_bus_device(pdev);
return ret;
}
/**
* p2sb_bar - Get Primary to Sideband (P2SB) bridge device BAR
* @bus: PCI bus to communicate with
* @devfn: PCI slot and function to communicate with
* @mem: memory resource to be filled in
*
* The BIOS prevents the P2SB device from being enumerated by the PCI
* subsystem, so we need to unhide and hide it back to lookup the BAR.
*
* if @bus is NULL, the bus 0 in domain 0 will be used.
* If @devfn is 0, it will be replaced by devfn of the P2SB device.
*
* Caller must provide a valid pointer to @mem.
*
* Locking is handled by pci_rescan_remove_lock mutex.
*
* Return:
* 0 on success or appropriate errno value on error.
*/
int p2sb_bar(struct pci_bus *bus, unsigned int devfn, struct resource *mem)
{
struct pci_dev *pdev_p2sb;
unsigned int devfn_p2sb;
u32 value = P2SBC_HIDE;
int ret;
/* Get devfn for P2SB device itself */
ret = p2sb_get_devfn(&devfn_p2sb);
if (ret)
return ret;
/* if @bus is NULL, use bus 0 in domain 0 */
bus = bus ?: pci_find_bus(0, 0);
/*
* Prevent concurrent PCI bus scan from seeing the P2SB device and
* removing via sysfs while it is temporarily exposed.
*/
pci_lock_rescan_remove();
/* Unhide the P2SB device, if needed */
pci_bus_read_config_dword(bus, devfn_p2sb, P2SBC, &value);
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, 0);
pdev_p2sb = pci_scan_single_device(bus, devfn_p2sb);
if (devfn)
ret = p2sb_scan_and_read(bus, devfn, mem);
else
ret = p2sb_read_bar0(pdev_p2sb, mem);
pci_stop_and_remove_bus_device(pdev_p2sb);
/* Hide the P2SB device, if it was hidden */
if (value & P2SBC_HIDE)
pci_bus_write_config_dword(bus, devfn_p2sb, P2SBC, P2SBC_HIDE);
pci_unlock_rescan_remove();
if (ret)
return ret;
if (mem->flags == 0)
return -ENODEV;
return 0;
}
EXPORT_SYMBOL_GPL(p2sb_bar);
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