Because MT8195 SCP core 0 and core 1 both boot from head of SRAM and
have the same viewpoint of SRAM, SCP has a "core 1 SRAM offset"
configuration to control the access destination of SCP core 1 to boot
core 1 from different SRAM location.

The "core 1 SRAM offset" configuration is composed by a range
and an offset. It works like a simple memory mapped mechanism.
When SCP core 1 accesses a SRAM address located in the range,
the SCP bus adds the configured offset to the address to
shift the physical destination address on SCP SRAM. This shifting is
transparent to the software running on SCP core 1.

Signed-off-by: Tinghan Shen <tinghan.shen@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/remoteproc/mtk_scp.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/drivers/remoteproc/mtk_scp.c b/drivers/remoteproc/mtk_scp.c
index be995c88d333..6d88b53fc07e 100644
--- a/drivers/remoteproc/mtk_scp.c
+++ b/drivers/remoteproc/mtk_scp.c
@@ -484,6 +484,9 @@ static int mt8195_scp_before_load(struct mtk_scp *scp)
 
 static int mt8195_scp_c1_before_load(struct mtk_scp *scp)
 {
+	u32 sec_ctrl;
+	struct mtk_scp *scp_c0;
+
 	scp_sram_power_on(scp->reg_base + MT8195_CPU1_SRAM_PD, 0);
 
 	/* hold SCP in reset while loading FW. */
@@ -492,6 +495,30 @@ static int mt8195_scp_c1_before_load(struct mtk_scp *scp)
 	/* enable MPU for all memory regions */
 	writel(0xff, scp->reg_base + MT8195_CORE1_MEM_ATT_PREDEF);
 
+	/*
+	 * The L2TCM_OFFSET_RANGE and L2TCM_OFFSET shift the destination address
+	 * on SRAM when SCP core 1 accesses SRAM.
+	 *
+	 * This configuration solves booting the SCP core 0 and core 1 from
+	 * different SRAM address because core 0 and core 1 both boot from
+	 * the head of SRAM by default. this must be configured before boot SCP core 1.
+	 *
+	 * The value of L2TCM_OFFSET_RANGE is from the viewpoint of SCP core 1.
+	 * When SCP core 1 issues address within the range (L2TCM_OFFSET_RANGE),
+	 * the address will be added with a fixed offset (L2TCM_OFFSET) on the bus.
+	 * The shift action is tranparent to software.
+	 */
+	writel(0, scp->reg_base + MT8195_L2TCM_OFFSET_RANGE_0_LOW);
+	writel(scp->sram_size, scp->reg_base + MT8195_L2TCM_OFFSET_RANGE_0_HIGH);
+
+	scp_c0 = list_first_entry(scp->cluster, struct mtk_scp, elem);
+	writel(scp->sram_phys - scp_c0->sram_phys, scp->reg_base + MT8195_L2TCM_OFFSET);
+
+	/* enable SRAM offset when fetching instruction and data */
+	sec_ctrl = readl(scp->reg_base + MT8195_SEC_CTRL);
+	sec_ctrl |= MT8195_CORE_OFFSET_ENABLE_I | MT8195_CORE_OFFSET_ENABLE_D;
+	writel(sec_ctrl, scp->reg_base + MT8195_SEC_CTRL);
+
 	return 0;
 }
 
-- 
2.18.0