drm/panthor: Add an ioctl to query BO flags

This is useful when importing BOs, so we can know about cacheability
and flush the caches when needed.

We can also know when the buffer comes from a different subsystem and
take proper actions (avoid CPU mappings, or do kernel-based syncs
instead of userland cache flushes).

v2:
- New commit

v3:
- Add Steve's R-b

v4:
- No changes

v5:
- No changes

v6:
- No changes

v7:
- No changes

v8:
- No changes

Reviewed-by: Steven Price <steven.price@arm.com>
Link: https://patch.msgid.link/20251208100841.730527-6-boris.brezillon@collabora.com
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>

diff --git a/drivers/gpu/drm/panthor/panthor_drv.c b/drivers/gpu/drm/panthor/panthor_drv.c
index 2a9f1feac57adc583d375876ca36cd9f0fdfcffa..67d694d00ccb0fe04c11a6d20f23ea9c90241bac 100644 (file)
--- a/drivers/gpu/drm/panthor/panthor_drv.c
+++ b/drivers/gpu/drm/panthor/panthor_drv.c
@@ -1434,6 +1434,29 @@ err_ops:
        return ret;
 }
 
+static int panthor_ioctl_bo_query_info(struct drm_device *ddev, void *data,
+                                      struct drm_file *file)
+{
+       struct drm_panthor_bo_query_info *args = data;
+       struct panthor_gem_object *bo;
+       struct drm_gem_object *obj;
+
+       obj = drm_gem_object_lookup(file, args->handle);
+       if (!obj)
+               return -ENOENT;
+
+       bo = to_panthor_bo(obj);
+       args->pad = 0;
+       args->create_flags = bo->flags;
+
+       args->extra_flags = 0;
+       if (drm_gem_is_imported(&bo->base.base))
+               args->extra_flags |= DRM_PANTHOR_BO_IS_IMPORTED;
+
+       drm_gem_object_put(obj);
+       return 0;
+}
+
 static int
 panthor_open(struct drm_device *ddev, struct drm_file *file)
 {
@@ -1509,6 +1532,7 @@ static const struct drm_ioctl_desc panthor_drm_driver_ioctls[] = {
        PANTHOR_IOCTL(BO_SET_LABEL, bo_set_label, DRM_RENDER_ALLOW),
        PANTHOR_IOCTL(SET_USER_MMIO_OFFSET, set_user_mmio_offset, DRM_RENDER_ALLOW),
        PANTHOR_IOCTL(BO_SYNC, bo_sync, DRM_RENDER_ALLOW),
+       PANTHOR_IOCTL(BO_QUERY_INFO, bo_query_info, DRM_RENDER_ALLOW),
 };
 
 static int panthor_mmap(struct file *filp, struct vm_area_struct *vma)

diff --git a/include/uapi/drm/panthor_drm.h b/include/uapi/drm/panthor_drm.h
index 9f810305db6e08b5e8f65edc86e29abe4a7e5182..39d5ce8157423f5eb66cee1bb7d97d864dde2a6b 100644 (file)
--- a/include/uapi/drm/panthor_drm.h
+++ b/include/uapi/drm/panthor_drm.h
@@ -147,6 +147,13 @@ enum drm_panthor_ioctl_id {
 
        /** @DRM_PANTHOR_BO_SYNC: Sync BO data to/from the device */
        DRM_PANTHOR_BO_SYNC,
+
+       /**
+        * @DRM_PANTHOR_BO_QUERY_INFO: Query information about a BO.
+        *
+        * This is useful for imported BOs.
+        */
+       DRM_PANTHOR_BO_QUERY_INFO,
 };
 
 /**
@@ -1123,6 +1130,54 @@ struct drm_panthor_bo_sync {
        struct drm_panthor_obj_array ops;
 };
 
+/**
+ * enum drm_panthor_bo_extra_flags - Set of flags returned on a BO_QUERY_INFO request
+ *
+ * Those are flags reflecting BO properties that are not directly coming from the flags
+ * passed are creation time, or information on BOs that were imported from other drivers.
+ */
+enum drm_panthor_bo_extra_flags {
+       /**
+        * @DRM_PANTHOR_BO_IS_IMPORTED: BO has been imported from an external driver.
+        *
+        * Note that imported dma-buf handles are not flagged as imported if they
+        * where exported by panthor. Only buffers that are coming from other drivers
+        * (dma heaps, other GPUs, display controllers, V4L, ...).
+        *
+        * It's also important to note that all imported BOs are mapped cached and can't
+        * be considered IO-coherent even if the GPU is. This means they require explicit
+        * syncs that must go through the DRM_PANTHOR_BO_SYNC ioctl (userland cache
+        * maintenance is not allowed in that case, because extra operations might be
+        * needed to make changes visible to the CPU/device, like buffer migration when the
+        * exporter is a GPU with its own VRAM).
+        */
+       DRM_PANTHOR_BO_IS_IMPORTED = (1 << 0),
+};
+
+/**
+ * struct drm_panthor_bo_query_info - Query BO info
+ */
+struct drm_panthor_bo_query_info {
+       /** @handle: Handle of the buffer object to query flags on. */
+       __u32 handle;
+
+       /**
+        * @extra_flags: Combination of enum drm_panthor_bo_extra_flags flags.
+        */
+       __u32 extra_flags;
+
+       /**
+        * @create_flags: Flags passed at creation time.
+        *
+        * Combination of enum drm_panthor_bo_flags flags.
+        * Will be zero if the buffer comes from a different driver.
+        */
+       __u32 create_flags;
+
+       /** @pad: Will be zero on return. */
+       __u32 pad;
+};
+
 /**
  * DRM_IOCTL_PANTHOR() - Build a Panthor IOCTL number
  * @__access: Access type. Must be R, W or RW.
@@ -1171,6 +1226,8 @@ enum {
                DRM_IOCTL_PANTHOR(WR, SET_USER_MMIO_OFFSET, set_user_mmio_offset),
        DRM_IOCTL_PANTHOR_BO_SYNC =
                DRM_IOCTL_PANTHOR(WR, BO_SYNC, bo_sync),
+       DRM_IOCTL_PANTHOR_BO_QUERY_INFO =
+               DRM_IOCTL_PANTHOR(WR, BO_QUERY_INFO, bo_query_info),
 };
 
 #if defined(__cplusplus)