linux-kernel - Re: [PATCH v2 1/3] remoteproc: imx

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Date:   Tue, 14 Apr 2020 10:45:19 -0600
From:   Mathieu Poirier <mathieu.poirier@...aro.org>
To:     nikita.shubin@...uefel.me
Cc:     Nikita Shubin <NShubin@...con.com>,
        Ohad Ben-Cohen <ohad@...ery.com>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-remoteproc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/3] remoteproc: imx_rproc: set pc on start

Hi Nikita,

On Mon, Apr 06, 2020 at 02:33:08PM +0300, nikita.shubin@...uefel.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@...con.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?   

> +
>  	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
>