drm/xe: Allow to drop vram resizing

The default behavior if the LMEMBAR doesn't match the maximum possible
size is to try to resize it. However the user might want to keep, even
for testing the behavior with small BAR, whatever size was set via
sysfs. Change the module parameter to int and check for negative value.

Cc: Michał Winiarski <michal.winiarski@intel.com>
Reviewed-by: Michał Winiarski <michal.winiarski@intel.com>
Link: https://lore.kernel.org/r/20250409-bar-resize-param-v1-1-75bf4df38aa0@intel.com
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>

Author: Lucas De Marchi

drivers/gpu/drm/xe/xe_module.c

@@ -39,8 +39,8 @@ MODULE_PARM_DESC(force_execlist, "Force Execlist submission");
 module_param_named(probe_display, xe_modparam.probe_display, bool, 0444);
 MODULE_PARM_DESC(probe_display, "Probe display HW, otherwise it's left untouched (default: true)");
 
-module_param_named(vram_bar_size, xe_modparam.force_vram_bar_size, uint, 0600);
-MODULE_PARM_DESC(vram_bar_size, "Set the vram bar size(in MiB)");
+module_param_named(vram_bar_size, xe_modparam.force_vram_bar_size, int, 0600);
+MODULE_PARM_DESC(vram_bar_size, "Set the vram bar size (in MiB) - <0=disable-resize, 0=max-needed-size[default], >0=force-size");
 
 module_param_named(guc_log_level, xe_modparam.guc_log_level, int, 0600);
 MODULE_PARM_DESC(guc_log_level, "GuC firmware logging level (0=disable, 1..5=enable with verbosity min..max)");

drivers/gpu/drm/xe/xe_vram.c

@@ -49,7 +49,7 @@ _resize_bar(struct xe_device *xe, int resno, resource_size_t size)
  */
 static void resize_vram_bar(struct xe_device *xe)
 {
-	u64 force_vram_bar_size = xe_modparam.force_vram_bar_size;
+	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;
@@ -66,6 +66,9 @@ static void resize_vram_bar(struct xe_device *xe)
 	if (!bar_size_mask)
 		return;
 
+	if (force_vram_bar_size < 0)
+		return;
+
 	/* set to a specific size? */
 	if (force_vram_bar_size) {
 		u32 bar_size_bit;