[PATCH 2/2] remoteproc: imx_rproc: set pc on start

[Nikita Shubin <NShubin@xxxxxxxxxx>]

In case elf file interrupt vector is not supposed to be at OCRAM_S,
it is needed to write elf entry point to OCRAM_S + 0x4, to boot M4
firmware.

Otherwise firmware located anywhere besides OCRAM_S won't boot.

The firmware must set stack poiner as first instruction:

Reset_Handler:
    ldr   sp, = __stack      /* set stack pointer */

Signed-off-by: Nikita Shubin <NShubin@xxxxxxxxxx>
---
 drivers/remoteproc/imx_rproc.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/remoteproc/imx_rproc.c b/drivers/remoteproc/imx_rproc.c
index 796b6b86550a..d02007f05ebd 100644
--- a/drivers/remoteproc/imx_rproc.c
+++ b/drivers/remoteproc/imx_rproc.c
@@ -45,6 +45,8 @@
 
 #define IMX7D_RPROC_MEM_MAX		8
 
+#define IMX_BOOT_PC			0x4
+
 /**
  * struct imx_rproc_mem - slim internal memory structure
  * @cpu_addr: MPU virtual address of the memory region
@@ -85,6 +87,7 @@ struct imx_rproc {
 	const struct imx_rproc_dcfg	*dcfg;
 	struct imx_rproc_mem		mem[IMX7D_RPROC_MEM_MAX];
 	struct clk			*clk;
+	void __iomem			*bootreg;
 };
 
 static const struct imx_rproc_att imx_rproc_att_imx7d[] = {
@@ -162,11 +165,16 @@ static int imx_rproc_start(struct rproc *rproc)
 	struct device *dev = priv->dev;
 	int ret;
 
+	/* write entry point to program counter */
+	writel(rproc->bootaddr, priv->bootreg);
+
 	ret = regmap_update_bits(priv->regmap, dcfg->src_reg,
 				 dcfg->src_mask, dcfg->src_start);
 	if (ret)
 		dev_err(dev, "Failed to enable M4!\n");
 
+	dev_info(&rproc->dev, "Started from 0x%x\n", rproc->bootaddr);
+
 	return ret;
 }
 
@@ -182,6 +190,9 @@ static int imx_rproc_stop(struct rproc *rproc)
 	if (ret)
 		dev_err(dev, "Failed to stop M4!\n");
 
+	/* clear entry points */
+	writel(0, priv->bootreg);
+
 	return ret;
 }
 
@@ -366,6 +377,8 @@ static int imx_rproc_probe(struct platform_device *pdev)
 		goto err_put_rproc;
 	}
 
+	priv->bootreg = imx_rproc_da_to_va(rproc, IMX_BOOT_PC, sizeof(u32));
+
 	/*
 	 * clk for M4 block including memory. Should be
 	 * enabled before .start for FW transfer.
-- 
2.24.1