drm/lima: set gp bus_stop bit before hard reset

This is required for reliable hard resets. Otherwise, doing a hard reset
while a task is still running (such as a task which is being stopped by
the drm_sched timeout handler) may result in random mmu write timeouts
or lockups which cause the entire gpu to hang.
Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Signed-off-by: Qiang Yu <yuq825@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240124025947.2110659-5-nunes.erico@gmail.com

drivers/gpu/drm/lima/lima_gp.c

@@ -166,6 +166,11 @@ static void lima_gp_task_run(struct lima_sched_pipe *pipe,
 	gp_write(LIMA_GP_CMD, cmd);
 }
 
+static int lima_gp_bus_stop_poll(struct lima_ip *ip)
+{
+	return !!(gp_read(LIMA_GP_STATUS) & LIMA_GP_STATUS_BUS_STOPPED);
+}
+
 static int lima_gp_hard_reset_poll(struct lima_ip *ip)
 {
 	gp_write(LIMA_GP_PERF_CNT_0_LIMIT, 0xC01A0000);
@@ -179,6 +184,13 @@ static int lima_gp_hard_reset(struct lima_ip *ip)
 
 	gp_write(LIMA_GP_PERF_CNT_0_LIMIT, 0xC0FFE000);
 	gp_write(LIMA_GP_INT_MASK, 0);
+
+	gp_write(LIMA_GP_CMD, LIMA_GP_CMD_STOP_BUS);
+	ret = lima_poll_timeout(ip, lima_gp_bus_stop_poll, 10, 100);
+	if (ret) {
+		dev_err(dev->dev, "%s bus stop timeout\n", lima_ip_name(ip));
+		return ret;
+	}
 	gp_write(LIMA_GP_CMD, LIMA_GP_CMD_RESET);
 	ret = lima_poll_timeout(ip, lima_gp_hard_reset_poll, 10, 100);
 	if (ret) {