drm/nouveau/pmu/gk104: implement a hackish workaround for a hw bug

Only a handful of machines have this enabled by default, where it's been
proven to work.  The workaround can be explicitly enabled with a module
option also.

Still waiting on feedback from NVIDIA for a proper idea of exactly what
this fix is doing, and how to implement it properly.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

drivers/gpu/drm/nouveau/nvkm/subdev/pmu/gk104.c

@@ -26,9 +26,36 @@
 #include "priv.h"
 #include "fuc/gf110.fuc4.h"
 
+#include <core/device.h>
+#include <core/option.h>
+#include <subdev/timer.h>
+
+static void
+magic_(struct nvkm_pmu *pmu, u32 ctrl, int size)
+{
+	nv_wr32(pmu, 0x00c800, 0x00000000);
+	nv_wr32(pmu, 0x00c808, 0x00000000);
+	nv_wr32(pmu, 0x00c800, ctrl);
+	if (nv_wait(pmu, 0x00c800, 0x40000000, 0x40000000)) {
+		while (size--)
+			nv_wr32(pmu, 0x00c804, 0x00000000);
+	}
+	nv_wr32(pmu, 0x00c800, 0x00000000);
+}
+
+static void
+magic(struct nvkm_pmu *pmu, u32 ctrl)
+{
+	magic_(pmu, 0x8000a41f | ctrl, 6);
+	magic_(pmu, 0x80000421 | ctrl, 1);
+}
+
 static void
 gk104_pmu_pgob(struct nvkm_pmu *pmu, bool enable)
 {
+	struct nvkm_device *device = nv_device(pmu);
+	struct nvkm_object *dev = nv_object(device);
+
 	nv_mask(pmu, 0x000200, 0x00001000, 0x00000000);
 	nv_rd32(pmu, 0x000200);
 	nv_mask(pmu, 0x000200, 0x08000000, 0x08000000);
@@ -48,6 +75,30 @@ gk104_pmu_pgob(struct nvkm_pmu *pmu, bool enable)
 	nv_mask(pmu, 0x000200, 0x08000000, 0x00000000);
 	nv_mask(pmu, 0x000200, 0x00001000, 0x00001000);
 	nv_rd32(pmu, 0x000200);
+
+	if (nv_device_match(dev, 0x11fc, 0x17aa, 0x2211) /* Lenovo W541 */
+	 || nv_device_match(dev, 0x11fc, 0x17aa, 0x221e) /* Lenovo W541 */
+	 || nvkm_boolopt(device->cfgopt, "War00C800_0", false)) {
+		nv_info(pmu, "hw bug workaround enabled\n");
+		switch (device->chipset) {
+		case 0xe4:
+			magic(pmu, 0x04000000);
+			magic(pmu, 0x06000000);
+			magic(pmu, 0x0c000000);
+			magic(pmu, 0x0e000000);
+			break;
+		case 0xe6:
+			magic(pmu, 0x02000000);
+			magic(pmu, 0x04000000);
+			magic(pmu, 0x0a000000);
+			break;
+		case 0xe7:
+			magic(pmu, 0x02000000);
+			break;
+		default:
+			break;
+		}
+	}
 }
 
 struct nvkm_oclass *