feat(mt8188): add DFD control in SiP service

DFD (Design for Debug) is a debugging tool, which scans flip-flops and
dumps to internal RAM on the WDT reset. After system reboots, those
values could be showed for debugging.

TEST=build pass.
BUG=b:244216434

Signed-off-by: Fengquan Chen <fengquan.chen@mediatek.corp-partner.google.com>
Change-Id: I468036131e941a46bc1ec12d33105146000730d8
diff --git a/plat/mediatek/drivers/dfd/dfd.c b/plat/mediatek/drivers/dfd/dfd.c
new file mode 100644
index 0000000..5770d50
--- /dev/null
+++ b/plat/mediatek/drivers/dfd/dfd.c
@@ -0,0 +1,43 @@
+/*
+ * Copyright (c) 2022, MediaTek Inc. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+#include <arch_helpers.h>
+#include <common/debug.h>
+#include <lib/mmio.h>
+#include <dfd.h>
+#include <mtk_sip_svc.h>
+#include <plat_dfd.h>
+
+static u_register_t dfd_smc_dispatcher(u_register_t arg0, u_register_t arg1,
+				       u_register_t arg2, u_register_t arg3,
+				       void *handle, struct smccc_res *smccc_ret)
+{
+	int ret = MTK_SIP_E_SUCCESS;
+
+	switch (arg0) {
+	case PLAT_MTK_DFD_SETUP_MAGIC:
+		INFO("[%s] DFD setup call from kernel\n", __func__);
+		dfd_setup(arg1, arg2, arg3);
+		break;
+	case PLAT_MTK_DFD_READ_MAGIC:
+		/* only allow to access DFD register base + 0x200 */
+		if (arg1 <= 0x200) {
+			ret = mmio_read_32(MISC1_CFG_BASE + arg1);
+		}
+		break;
+	case PLAT_MTK_DFD_WRITE_MAGIC:
+		/* only allow to access DFD register base + 0x200 */
+		if (arg1 <= 0x200) {
+			sync_writel(MISC1_CFG_BASE + arg1, arg2);
+		}
+		break;
+	default:
+		ret = MTK_SIP_E_INVALID_PARAM;
+		break;
+	}
+
+	return ret;
+}
+DECLARE_SMC_HANDLER(MTK_SIP_KERNEL_DFD, dfd_smc_dispatcher);