drm/xe: Add proper detection of the SR-IOV PF mode

SR-IOV PF mode detection is based on PCI capability as reported by
the PCI dev_is_pf() function and additionally on 'max_vfs' module
parameter which could be also used to disable PF capability even
if SR-IOV PF capability is reported by the hardware.

Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240404154431.583-3-michal.wajdeczko@intel.com

Author: mwajdecz

drivers/gpu/drm/xe/Makefile

@@ -159,7 +159,8 @@ xe-$(CONFIG_PCI_IOV) += \
 	xe_gt_sriov_pf_control.o \
 	xe_lmtt.o \
 	xe_lmtt_2l.o \
-	xe_lmtt_ml.o
+	xe_lmtt_ml.o \
+	xe_sriov_pf.o
 
 # include helpers for tests even when XE is built-in
 ifdef CONFIG_DRM_XE_KUNIT_TEST

drivers/gpu/drm/xe/xe_device_types.h

@@ -321,6 +321,10 @@ struct xe_device {
 	struct {
 		/** @sriov.__mode: SR-IOV mode (Don't access directly!) */
 		enum xe_sriov_mode __mode;
+
+		/** @sriov.pf: PF specific data */
+		struct xe_device_pf pf;
+
 		/** @sriov.wq: workqueue used by the virtualization workers */
 		struct workqueue_struct *wq;
 	} sriov;

drivers/gpu/drm/xe/xe_sriov.c

@@ -11,6 +11,7 @@
 #include "xe_device.h"
 #include "xe_mmio.h"
 #include "xe_sriov.h"
+#include "xe_sriov_pf.h"
 
 /**
  * xe_sriov_mode_to_string - Convert enum value to string.
@@ -58,6 +59,8 @@ void xe_sriov_probe_early(struct xe_device *xe)
 	if (has_sriov) {
 		if (test_is_vf(xe))
 			mode = XE_SRIOV_MODE_VF;
+		else if (xe_sriov_pf_readiness(xe))
+			mode = XE_SRIOV_MODE_PF;
 	}
 
 	xe_assert(xe, !xe->sriov.__mode);

drivers/gpu/drm/xe/xe_sriov_pf.c

@@ -0,0 +1,89 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2023-2024 Intel Corporation
+ */
+
+#include "xe_assert.h"
+#include "xe_device.h"
+#include "xe_module.h"
+#include "xe_sriov.h"
+#include "xe_sriov_pf.h"
+#include "xe_sriov_printk.h"
+
+static unsigned int wanted_max_vfs(struct xe_device *xe)
+{
+	return xe_modparam.max_vfs;
+}
+
+static int pf_reduce_totalvfs(struct xe_device *xe, int limit)
+{
+	struct device *dev = xe->drm.dev;
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int err;
+
+	err = pci_sriov_set_totalvfs(pdev, limit);
+	if (err)
+		xe_sriov_notice(xe, "Failed to set number of VFs to %d (%pe)\n",
+				limit, ERR_PTR(err));
+	return err;
+}
+
+static bool pf_continue_as_native(struct xe_device *xe, const char *why)
+{
+	xe_sriov_dbg(xe, "%s, continuing as native\n", why);
+	pf_reduce_totalvfs(xe, 0);
+	return false;
+}
+
+/**
+ * xe_sriov_pf_readiness - Check if PF functionality can be enabled.
+ * @xe: the &xe_device to check
+ *
+ * This function is called as part of the SR-IOV probe to validate if all
+ * PF prerequisites are satisfied and we can continue with enabling PF mode.
+ *
+ * Return: true if the PF mode can be turned on.
+ */
+bool xe_sriov_pf_readiness(struct xe_device *xe)
+{
+	struct device *dev = xe->drm.dev;
+	struct pci_dev *pdev = to_pci_dev(dev);
+	int totalvfs = pci_sriov_get_totalvfs(pdev);
+	int newlimit = min_t(u16, wanted_max_vfs(xe), totalvfs);
+
+	xe_assert(xe, totalvfs <= U16_MAX);
+
+	if (!dev_is_pf(dev))
+		return false;
+
+	if (!xe_device_uc_enabled(xe))
+		return pf_continue_as_native(xe, "Guc submission disabled");
+
+	if (!newlimit)
+		return pf_continue_as_native(xe, "all VFs disabled");
+
+	pf_reduce_totalvfs(xe, newlimit);
+
+	xe->sriov.pf.device_total_vfs = totalvfs;
+	xe->sriov.pf.driver_max_vfs = newlimit;
+
+	return true;
+}
+
+/**
+ * xe_sriov_pf_print_vfs_summary - Print SR-IOV PF information.
+ * @xe: the &xe_device to print info from
+ * @p: the &drm_printer
+ *
+ * Print SR-IOV PF related information into provided DRM printer.
+ */
+void xe_sriov_pf_print_vfs_summary(struct xe_device *xe, struct drm_printer *p)
+{
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+
+	xe_assert(xe, IS_SRIOV_PF(xe));
+
+	drm_printf(p, "total: %u\n", xe->sriov.pf.device_total_vfs);
+	drm_printf(p, "supported: %u\n", xe->sriov.pf.driver_max_vfs);
+	drm_printf(p, "enabled: %u\n", pci_num_vf(pdev));
+}

drivers/gpu/drm/xe/xe_sriov_pf.h

@@ -0,0 +1,24 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * Copyright © 2023-2024 Intel Corporation
+ */
+
+#ifndef _XE_SRIOV_PF_H_
+#define _XE_SRIOV_PF_H_
+
+#include <linux/types.h>
+
+struct drm_printer;
+struct xe_device;
+
+#ifdef CONFIG_PCI_IOV
+bool xe_sriov_pf_readiness(struct xe_device *xe);
+void xe_sriov_pf_print_vfs_summary(struct xe_device *xe, struct drm_printer *p);
+#else
+static inline bool xe_sriov_pf_readiness(struct xe_device *xe)
+{
+	return false;
+}
+#endif
+
+#endif

drivers/gpu/drm/xe/xe_sriov_types.h

@@ -7,6 +7,7 @@
 #define _XE_SRIOV_TYPES_H_
 
 #include <linux/build_bug.h>
+#include <linux/types.h>
 
 /**
  * VFID - Virtual Function Identifier
@@ -37,4 +38,18 @@ enum xe_sriov_mode {
 };
 static_assert(XE_SRIOV_MODE_NONE);
 
+/**
+ * struct xe_device_pf - Xe PF related data
+ *
+ * The data in this structure is valid only if driver is running in the
+ * @XE_SRIOV_MODE_PF mode.
+ */
+struct xe_device_pf {
+	/** @device_total_vfs: Maximum number of VFs supported by the device. */
+	u16 device_total_vfs;
+
+	/** @driver_max_vfs: Maximum number of VFs supported by the driver. */
+	u16 driver_max_vfs;
+};
+
 #endif