[RFC PATCH 4/4] drm/xe: Add atomic_svm_timeslice_ms debugfs entry

[Matthew Brost]

Add some informal control for atomic SVM fault GPU timeslice to be able
to play around with values and tweak performance.

Signed-off-by: Matthew Brost <matthew.brost at intel.com>
---
 drivers/gpu/drm/xe/xe_debugfs.c      | 38 ++++++++++++++++++++++++++++
 drivers/gpu/drm/xe/xe_device.c       |  1 +
 drivers/gpu/drm/xe/xe_device_types.h |  3 +++
 drivers/gpu/drm/xe/xe_svm.c          |  2 +-
 4 files changed, 43 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_debugfs.c b/drivers/gpu/drm/xe/xe_debugfs.c
index d0503959a8ed..d83cd6ed3fa8 100644
--- a/drivers/gpu/drm/xe/xe_debugfs.c
+++ b/drivers/gpu/drm/xe/xe_debugfs.c
@@ -191,6 +191,41 @@ static const struct file_operations wedged_mode_fops = {
 	.write = wedged_mode_set,
 };
 
+static ssize_t atomic_svm_timeslice_ms_show(struct file *f, char __user *ubuf,
+					    size_t size, loff_t *pos)
+{
+	struct xe_device *xe = file_inode(f)->i_private;
+	char buf[32];
+	int len = 0;
+
+	len = scnprintf(buf, sizeof(buf), "%d\n", xe->atomic_svm_timeslice_ms);
+
+	return simple_read_from_buffer(ubuf, size, pos, buf, len);
+}
+
+static ssize_t atomic_svm_timeslice_ms_set(struct file *f,
+					   const char __user *ubuf,
+					   size_t size, loff_t *pos)
+{
+	struct xe_device *xe = file_inode(f)->i_private;
+	u32 atomic_svm_timeslice_ms;
+	ssize_t ret;
+
+	ret = kstrtouint_from_user(ubuf, size, 0, &atomic_svm_timeslice_ms);
+	if (ret)
+		return ret;
+
+	xe->atomic_svm_timeslice_ms = atomic_svm_timeslice_ms;
+
+	return size;
+}
+
+static const struct file_operations atomic_svm_timeslice_ms_fops = {
+	.owner = THIS_MODULE,
+	.read = atomic_svm_timeslice_ms_show,
+	.write = atomic_svm_timeslice_ms_set,
+};
+
 void xe_debugfs_register(struct xe_device *xe)
 {
 	struct ttm_device *bdev = &xe->ttm;
@@ -211,6 +246,9 @@ void xe_debugfs_register(struct xe_device *xe)
 	debugfs_create_file("wedged_mode", 0600, root, xe,
 			    &wedged_mode_fops);
 
+	debugfs_create_file("atomic_svm_timeslice_ms", 0600, root, xe,
+			    &atomic_svm_timeslice_ms_fops);
+
 	for (mem_type = XE_PL_VRAM0; mem_type <= XE_PL_VRAM1; ++mem_type) {
 		man = ttm_manager_type(bdev, mem_type);
 
diff --git a/drivers/gpu/drm/xe/xe_device.c b/drivers/gpu/drm/xe/xe_device.c
index 75e753e0a682..7e620b11a9af 100644
--- a/drivers/gpu/drm/xe/xe_device.c
+++ b/drivers/gpu/drm/xe/xe_device.c
@@ -444,6 +444,7 @@ struct xe_device *xe_device_create(struct pci_dev *pdev,
 	xe->info.devid = pdev->device;
 	xe->info.revid = pdev->revision;
 	xe->info.force_execlist = xe_modparam.force_execlist;
+	xe->atomic_svm_timeslice_ms = 10;
 
 	err = xe_irq_init(xe);
 	if (err)
diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
index b9a892c44c67..6f5222f42410 100644
--- a/drivers/gpu/drm/xe/xe_device_types.h
+++ b/drivers/gpu/drm/xe/xe_device_types.h
@@ -567,6 +567,9 @@ struct xe_device {
 	/** @pmu: performance monitoring unit */
 	struct xe_pmu pmu;
 
+	/** @atomic_svm_timeslice_ms: Atomic SVM fault timeslice MS */
+	u32 atomic_svm_timeslice_ms;
+
 #ifdef TEST_VM_OPS_ERROR
 	/**
 	 * @vm_inject_error_position: inject errors at different places in VM
diff --git a/drivers/gpu/drm/xe/xe_svm.c b/drivers/gpu/drm/xe/xe_svm.c
index 121e39a2dd38..92aebb6b0902 100644
--- a/drivers/gpu/drm/xe/xe_svm.c
+++ b/drivers/gpu/drm/xe/xe_svm.c
@@ -780,7 +780,7 @@ int xe_svm_handle_pagefault(struct xe_vm *vm, struct xe_vma *vma,
 		.check_pages_threshold = IS_DGFX(vm->xe) &&
 			IS_ENABLED(CONFIG_DRM_XE_DEVMEM_MIRROR) ? SZ_64K : 0,
 		.vram_only = atomic,
-		.timeslice_ms = atomic ? 10 : 0,
+		.timeslice_ms = atomic ? vm->xe->atomic_svm_timeslice_ms : 0,
 	};
 	struct xe_svm_range *range;
 	struct drm_gpusvm_range *r;
-- 
2.34.1