[Intel-xe] [PATCH] drm/xe: Use nanoseconds instead of jiffies in uapi for user fence

[Zbigniew Kempczyński]

Using jiffies as a timeout from userspace is weird even it theoretically
exists possiblity of acquiring jiffies via getconf. Unfortunately this
method is unreliable and returned value may vary from configured in the
kernel config.

Change alters timeout to be expected in nanoseconds returning remaining
timeout for relative and elapsed for absolute.

Signed-off-by: Zbigniew Kempczyński <zbigniew.kempczynski at intel.com>
Cc: Andi Shyti <andi.shyti at linux.intel.com>
---
 drivers/gpu/drm/xe/xe_wait_user_fence.c | 39 +++++++++++++++++++------
 include/uapi/drm/xe_drm.h               |  5 +++-
 2 files changed, 34 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/xe/xe_wait_user_fence.c b/drivers/gpu/drm/xe/xe_wait_user_fence.c
index 6c8a60c60087..e0db0ba904ec 100644
--- a/drivers/gpu/drm/xe/xe_wait_user_fence.c
+++ b/drivers/gpu/drm/xe/xe_wait_user_fence.c
@@ -7,6 +7,7 @@
 
 #include <drm/drm_device.h>
 #include <drm/drm_file.h>
+#include <drm/drm_utils.h>
 #include <drm/xe_drm.h>
 
 #include "xe_device.h"
@@ -84,6 +85,24 @@ static int check_hw_engines(struct xe_device *xe,
 			 DRM_XE_UFENCE_WAIT_VM_ERROR)
 #define MAX_OP		DRM_XE_UFENCE_WAIT_LTE
 
+static unsigned long to_jiffies_timeout(struct drm_xe_wait_user_fence *args)
+{
+	unsigned long timeout;
+
+	if (args->flags & DRM_XE_UFENCE_WAIT_ABSTIME)
+		return drm_timeout_abs_to_jiffies(args->timeout);
+
+	if (args->timeout < 0)
+		return MAX_SCHEDULE_TIMEOUT;
+
+	if (args->timeout == 0)
+		return 0;
+
+	timeout = nsecs_to_jiffies(args->timeout);
+
+	return timeout ?: 1;
+}
+
 int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
 			     struct drm_file *file)
 {
@@ -98,7 +117,8 @@ int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
 	int err;
 	bool no_engines = args->flags & DRM_XE_UFENCE_WAIT_SOFT_OP ||
 		args->flags & DRM_XE_UFENCE_WAIT_VM_ERROR;
-	unsigned long timeout = args->timeout;
+	unsigned long timeout;
+	ktime_t start;
 
 	if (XE_IOCTL_ERR(xe, args->extensions) || XE_IOCTL_ERR(xe, args->pad) ||
 	    XE_IOCTL_ERR(xe, args->reserved[0] || args->reserved[1]))
@@ -149,8 +169,8 @@ int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
 		addr = vm->async_ops.error_capture.addr;
 	}
 
-	if (XE_IOCTL_ERR(xe, timeout > MAX_SCHEDULE_TIMEOUT))
-		return -EINVAL;
+	timeout = to_jiffies_timeout(args);
+	start = ktime_get();
 
 	/*
 	 * FIXME: Very simple implementation at the moment, single wait queue
@@ -194,12 +214,13 @@ int xe_wait_user_fence_ioctl(struct drm_device *dev, void *data,
 	else if (XE_IOCTL_ERR(xe, !timeout))
 		return -ETIME;
 
-	/*
-	 * Again very simple, return the time in jiffies that has past, may need
-	 * a more precision
-	 */
-	if (args->flags & DRM_XE_UFENCE_WAIT_ABSTIME)
-		args->timeout = args->timeout - timeout;
+	if (args->flags & DRM_XE_UFENCE_WAIT_ABSTIME) {
+		args->timeout = ktime_sub(ktime_get(), start);
+	} else {
+		args->timeout -= ktime_to_ns(ktime_sub(ktime_get(), start));
+		if (args->timeout < 0)
+			args->timeout = 0;
+	}
 
 	return 0;
 }
diff --git a/include/uapi/drm/xe_drm.h b/include/uapi/drm/xe_drm.h
index d5fc54b5be74..5c81e595c8bb 100644
--- a/include/uapi/drm/xe_drm.h
+++ b/include/uapi/drm/xe_drm.h
@@ -752,7 +752,10 @@ struct drm_xe_wait_user_fence {
 #define DRM_XE_UFENCE_WAIT_U32		0xffffffffu
 #define DRM_XE_UFENCE_WAIT_U64		0xffffffffffffffffu
 	__u64 mask;
-	/** @timeout: how long to wait before bailing, value in jiffies */
+	/**
+	 * @timeout: how long to wait before bailing, value in nanoseconds.
+	 * Returns timeout left for relative or elapsed for absolute.
+	 */
 	__s64 timeout;
 	/**
 	 * @num_engines: number of engine instances to wait on, must be zero
-- 
2.34.1