drm/asahi: It begins (in Rust)

This implements basic RTKit bring-up and UAT page table management.

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

drivers/gpu/drm/Kconfig

@@ -418,6 +418,8 @@ source "drivers/gpu/drm/sprd/Kconfig"
 
 source "drivers/gpu/drm/apple/Kconfig"
 
+source "drivers/gpu/drm/asahi/Kconfig"
+
 config DRM_HYPERV
 	tristate "DRM Support for Hyper-V synthetic video device"
 	depends on DRM && PCI && MMU && HYPERV

drivers/gpu/drm/Makefile

@@ -149,3 +149,4 @@ obj-y			+= gud/
 obj-$(CONFIG_DRM_HYPERV) += hyperv/
 obj-y			+= solomon/
 obj-$(CONFIG_DRM_SPRD) += sprd/
+obj-$(CONFIG_DRM_ASAHI) += asahi/

drivers/gpu/drm/asahi/Kconfig

@@ -0,0 +1,14 @@
+# SPDX-License-Identifier: GPL-2.0
+
+config DRM_ASAHI
+	tristate "Asahi (DRM support for Apple AGX GPUs)"
+	depends on RUST
+	depends on DRM
+	depends on (ARM64 && ARCH_APPLE) || (COMPILE_TEST && !GENERIC_ATOMIC64)
+	depends on MMU
+	select DRM_SCHED
+	select IOMMU_SUPPORT
+	select IOMMU_IO_PGTABLE_LPAE
+	select DRM_GEM_SHMEM_HELPER
+	help
+	  DRM driver for Apple AGX GPUs (G13x, found in the M1 SoC family)

drivers/gpu/drm/asahi/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+
+asahi-y := \
+	asahi_drv.o \
+	asahi_mmu.o
+
+obj-$(CONFIG_DRM_ASAHI) += asahi.o

drivers/gpu/drm/asahi/asahi_drv.rs

@@ -0,0 +1,105 @@
+// SPDX-License-Identifier: GPL-2.0-only OR MIT
+
+//! Driver for the Apple AGX GPUs found in Apple Silicon SoCs.
+
+use kernel::{
+    bindings, device,
+    error::{to_result, Result},
+    io_mem::IoMem,
+    module_platform_driver, of, platform,
+    prelude::*,
+    soc::apple::rtkit,
+    sync::smutex::Mutex,
+    sync::{Arc, ArcBorrow},
+};
+
+const ASC_CTL_SIZE: usize = 0x4000;
+const CPU_CONTROL: usize = 0x44;
+const CPU_RUN: u32 = 0x1 << 4; // BIT(4)
+
+struct AsahiData {
+    dev: device::Device,
+    rtkit: Mutex<Option<rtkit::RTKit<AsahiDevice>>>,
+}
+
+struct AsahiResources {
+    asc: IoMem<ASC_CTL_SIZE>,
+}
+
+type DeviceData = device::Data<(), AsahiResources, AsahiData>;
+
+struct AsahiDevice;
+
+impl AsahiDevice {
+    fn start_cpu(data: ArcBorrow<'_, DeviceData>) -> Result {
+        let res = data.resources().ok_or(ENXIO)?;
+        let val = res.asc.readl_relaxed(CPU_CONTROL);
+
+        res.asc.writel_relaxed(val | CPU_RUN, CPU_CONTROL);
+
+        Ok(())
+    }
+}
+
+#[vtable]
+impl rtkit::Operations for AsahiDevice {
+    type Data = ();
+}
+
+extern "C" {
+    pub fn asahi_mmu_init(dev: *mut bindings::device) -> core::ffi::c_int;
+}
+
+impl platform::Driver for AsahiDevice {
+    type Data = Arc<DeviceData>;
+
+    kernel::define_of_id_table! {(), [
+        (of::DeviceId::Compatible(b"apple,agx-t8103"), None),
+    ]}
+
+    fn probe(
+        pdev: &mut platform::Device,
+        _id_info: Option<&Self::IdInfo>,
+    ) -> Result<Arc<DeviceData>> {
+        let dev = device::Device::from_dev(pdev);
+
+        dev_info!(dev, "probing!\n");
+
+        // TODO: add device abstraction to ioremap by name
+        // SAFETY: AGX does DMA via the UAT IOMMU (mostly)
+        let asc_reg = unsafe { pdev.ioremap_resource(0)? };
+
+        let data = kernel::new_device_data!(
+            (),
+            AsahiResources {
+                // SAFETY: This device does DMA via the UAT IOMMU.
+                asc: asc_reg,
+            },
+            AsahiData {
+                dev: dev,
+                rtkit: Mutex::new(None),
+            },
+            "Asahi::Registrations"
+        )?;
+
+        let data = Arc::<DeviceData>::from(data);
+
+        AsahiDevice::start_cpu(data.as_ref_borrow())?;
+
+        to_result(unsafe { asahi_mmu_init((&data.dev as &dyn device::RawDevice).raw_device()) })?;
+
+        let mut rtkit = unsafe { rtkit::RTKit::<AsahiDevice>::new(&data.dev, None, 0, ()) }?;
+
+        rtkit.boot()?;
+        *data.rtkit.lock() = Some(rtkit);
+
+        dev_info!(data.dev, "probed!\n");
+        Ok(data)
+    }
+}
+
+module_platform_driver! {
+    type: AsahiDevice,
+    name: "asahi",
+    license: "Dual MIT/GPL",
+}