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

[Nikita Shubin]

On Fri, 17 Apr 2020 16:24:21 -0600
Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> wrote:

> On Fri, 17 Apr 2020 at 11:27, Nikita Shubin
> <nikita.shubin@xxxxxxxxxxx> wrote:
> >
> > On Fri, 17 Apr 2020 11:01:22 -0600
> > Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> wrote:
> >
> > > On Thu, 16 Apr 2020 at 23:40, <nikita.shubin@xxxxxxxxxxx> wrote:
> > > >
> > > > Hi Mathieue,
> > > >
> > > > Hi Nikita,
> > > >
> > > > On Mon, Apr 06, 2020 at 02:33:08PM +0300,
> > > > nikita.shubin@xxxxxxxxxxx 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@xxxxxxxxxx>
> > > >
> > > >
> > > > 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?
> >
> > The reason is the following :
> >
> > remoteproc_core.c:
> > | rproc_fw_boot(struct rproc *rproc, const struct firmware *fw)
> > | rproc->bootaddr = rproc_get_boot_addr(rproc, fw);
> >
> > remoteproc_internal.h
> > | static inline
> > | u32 rproc_get_boot_addr(struct rproc *rproc, const struct firmware
> > *fw) | {
> > |       if (rproc->ops->get_boot_addr)
> > |               return rproc->ops->get_boot_addr(rproc, fw);
> > |
> > |       return 0;
> > | }
> 
> And as I said above the value of rproc->bootaddr is set to
> priv->bootreg in imx_rproc_stop().  What am I missing?  More over
> imx_rproc_ops doesn't have a ->load() function and as such rproc_alloc
> will set it to rproc_elf_get_boot_addr()

Yes, you are totally correct, it is not required in this patch thank you
for pointing this out.

> 
> >
> > >
> > > >
> > > >   };
> > > >
> > > >   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
> > > >
> >