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

SR-IOV VF mode detection is based on testing VF capability bit on
the register that is accessible from both the PF and enabled VFs.

Bspec: 49904, 53227
Signed-off-by: Michal Wajdeczko <michal.wajdeczko@intel.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240327182740.407-4-michal.wajdeczko@intel.com

drivers/gpu/drm/xe/regs/xe_sriov_regs.h

@@ -14,4 +14,7 @@
 #define   LMEM_EN			REG_BIT(31)
 #define   LMTT_DIR_PTR			REG_GENMASK(30, 0) /* in multiples of 64KB */
 
+#define VF_CAP_REG			XE_REG(0x1901f8, XE_REG_OPTION_VF)
+#define   VF_CAP			REG_BIT(0)
+
 #endif

drivers/gpu/drm/xe/xe_sriov.c

@@ -5,7 +5,11 @@
 
 #include <drm/drm_managed.h>
 
+#include "regs/xe_sriov_regs.h"
+
 #include "xe_assert.h"
+#include "xe_device.h"
+#include "xe_mmio.h"
 #include "xe_sriov.h"
 
 /**
@@ -28,6 +32,13 @@ const char *xe_sriov_mode_to_string(enum xe_sriov_mode mode)
 	}
 }
 
+static bool test_is_vf(struct xe_device *xe)
+{
+	u32 value = xe_mmio_read32(xe_root_mmio_gt(xe), VF_CAP_REG);
+
+	return value & VF_CAP;
+}
+
 /**
  * xe_sriov_probe_early - Probe a SR-IOV mode.
  * @xe: the &xe_device to probe mode on
@@ -44,8 +55,10 @@ void xe_sriov_probe_early(struct xe_device *xe)
 	enum xe_sriov_mode mode = XE_SRIOV_MODE_NONE;
 	bool has_sriov = xe->info.has_sriov;
 
-	/* TODO: replace with proper mode detection */
-	xe_assert(xe, !has_sriov);
+	if (has_sriov) {
+		if (test_is_vf(xe))
+			mode = XE_SRIOV_MODE_VF;
+	}
 
 	xe_assert(xe, !xe->sriov.__mode);
 	xe->sriov.__mode = mode;