[PATCH 6/8] drm/panthor: Introduce huge tmpfs mount point option

["Loïc Molinari" <loic.molinari@collabora.com>]

Introduce the 'panthor.transparent_hugepage' boolean module parameter
(false by default). When the parameter is set to true, a new tmpfs
mount point is created and mounted using the 'huge=within_size'
option. It's then used at GEM object creation instead of the default
'shm_mnt' mount point in order to enable Transparent Hugepage (THP)
for the object (without having to rely on a system wide parameter).

Signed-off-by: Loïc Molinari <loic.molinari@collabora.com>
---
 drivers/gpu/drm/panthor/panthor_device.c |  4 ++++
 drivers/gpu/drm/panthor/panthor_device.h |  3 +++
 drivers/gpu/drm/panthor/panthor_drv.c    |  7 ++++++
 drivers/gpu/drm/panthor/panthor_drv.h    | 11 +++++++++
 drivers/gpu/drm/panthor/panthor_gem.c    | 30 +++++++++++++++++++++++-
 drivers/gpu/drm/panthor/panthor_gem.h    |  3 +++
 6 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 drivers/gpu/drm/panthor/panthor_drv.h

diff --git a/drivers/gpu/drm/panthor/panthor_device.c b/drivers/gpu/drm/panthor/panthor_device.c
index 81df49880bd8..4f254b574287 100644
--- a/drivers/gpu/drm/panthor/panthor_device.c
+++ b/drivers/gpu/drm/panthor/panthor_device.c
@@ -17,6 +17,7 @@
 #include "panthor_devfreq.h"
 #include "panthor_device.h"
 #include "panthor_fw.h"
+#include "panthor_gem.h"
 #include "panthor_gpu.h"
 #include "panthor_hw.h"
 #include "panthor_mmu.h"
@@ -98,6 +99,7 @@ void panthor_device_unplug(struct panthor_device *ptdev)
 	/* Now, try to cleanly shutdown the GPU before the device resources
 	 * get reclaimed.
 	 */
+	panthor_gem_fini(ptdev);
 	panthor_sched_unplug(ptdev);
 	panthor_fw_unplug(ptdev);
 	panthor_mmu_unplug(ptdev);
@@ -269,6 +271,8 @@ int panthor_device_init(struct panthor_device *ptdev)
 	if (ret)
 		goto err_unplug_fw;
 
+	panthor_gem_init(ptdev);
+
 	/* ~3 frames */
 	pm_runtime_set_autosuspend_delay(ptdev->base.dev, 50);
 	pm_runtime_use_autosuspend(ptdev->base.dev);
diff --git a/drivers/gpu/drm/panthor/panthor_device.h b/drivers/gpu/drm/panthor/panthor_device.h
index 4fc7cf2aeed5..54ca61567426 100644
--- a/drivers/gpu/drm/panthor/panthor_device.h
+++ b/drivers/gpu/drm/panthor/panthor_device.h
@@ -135,6 +135,9 @@ struct panthor_device {
 	/** @devfreq: Device frequency scaling management data. */
 	struct panthor_devfreq *devfreq;
 
+	/** @huge_mnt: tmpfs mount point with Transparent Hugepage enabled. */
+	struct vfsmount *huge_mnt;
+
 	/** @unplug: Device unplug related fields. */
 	struct {
 		/** @lock: Lock used to serialize unplug operations. */
diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index fdbe89ef7f43..a2be3b904ca2 100644
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1556,6 +1556,7 @@ static const struct file_operations panthor_drm_driver_fops = {
 	.read = drm_read,
 	.llseek = noop_llseek,
 	.mmap = panthor_mmap,
+	.get_unmapped_area = drm_gem_get_unmapped_area,
 	.show_fdinfo = drm_show_fdinfo,
 	.fop_flags = FOP_UNSIGNED_OFFSET,
 };
@@ -1623,6 +1624,12 @@ static const struct drm_driver panthor_drm_driver = {
 #endif
 };
 
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+bool panthor_transparent_hugepage;
+module_param_named(transparent_hugepage, panthor_transparent_hugepage, bool, 0400);
+MODULE_PARM_DESC(transparent_hugepage, "Use a dedicated tmpfs mount point with Transparent Hugepage enabled (false = default)");
+#endif
+
 static int panthor_probe(struct platform_device *pdev)
 {
 	struct panthor_device *ptdev;
diff --git a/drivers/gpu/drm/panthor/panthor_drv.h b/drivers/gpu/drm/panthor/panthor_drv.h
new file mode 100644
index 000000000000..27fe9b6f77bd
--- /dev/null
+++ b/drivers/gpu/drm/panthor/panthor_drv.h
@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: GPL-2.0 or MIT
+/* Copyright 2025 Amazon.com, Inc. or its affiliates */
+
+#ifndef __PANTHOR_DRV_H__
+#define __PANTHOR_DRV_H__
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+extern bool panthor_transparent_hugepage;
+#endif
+
+#endif
diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c
index 156c7a0b62a2..16916e0b6d89 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.c
+++ b/drivers/gpu/drm/panthor/panthor_gem.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0 or MIT
 /* Copyright 2019 Linaro, Ltd, Rob Herring <robh@kernel.org> */
 /* Copyright 2023 Collabora ltd. */
+/* Copyright 2025 Amazon.com, Inc. or its affiliates */
 
 #include <linux/cleanup.h>
 #include <linux/dma-buf.h>
@@ -11,10 +12,35 @@
 #include <drm/panthor_drm.h>
 
 #include "panthor_device.h"
+#include "panthor_drv.h"
 #include "panthor_fw.h"
 #include "panthor_gem.h"
 #include "panthor_mmu.h"
 
+void panthor_gem_init(struct panthor_device *ptdev)
+{
+	struct vfsmount *huge_mnt;
+
+	if (!panthor_transparent_hugepage)
+		return;
+
+	huge_mnt = drm_gem_shmem_huge_mnt_create("within_size");
+	if (IS_ERR(huge_mnt)) {
+		drm_warn(&ptdev->base, "Can't use Transparent Hugepage (%ld)\n",
+			 PTR_ERR(huge_mnt));
+		return;
+	}
+
+	ptdev->huge_mnt = huge_mnt;
+
+	drm_info(&ptdev->base, "Using Transparent Hugepage\n");
+}
+
+void panthor_gem_fini(struct panthor_device *ptdev)
+{
+	drm_gem_shmem_huge_mnt_free(ptdev->huge_mnt);
+}
+
 #ifdef CONFIG_DEBUG_FS
 static void panthor_gem_debugfs_bo_init(struct panthor_gem_object *bo)
 {
@@ -270,10 +296,12 @@ panthor_gem_create_with_handle(struct drm_file *file,
 			       u64 *size, u32 flags, u32 *handle)
 {
 	int ret;
+	struct panthor_device *ptdev =
+		container_of(ddev, struct panthor_device, base);
 	struct drm_gem_shmem_object *shmem;
 	struct panthor_gem_object *bo;
 
-	shmem = drm_gem_shmem_create(ddev, *size);
+	shmem = drm_gem_shmem_create_with_mnt(ddev, *size, ptdev->huge_mnt);
 	if (IS_ERR(shmem))
 		return PTR_ERR(shmem);
 
diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h
index 80c6e24112d0..6804b3912cc2 100644
--- a/drivers/gpu/drm/panthor/panthor_gem.h
+++ b/drivers/gpu/drm/panthor/panthor_gem.h
@@ -136,6 +136,9 @@ struct panthor_gem_object *to_panthor_bo(struct drm_gem_object *obj)
 	return container_of(to_drm_gem_shmem_obj(obj), struct panthor_gem_object, base);
 }
 
+void panthor_gem_init(struct panthor_device *ptdev);
+void panthor_gem_fini(struct panthor_device *ptdev);
+
 struct drm_gem_object *panthor_gem_create_object(struct drm_device *ddev, size_t size);
 
 int
-- 
2.47.3