drm/asahi: Implement ASAHI_GET_TIME

Signed-off-by: Asahi Lina <lina@asahilina.net>

Author: hoshinolina

drivers/gpu/drm/asahi/driver.rs

@@ -84,6 +84,8 @@ impl drv::Driver for AsahiDriver {
             ioctl::AUTH | ioctl::RENDER_ALLOW, crate::file::File::queue_destroy),
         (ASAHI_SUBMIT,          drm_asahi_submit,
             ioctl::AUTH | ioctl::RENDER_ALLOW, crate::file::File::submit),
+        (ASAHI_GET_TIME,        drm_asahi_get_time,
+            ioctl::AUTH | ioctl::RENDER_ALLOW, crate::file::File::get_time),
     }
 }
 

drivers/gpu/drm/asahi/file.rs

@@ -241,7 +241,7 @@ impl File {
             unstable_uabi_version: uapi::DRM_ASAHI_UNSTABLE_UABI_VERSION,
             pad0: 0,
 
-            feat_compat: gpu.get_cfg().gpu_feat_compat,
+            feat_compat: gpu.get_cfg().gpu_feat_compat | hw::feat::compat::GETTIME,
             feat_incompat: gpu.get_cfg().gpu_feat_incompat,
 
             gpu_generation: gpu.get_dyncfg().id.gpu_gen as u32,
@@ -959,6 +959,33 @@ impl File {
             Ok(()) => Ok(0),
         }
     }
+
+    /// IOCTL: get_time: Get the current GPU timer value.
+    pub(crate) fn get_time(
+        _device: &AsahiDevice,
+        _dev_data: <Self as drm::file::DriverFile>::BorrowedData<'_>,
+        data: &mut uapi::drm_asahi_get_time,
+        _file: &DrmFile,
+    ) -> Result<u32> {
+        if data.extensions != 0 || data.flags != 0 {
+            cls_pr_debug!(Errors, "get_time: Unexpected extensions or flags\n");
+            return Err(EINVAL);
+        }
+
+        let gputime: u64;
+
+        // SAFETY: Assembly only loads the timer
+        unsafe {
+            core::arch::asm!(
+                "mrs {x}, CNTPCT_EL0",
+                x = out(reg) gputime
+            );
+        }
+
+        data.gpu_timestamp = gputime;
+
+        Ok(0)
+    }
 }
 
 impl Drop for File {

drivers/gpu/drm/asahi/hw/mod.rs

@@ -94,6 +94,8 @@ pub(crate) mod feat {
         /// Soft MMU faults enabled.
         pub(crate) const SOFT_FAULTS: u64 =
             uapi::drm_asahi_feat_compat_DRM_ASAHI_FEAT_SOFT_FAULTS as u64;
+        /// GETTIME API supported
+        pub(crate) const GETTIME: u64 = uapi::drm_asahi_feat_compat_DRM_ASAHI_FEAT_GETTIME as u64;
     }
 
     /// Backwards-incompatible features.