remoteproc/mediatek: enable MPU for all memory regions in MT8192 SCP

The register MT8192_CORE0_MEM_ATT_PREDEF contains attributes for each
memory region.  It defines whether a memory region can be managed by MPU
or not.

In the past, due to the default settings in the register, MT8192 SCP
works luckily.  After enabling L1TCM, SCP starts to access memory region
that is not included in the default settings.  As a result, SCP hangs.

Enables MPU for all memory regions in MT8192 SCP.

Note that the register is read only once when SCP resets.  Thus, it must
be set from kernel side.
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20210127083136.3745652-3-tzungbi@google.comSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/remoteproc/mtk_common.h

@@ -47,6 +47,7 @@
 
 #define MT8192_CORE0_SW_RSTN_CLR	0x10000
 #define MT8192_CORE0_SW_RSTN_SET	0x10004
+#define MT8192_CORE0_MEM_ATT_PREDEF	0x10008
 #define MT8192_CORE0_WDT_IRQ		0x10030
 #define MT8192_CORE0_WDT_CFG		0x10034
 

drivers/remoteproc/mtk_scp.c

@@ -371,6 +371,9 @@ static int mt8192_scp_before_load(struct mtk_scp *scp)
 	mt8192_power_on_sram(scp->reg_base + MT8192_L1TCM_SRAM_PDN);
 	mt8192_power_on_sram(scp->reg_base + MT8192_CPU0_SRAM_PD);
 
+	/* enable MPU for all memory regions */
+	writel(0xff, scp->reg_base + MT8192_CORE0_MEM_ATT_PREDEF);
+
 	return 0;
 }