drm/xe: Map the entire BAR0 and hold onto the initial mapping

Both MMIO registers and GGTT for root tile will need to be used earlier
during probe. Don't rely on tile count to compute the mapping size.
Further more, there's no need to remap after figuring out the real
resource size.
Signed-off-by: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Matthew Brost <matthew.brost@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_mmio.c

@@ -300,7 +300,6 @@ void xe_mmio_probe_tiles(struct xe_device *xe)
 	size_t tile_mmio_size = SZ_16M, tile_mmio_ext_size = xe->info.tile_mmio_ext_size;
 	u8 id, tile_count = xe->info.tile_count;
 	struct xe_gt *gt = xe_root_mmio_gt(xe);
-	const int mmio_bar = 0;
 	struct xe_tile *tile;
 	void *regs;
 	u32 mtcfg;
@@ -314,9 +313,6 @@ void xe_mmio_probe_tiles(struct xe_device *xe)
 		if (tile_count < xe->info.tile_count) {
 			drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
 					xe->info.tile_count, tile_count);
-			pci_iounmap(to_pci_dev(xe->drm.dev), xe->mmio.regs);
-			xe->mmio.size = (tile_mmio_size + tile_mmio_ext_size) * tile_count;
-			xe->mmio.regs = pci_iomap(to_pci_dev(xe->drm.dev), mmio_bar, xe->mmio.size);
 			xe->info.tile_count = tile_count;
 
 			/*
@@ -381,17 +377,17 @@ static int xe_verify_lmem_ready(struct xe_device *xe)
 int xe_mmio_init(struct xe_device *xe)
 {
 	struct xe_tile *root_tile = xe_device_get_root_tile(xe);
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
 	const int mmio_bar = 0;
 	int err;
 
 	/*
-	 * Map the maximum expected BAR size, which will get remapped later
-	 * if we determine that we're running on a reduced-tile system.
+	 * Map the entire BAR.
 	 * The first 16MB of the BAR, belong to the root tile, and include:
 	 * registers (0-4MB), reserved space (4MB-8MB) and GGTT (8MB-16MB).
 	 */
-	xe->mmio.size = (SZ_16M + xe->info.tile_mmio_ext_size) * xe->info.tile_count;
-	xe->mmio.regs = pci_iomap(to_pci_dev(xe->drm.dev), mmio_bar, xe->mmio.size);
+	xe->mmio.size = pci_resource_len(pdev, mmio_bar);
+	xe->mmio.regs = pci_iomap(pdev, mmio_bar, 0);
 	if (xe->mmio.regs == NULL) {
 		drm_err(&xe->drm, "failed to map registers\n");
 		return -EIO;