Re: [PATCH v2 1/3] remoteproc: imx_rproc: set pc on start

[Nikita Shubin <nikita.shubin@maquefel.me>]

On Tue, 14 Apr 2020 10:45:19 -0600
Mathieu Poirier <mathieu.poirier@linaro.org> wrote:

> Hi Nikita,
> 
> On Mon, Apr 06, 2020 at 02:33:08PM +0300, nikita.shubin@maquefel.me
> wrote:
> > 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@topcon.com>
> 
> The address in the SoB has to match what is found in the "From:"
> field of the email header.  Checkpatch is complaining about that,
> something I would have expected to be fixed before sending this set
> out.
> 
> > ---
> >  drivers/remoteproc/imx_rproc.c | 16 +++++++++++++++-
> >  1 file changed, 15 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/remoteproc/imx_rproc.c
> > b/drivers/remoteproc/imx_rproc.c index 3e72b6f38d4b..bebc58d0f711
> > 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);
> 
> What happens on all the other IMX systems where this fix is not
> needed?  Will they continue to work properly?   

Mathieu you are totally correct imx6/imx7 use different addresses they
boot.

For imx7:
| On i.MX 7Dual/7Solo, the boot vector for the Cortex-M4 core is located
| at the start of the OCRAM_S (On Chip RAM - Secure) whose address is
| 0x0018_0000 from Cortex-A7.

For imx6:
| The Boot vector for the Cortex-M4 core is located at the start of the
| TCM_L whose address is 0x007F_8000 from the Cortex-A9. This is a
| different location than on the i.MX 7Dual/7Solo

But on imx7 0x0 is translated to 0x0018_0000 by imx_rproc_da_to_va, and
on imx7 0x0 is translated to 0x007F_8000, using imx_rproc_att_imx7d and 
imx_rproc_att_imx6sx respectively.

I have no information about IMX8 (i have found none available
publicity), but should be the same as Cortex-M boots from 0x0.

> 
> > +
> >  	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;
> >  }
> >  
> > @@ -243,7 +254,8 @@ static void *imx_rproc_da_to_va(struct rproc
> > *rproc, u64 da, int len) static const struct rproc_ops
> > imx_rproc_ops = { .start		= imx_rproc_start,
> >  	.stop		= imx_rproc_stop,
> > -	.da_to_va       = imx_rproc_da_to_va,
> > +	.da_to_va	= imx_rproc_da_to_va,
> > +	.get_boot_addr	= rproc_elf_get_boot_addr,
> 
> How is this useful?  Sure it will set rproc->bootaddr in
> rproc_fw_boot() but what good does that do when it is invariably set
> again in imx_rproc_start() ? 
> 
> >  };
> >  
> >  static int imx_rproc_addr_init(struct imx_rproc *priv,
> > @@ -360,6 +372,8 @@ 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.
> > -- 
> > 2.25.1
> >