soc/mediatek: Flush cache before triggering EC reset

There will be no log in cbmem if we trigger ec reset on bootblock
stage. Therefore, call dcache_clean_all() before triggering ec
reset to flush cache to store logs on cbmem.

BUG=b:207743045
TEST=show logs on cbmem

Signed-off-by: Rex-BC Chen <rex-bc.chen@mediatek.com>
Change-Id: I1bd900beb4cc84f7121c5fb66907fa73b62517fa
Reviewed-on: https://review.coreboot.org/c/coreboot/+/59683
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Yu-Ping Wu <yupingso@google.com>
diff --git a/src/soc/mediatek/common/wdt.c b/src/soc/mediatek/common/wdt.c
index f06fbf0..6e1b761 100644
--- a/src/soc/mediatek/common/wdt.c
+++ b/src/soc/mediatek/common/wdt.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
 
+#include <arch/cache.h>
 #include <device/mmio.h>
 #include <console/console.h>
 #include <soc/wdt.h>
@@ -27,7 +28,10 @@
 		 * We trigger secondary reset by triggering WDT hardware to send signal to EC.
 		 * We do not use do_board_reset() to send signal to EC
 		 * which is controlled by software driver.
+		 * Before triggering secondary reset, clean the data cache so the logs in cbmem
+		 * console (either in SRAM or DRAM) can be flushed.
 		 */
+		dcache_clean_all();
 		write32(&mtk_wdt->wdt_mode, MTK_WDT_MODE_EXTEN | MTK_WDT_MODE_KEY);
 		write32(&mtk_wdt->wdt_swrst, MTK_WDT_SWRST_KEY);
 	} else if (wdt_sta & MTK_WDT_STA_SW_RST)