Re: [PATCH 00/10] remoteproc: imx_rproc: support iMX8M and early boot

[Oleksij Rempel <o.rempel@pengutronix.de>]

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On Mon, Jul 27, 2020 at 09:18:31AM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH 00/10] remoteproc: imx_rproc: support iMX8M and early
> > boot
> > 
> > On Mon, Jul 27, 2020 at 06:44:32AM +0000, Peng Fan wrote:
> > > Hi Oleksij,
> > >
> > > > Subject: Re: [PATCH 00/10] remoteproc: imx_rproc: support iMX8M and
> > > > early boot
> > > >
> > > > Hi,
> > > >
> > > > On Fri, Jul 24, 2020 at 04:08:03PM +0800, Peng Fan wrote:
> > > > > This patchset is to support i.MX8MQ/M coproc booted before linux.
> > > > > Since i.MX8MQ/M was not supported, several patches are needed to
> > > > > first support the platform, then support early boot case.
> > > > >
> > > > > I intended to included i.MX8QM/QXP, but that would introduce a
> > > > > large patchset, so not included. But the clk/syscon optional patch
> > > > > for i.MX8QM/QXP was still kept here to avoid rebase error.
> > > >
> > > > Thank you for your work.
> > > >
> > > > Can you please provide more information about big picture of this work.
> > > >
> > > > If I see it correctly, we have here support for i.MX8MM, which seems
> > > > to be able to fully control Cortex M4 (enable CPU core, etc...).
> > >
> > > Yes.
> > 
> > In this case, I would recommend to mainline the i.MX8MM part
> > first/separately.
> 
> Only the last patch is to support earlyboot, all others is imx8mm part.

ok

> > 
> > > >
> > > > And other case, where remoteproc is running on application processor
> > > > and can't or should not touch M4 (i.MX7ULP, i.MX8QM/QXP..). Since M4
> > > > provides some functionality, you are trying to reuse remoteproc
> > > > framework to get resource table present in ELF header and to
> > > > dynamically load things. For some reasons this header provides more
> > > > information then needed, so you are changing the ELF parser in the kernel
> > to workaround it.
> > >
> > > Not exactly.
> > >
> > > For i.MX8MM, we support two cases. M4 kicked by U-Boot, M4 kicked by
> > Linux remoteproc.
> > > For i.MX8QM/QXP, the typical usecase is M4 kicked by SCFW, but we will
> > > also add M4 kicked by Linux remoteproc.
> > > For i.MX7ULP, I would only support M4 dual boot case, M4 control
> > everything.
> > 
> > From current state of discussion, i'm not sure what role plays remoteproc in
> > the scenario where M4 is started before linux. Especially if we are not using
> > resource table.
> 
> We are using resource table from an address, not in elf file.
> This is the new feature in Linux-next to support coproc booted early.
> 
> > 
> > > The reason the change the elf parser is that when M4 elf is loaded by
> > > Linux remoteproc, It use memset to clear area.
> > 
> > The use of memset, depends on ELF format. Fix/change the linker script on
> > your firmware and memset will be never called.
> > 
> > > However we use ioremap, memset on ARM64 will report crash to device
> > > nGnRE memory. And we could not use ioremap_wc to TCM area, since it
> > > could have data correctly written into TCM.
> > 
> > I have strong feeling, that we are talking about badly or not properly
> > formatted ELF binary. I would prefer to double check it, before we will apply
> > fixes on wrong place.
> > 
> > > Maintainer not wanna to drop memset in common code, and TI guys
> > > suggest add i.MX specific elf stuff. So I add elf handler in i.MX code.
> > 
> > I think, removing memset may damage current users of imx_rproc driver.
> > Since, like I said: the use of memset depends on ELF format.
> 
> In my elf file, the last PT_LOAD contains data/bss/heap/stack. I'll check
> with our MCU guys, we only need the specific data loaded.
> 
> Elf file type is EXEC (Executable file)
> Entry point 0x1ffe0355
> There are 3 program headers, starting at offset 52
> 
> Program Headers:
>   Type           Offset   VirtAddr   PhysAddr   FileSiz MemSiz  Flg Align
>   LOAD           0x010000 0x1ffe0000 0x1ffe0000 0x00240 0x00240 R   0x10000
>   LOAD           0x010240 0x1ffe0240 0x1ffe0240 0x03e90 0x03e90 RWE 0x10000
>   LOAD           0x020000 0x20000000 0x1ffe40d0 0x00068 0x0ad00 RW  0x10000
> 
>  Section to Segment mapping:
>   Segment Sections...
>    00     .interrupts
>    01     .resource_table .text .ARM .init_array .fini_array
>    02     .data .bss .heap .stack

Here is an example of formatting ELF for remoteproc:
https://git.pengutronix.de/cgit/ore/OSELAS.BSP-Pengutronix-DualKit/tree/local_src/remoteproc-elf/linker.ld
https://git.pengutronix.de/cgit/ore/OSELAS.BSP-Pengutronix-DualKit/tree/local_src/remoteproc-elf/imx7m4.S

In this example I pack linux in to remoteproc elf image and start linux
on imx7d-m4 part.
Will be interesting if you can do the same on imx8* SoCs ;)

Regards,
Oleksij
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