drm/amd/powerplay: revise caching the soft pptable and add it's size

This fixes a bug in the pptable access interface that could lead to
a crash.  Check the pointer before using it.
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Eric Huang <JinHuiEric.Huang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/powerplay/hwmgr/tonga_processpptables.c

@@ -138,12 +138,15 @@ const void *get_powerplay_table(struct pp_hwmgr *hwmgr)
 
 	u16 size;
 	u8 frev, crev;
-	void *table_address;
+	void *table_address = (void *)hwmgr->soft_pp_table;
 
+	if (!table_address) {
 		table_address = (ATOM_Tonga_POWERPLAYTABLE *)
-		cgs_atom_get_data_table(hwmgr->device, index, &size, &frev, &crev);
-
+				cgs_atom_get_data_table(hwmgr->device,
+						index, &size, &frev, &crev);
 		hwmgr->soft_pp_table = table_address;	/*Cache the result in RAM.*/
+		hwmgr->soft_pp_table_size = size;
+	}
 
 	return table_address;
 }

drivers/gpu/drm/amd/powerplay/inc/hwmgr.h

@@ -577,6 +577,7 @@ struct pp_hwmgr {
 	void *device;
 	struct pp_smumgr *smumgr;
 	const void *soft_pp_table;
+	uint32_t soft_pp_table_size;
 	bool need_pp_table_upload;
 	enum amd_dpm_forced_level dpm_level;
 	bool block_hw_access;