drm/nouveau/gr/gp107,gp108: implement workaround for HW hanging during init

{

	struct gf100_gr *gr = gf100_gr(base);

	struct nvkm_subdev *subdev = &base->engine.subdev;

	struct nvkm_device *device = subdev->device;

	bool reset = device->chipset == 0x137 || device->chipset == 0x138;

	u32 ret;

	/* On certain GP107/GP108 boards, we trigger a weird issue where

	 * GR will stop responding to PRI accesses after we've asked the

	 * SEC2 RTOS to boot the GR falcons.  This happens with far more

	 * frequency when cold-booting a board (ie. returning from D3).

	 *

	 * The root cause for this is not known and has proven difficult

	 * to isolate, with many avenues being dead-ends.

	 *

	 * A workaround was discovered by Karol, whereby putting GR into

	 * reset for an extended period right before initialisation

	 * prevents the problem from occuring.

	 *

	 * XXX: As RM does not require any such workaround, this is more

	 *      of a hack than a true fix.

	 */

	reset = nvkm_boolopt(device->cfgopt, "NvGrResetWar", reset);

	if (reset) {

		nvkm_mask(device, 0x000200, 0x00001000, 0x00000000);

		nvkm_rd32(device, 0x000200);

		msleep(50);

		nvkm_mask(device, 0x000200, 0x00001000, 0x00001000);

		nvkm_rd32(device, 0x000200);

	}

	nvkm_pmu_pgob(gr->base.engine.subdev.device->pmu, false);

	ret = nvkm_falcon_get(&gr->fecs.falcon, subdev);