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

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Date:   Fri, 17 Apr 2020 11:01:22 -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-remoteproc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] remoteproc: imx_rproc: set pc on start

On Thu, 16 Apr 2020 at 23:40, <nikita.shubin@...uefel.me> wrote:
>
> Hi Mathieue,
>
> 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.
>
> Noted and will be fixed.
>
>  ---
>   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?
>
> Yes, my bad, it is also needed for IMX6 (but even so i need to study this topic more carefully),
> this should be applied exclusively for imx7d for now, and if will be needed someone
> with imx6 hardware to test on can extend this on imx6 also.
>
>
>
>
>  +
>           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() ?
>
> The priv->bootreg is the address where we are writing Entry Point and it is fixed,
> 0x04 address is translated to 0x00180004, so don't quite understand you we
> are writing rproc->bootaddr into priv->bootreg, not wiseversa.
>

What is your reason to set ops->get_boot_addr ?  How does that help
the work done in this patch?

>
>   };
>
>   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
>