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

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

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On Tue, Jul 28, 2020 at 07:50:04AM +0000, Peng Fan wrote:
> > Subject: Re: [PATCH 00/10] remoteproc: imx_rproc: support iMX8M and early
> > boot
> > 
> > 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/loc
> > al_src/remoteproc-elf/linker.ld
> > https://git.pengutronix.de/cgit/ore/OSELAS.BSP-Pengutronix-DualKit/tree/loc
> > al_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 ;)
> 
> In NXP release, the m4 elf files have data/bss/heap/stack in the same
> data area, so the linker merged them into one segment and cause
> memsz > filesz.
> 
> I think I need to propose platform specific elf memset/memcpy,
> such as rproc_elf_memcpy, rproc_elf_memset,
> 
> To i.MX, need use memset_io and memcpy_toio, taking TCM
> as device memory.
> 
> Note: memset without io will cause abort when memsz>filesz.
> So use memset_io is safe.

Sounds good, i would prefer this way.

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