platform/x86: p2sb: Move out of X86_PLATFORM_DEVICES dependency

The P2SB library is used for various drivers, including server
platforms. That's why the dependency on X86_PLATFORM_DEVICES
seems superfluous.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20220718145328.14374-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Hans de Goede <hdegoede@redhat.com>

1 files changed, 133 insertions, 0 deletions

diff --git a/drivers/platform/x86/p2sb.c b/drivers/platform/x86/p2sb.c
new file mode 100644
index 000000000000..fb2e141f3eb8
--- /dev/null
+++ b/drivers/platform/x86/p2sb.c
@@ -0,0 +1,133 @@
+// 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)
+
+static const struct x86_cpu_id p2sb_cpu_ids[] = {
+	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT,	PCI_DEVFN(13, 0)),
+	X86_MATCH_INTEL_FAM6_MODEL(ATOM_GOLDMONT_D,	PCI_DEVFN(31, 1)),
+	X86_MATCH_INTEL_FAM6_MODEL(ATOM_SILVERMONT_D,	PCI_DEVFN(31, 1)),
+	X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE,		PCI_DEVFN(31, 1)),
+	X86_MATCH_INTEL_FAM6_MODEL(KABYLAKE_L,		PCI_DEVFN(31, 1)),
+	X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE,		PCI_DEVFN(31, 1)),
+	X86_MATCH_INTEL_FAM6_MODEL(SKYLAKE_L,		PCI_DEVFN(31, 1)),
+	{}
+};
+
+static int p2sb_get_devfn(unsigned int *devfn)
+{
+	const struct x86_cpu_id *id;
+
+	id = x86_match_cpu(p2sb_cpu_ids);
+	if (!id)
+		return -ENODEV;
+
+	*devfn = (unsigned int)id->driver_data;
+	return 0;
+}
+
+static int p2sb_read_bar0(struct pci_dev *pdev, struct resource *mem)
+{
+	/* Copy resource from the first BAR of the device in question */
+	*mem = pdev->resource[0];
+	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);