drm/asahi: Implement ASAHI_GET_TIME

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

Author: hoshinolina

drivers/gpu/drm/asahi/driver.rs

@@ -76,6 +76,8 @@ 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

@@ -925,6 +925,38 @@ impl File {
             Ok(_) => Ok(0),
         }
     }
+
+    /// IOCTL: get_time: Get the current GPU timer value.
+    pub(crate) fn get_time(
+        device: &AsahiDevice,
+        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 mut tp: kernel::bindings::timespec64 = Default::default();
+        let mut gputime: u64 = 0;
+
+        // TODO: bindings
+        // SAFETY: These functions are safe to call as long as the argument pointer is valid
+        unsafe {
+            core::arch::asm!(
+                "mrs {x}, CNTPCT_EL0",
+                x = out(reg) gputime
+            );
+            kernel::bindings::ktime_get_raw_ts64(&mut tp);
+            kernel::bindings::timens_add_monotonic(&mut tp);
+        }
+
+        data.gpu_timestamp = gputime;
+        data.tv_sec = tp.tv_sec;
+        data.tv_nsec = tp.tv_nsec;
+
+        Ok(0)
+    }
 }
 
 impl Drop for File {