[PATCH] drm/xe/: Mutual Exclusivity b/w Multi CCS Mode & SRIOV VF Provisioning

[Nareshkumar Gollakoti <naresh.kumar.g@intel.com>]

Due to SLA agreement between PF and VFs, multi CCS mode can't
be enabled when VFs are already enabled.
Similarly, enabling VFs is disabled when multi ccs mode enabled.

v2:function xe_device_is_vf_enabled has been refactored to
xe_sriov_pf_has_vfs_enabled and moved to xe_sriov_pf_helper.h.
The code now distinctly checks for SR-IOV VF mode and
SR-IOV PF with VFs enabled.
Log messages have been updated to explicitly state the current mode.
The function xe_multi_ccs_mode_enabled is moved to xe_device.h

Signed-off-by: Nareshkumar Gollakoti <naresh.kumar.g@intel.com>
---
 drivers/gpu/drm/xe/xe_device.h           |  8 ++++++++
 drivers/gpu/drm/xe/xe_gt_ccs_mode.c      | 14 +++++++++++---
 drivers/gpu/drm/xe/xe_pci_sriov.c        |  6 ++++++
 drivers/gpu/drm/xe/xe_sriov_pf_helpers.h | 12 ++++++++++++
 4 files changed, 37 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_device.h b/drivers/gpu/drm/xe/xe_device.h
index 32cc6323b7f6..986f9cabb897 100644
--- a/drivers/gpu/drm/xe/xe_device.h
+++ b/drivers/gpu/drm/xe/xe_device.h
@@ -172,6 +172,14 @@ static inline bool xe_device_has_lmtt(struct xe_device *xe)
 	return IS_DGFX(xe);
 }
 
+static inline bool xe_multi_ccs_mode_enabled(struct xe_device *xe)
+{
+	/* Multi CCS mode supported exclusively on GT0 */
+	struct xe_gt *gt = xe_device_get_gt(xe, 0);
+
+	return gt->ccs_mode > 1;
+}
+
 u32 xe_device_ccs_bytes(struct xe_device *xe, u64 size);
 
 void xe_device_snapshot_print(struct xe_device *xe, struct drm_printer *p);
diff --git a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
index 50fffc9ebf62..584f3245fc7d 100644
--- a/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
+++ b/drivers/gpu/drm/xe/xe_gt_ccs_mode.c
@@ -13,6 +13,7 @@
 #include "xe_gt_sysfs.h"
 #include "xe_mmio.h"
 #include "xe_sriov.h"
+#include "xe_sriov_pf_helpers.h"
 
 static void __xe_gt_apply_ccs_mode(struct xe_gt *gt, u32 num_engines)
 {
@@ -117,9 +118,16 @@ ccs_mode_store(struct device *kdev, struct device_attribute *attr,
 	u32 num_engines, num_slices;
 	int ret;
 
-	if (IS_SRIOV(xe)) {
-		xe_gt_dbg(gt, "Can't change compute mode when running as %s\n",
-			  xe_sriov_mode_to_string(xe_device_sriov_mode(xe)));
+	/*
+	 * Check if the device is:
+	 * 1. Operating as an SR-IOV Virtual Function (VF), or
+	 * 2. An SR-IOV Physical Function (PF) with one or more VFs enabled.
+	 * Enabling multi CCS mode is not permitted in either scenario.
+	 */
+	if (IS_SRIOV_VF(xe) || xe_sriov_pf_has_vfs_enabled(xe)) {
+		const char *mode_str = !strcmp(xe_sriov_mode_to_string(xe_device_sriov_mode(xe)),
+					"SR-IOV VF") ? "SR-IOV VF" : "SR-IOV PF with VFs Enabled";
+		xe_gt_dbg(gt, "Can't change compute mode when running as %s\n", mode_str);
 		return -EOPNOTSUPP;
 	}
 
diff --git a/drivers/gpu/drm/xe/xe_pci_sriov.c b/drivers/gpu/drm/xe/xe_pci_sriov.c
index af05db07162e..71c1d998ba82 100644
--- a/drivers/gpu/drm/xe/xe_pci_sriov.c
+++ b/drivers/gpu/drm/xe/xe_pci_sriov.c
@@ -155,6 +155,12 @@ static int pf_enable_vfs(struct xe_device *xe, int num_vfs)
 	xe_assert(xe, num_vfs <= total_vfs);
 	xe_sriov_dbg(xe, "enabling %u VF%s\n", num_vfs, str_plural(num_vfs));
 
+	if (xe_multi_ccs_mode_enabled(xe)) {
+		xe_sriov_info(xe, "Disable multi-ccs mode before enabling VF's\n");
+
+		return -ECANCELED;
+	}
+
 	err = xe_sriov_pf_wait_ready(xe);
 	if (err)
 		goto out;
diff --git a/drivers/gpu/drm/xe/xe_sriov_pf_helpers.h b/drivers/gpu/drm/xe/xe_sriov_pf_helpers.h
index dd1df950b021..35aff4fab56b 100644
--- a/drivers/gpu/drm/xe/xe_sriov_pf_helpers.h
+++ b/drivers/gpu/drm/xe/xe_sriov_pf_helpers.h
@@ -43,4 +43,16 @@ static inline struct mutex *xe_sriov_pf_master_mutex(struct xe_device *xe)
 	return &xe->sriov.pf.master_lock;
 }
 
+/**
+ * xe_sriov_pf_has_vfs_enabled() - Determines if the PF has any VFs enabled
+ *
+ * Return: true if one or more VFs are enabled on the PF, false otherwise.
+ */
+static inline bool xe_sriov_pf_has_vfs_enabled(const struct xe_device *xe)
+{
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+
+	return pci_num_vf(pdev) > 0;
+}
+
 #endif
-- 
2.43.0