RE: [PATCH V2 5/6] remoteproc: imx_rproc: set Cortex-M stack/pc to TCML

[Peng Fan]

> Subject: Re: [PATCH V2 5/6] remoteproc: imx_rproc: set Cortex-M stack/pc
> to TCML
> 
> On Fri, Jan 27, 2023 at 05:22:45PM +0800, Peng Fan (OSS) wrote:
> > From: Peng Fan <peng.fan@xxxxxxx>
> >
> > The i.MX8M Cortex-M core not has ROM. It has a requirement is the
> > stack, pc value should be set in address 0 and 4 from the view of
> > itself. From Cortex-A core view, the region is at TCML start address.
> >
> > The stack and pc value are the first two words stored in section
> > ".interrupts" of the firmware, and the section is the first section in
> > the firmware.
> >
> > When the firmware is built to run in TCML, there is no issue, because
> > when copying elf segments, the first two words are copied to TCML also.
> >
> > However when the firmware is built ro run in DDR, the first two words
> > are not copied to TCML start address.
> >
> > This patch is to find the ".interrupts" section, read out the first
> > two words and write to TCML start address at offset 0 and 4.
> >
> > Signed-off-by: Peng Fan <peng.fan@xxxxxxx>
> > ---
> >  drivers/remoteproc/imx_rproc.c | 37
> > +++++++++++++++++++++++++++++++++-
> >  1 file changed, 36 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/remoteproc/imx_rproc.c
> > b/drivers/remoteproc/imx_rproc.c index 295e0e0e869a..f5ee0c9bb09d
> > 100644
> > --- a/drivers/remoteproc/imx_rproc.c
> > +++ b/drivers/remoteproc/imx_rproc.c
> > @@ -7,6 +7,7 @@
> >  #include <linux/arm-smccc.h>
> >  #include <linux/clk.h>
> >  #include <linux/err.h>
> > +#include <linux/firmware.h>
> >  #include <linux/firmware/imx/sci.h>
> >  #include <linux/interrupt.h>
> >  #include <linux/kernel.h>
> > @@ -23,6 +24,7 @@
> >  #include <linux/workqueue.h>
> >
> >  #include "imx_rproc.h"
> > +#include "remoteproc_elf_helpers.h"
> >  #include "remoteproc_internal.h"
> >
> >  #define IMX7D_SRC_SCR			0x0C
> > @@ -634,6 +636,39 @@ static struct resource_table
> *imx_rproc_get_loaded_rsc_table(struct rproc *rproc
> >  	return (struct resource_table __force *)priv->rsc_table;  }
> >
> > +static u64 imx_rproc_get_boot_addr(struct rproc *rproc, const struct
> > +firmware *fw) {
> > +	struct imx_rproc *priv = rproc->priv;
> > +	const u8 *elf_data = (void *)fw->data;
> > +	u8 class = fw_elf_get_class(fw);
> > +	u64 bootaddr = rproc_elf_get_boot_addr(rproc, fw);
> > +	const void *shdr;
> > +	void __iomem *va;
> > +	u64 sh_addr, offset;
> > +
> > +	if (priv->dcfg->devtype == IMX_RPROC_IMX8M) {
> > +		/*
> > +		 * i.MX8M Cortex-M requires [stack, pc] be put in address
> > +		 * [0, 4], so the da address is 0, size is 8 words.
> > +		 */
> > +		va = (__force void __iomem *)rproc_da_to_va(rproc, 0, 8,
> NULL);
> > +		shdr = rproc_elf_find_shdr(rproc, fw, ".interrupts");
> > +		if (!shdr || !va)
> > +			return bootaddr;
> > +		sh_addr = elf_shdr_get_sh_addr(class, shdr);
> 
> This isn't used - why is it still there?

will drop it.

> 
> > +		offset = elf_shdr_get_sh_offset(class, shdr);
> > +
> > +		/*
> > +		 * Write stack, pc to TCML start address. The TCML region
> > +		 * is marked with ATT_IOMEM, so use writel.
> > +		 */
> > +		writel(*(u32 *)(elf_data + offset), va);
> > +		writel(*(u32 *)(elf_data + offset + 4), va + 4);
> 
> Here you are writing 2 words at address 0x0 and 2 words at address 0x4.
> Why are you saying the size is 8 words in the comment above?

Typo. I should mean 8 bytes.

Thanks,
Peng.

> 
> > +	}
> > +
> > +	return bootaddr;
> > +}
> > +
> >  static const struct rproc_ops imx_rproc_ops = {
> >  	.prepare	= imx_rproc_prepare,
> >  	.attach		= imx_rproc_attach,
> > @@ -647,7 +682,7 @@ static const struct rproc_ops imx_rproc_ops = {
> >  	.find_loaded_rsc_table = rproc_elf_find_loaded_rsc_table,
> >  	.get_loaded_rsc_table = imx_rproc_get_loaded_rsc_table,
> >  	.sanity_check	= rproc_elf_sanity_check,
> > -	.get_boot_addr	= rproc_elf_get_boot_addr,
> > +	.get_boot_addr	= imx_rproc_get_boot_addr,
> >  };
> >
> >  static int imx_rproc_addr_init(struct imx_rproc *priv,
> > --
> > 2.37.1
> >