1 files changed, 106 insertions, 0 deletions
diff --git a/drivers/gpu/drm/xe/xe_pci_rebar.c b/drivers/gpu/drm/xe/xe_pci_rebar.c
new file mode 100644
index 000000000000..7e2c7079b6ff
--- /dev/null
+++ b/drivers/gpu/drm/xe/xe_pci_rebar.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: MIT
+/*
+ * Copyright © 2025 Intel Corporation
+ */
+
+#include <linux/pci.h>
+#include <linux/types.h>
+
+#include "regs/xe_bars.h"
+#include "xe_device_types.h"
+#include "xe_module.h"
+#include "xe_pci_rebar.h"
+#include "xe_printk.h"
+
+static void resize_bar(struct xe_device *xe, int resno, resource_size_t size)
+{
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+	int bar_size = pci_rebar_bytes_to_size(size);
+	int ret;
+
+	ret = pci_resize_resource(pdev, resno, bar_size, 0);
+	if (ret) {
+		xe_info(xe, "Failed to resize BAR%d to %dMiB (%pe). Consider enabling 'Resizable BAR' support in your BIOS\n",
+			resno, 1 << bar_size, ERR_PTR(ret));
+		return;
+	}
+
+	xe_info(xe, "BAR%d resized to %dMiB\n", resno, 1 << bar_size);
+}
+
+/*
+ * xe_pci_rebar_resize - Resize the LMEMBAR
+ * @xe: xe device instance
+ *
+ * If vram_bar_size module param is set, attempt to set to the requested size
+ * else set to maximum possible size.
+ */
+void xe_pci_rebar_resize(struct xe_device *xe)
+{
+	int force_vram_bar_size = xe_modparam.force_vram_bar_size;
+	struct pci_dev *pdev = to_pci_dev(xe->drm.dev);
+	struct pci_bus *root = pdev->bus;
+	resource_size_t current_size;
+	resource_size_t rebar_size;
+	struct resource *root_res;
+	int max_size, i;
+	u32 pci_cmd;
+
+	/* gather some relevant info */
+	current_size = pci_resource_len(pdev, LMEM_BAR);
+
+	if (force_vram_bar_size < 0)
+		return;
+
+	/* set to a specific size? */
+	if (force_vram_bar_size) {
+		rebar_size = pci_rebar_bytes_to_size(force_vram_bar_size *
+						     (resource_size_t)SZ_1M);
+
+		if (!pci_rebar_size_supported(pdev, LMEM_BAR, rebar_size)) {
+			xe_info(xe, "Requested size %lluMiB is not supported by rebar sizes: 0x%llx. Leaving default: %lluMiB\n",
+				(u64)pci_rebar_size_to_bytes(rebar_size) >> ilog2(SZ_1M),
+				pci_rebar_get_possible_sizes(pdev, LMEM_BAR),
+				(u64)current_size >> ilog2(SZ_1M));
+			return;
+		}
+
+		rebar_size = pci_rebar_size_to_bytes(rebar_size);
+		if (rebar_size == current_size)
+			return;
+	} else {
+		max_size = pci_rebar_get_max_size(pdev, LMEM_BAR);
+		if (max_size < 0)
+			return;
+		rebar_size = pci_rebar_size_to_bytes(max_size);
+
+		/* only resize if larger than current */
+		if (rebar_size <= current_size)
+			return;
+	}
+
+	xe_info(xe, "Attempting to resize bar from %lluMiB -> %lluMiB\n",
+		(u64)current_size >> ilog2(SZ_1M), (u64)rebar_size >> ilog2(SZ_1M));
+
+	while (root->parent)
+		root = root->parent;
+
+	pci_bus_for_each_resource(root, root_res, i) {
+		if (root_res && root_res->flags & (IORESOURCE_MEM | IORESOURCE_MEM_64) &&
+		    (u64)root_res->start > 0x100000000ul)
+			break;
+	}
+
+	if (!root_res) {
+		xe_info(xe, "Can't resize VRAM BAR - platform support is missing. Consider enabling 'Resizable BAR' support in your BIOS\n");
+		return;
+	}
+
+	pci_read_config_dword(pdev, PCI_COMMAND, &pci_cmd);
+	pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd & ~PCI_COMMAND_MEMORY);
+
+	resize_bar(xe, LMEM_BAR, rebar_size);
+
+	pci_assign_unassigned_bus_resources(pdev->bus);
+	pci_write_config_dword(pdev, PCI_COMMAND, pci_cmd);
+}