Hi Bjorn, > Subject: Re: [PATCH 1/2] remoteproc: drop memset when loading elf > segments > > On Thu 09 Apr 01:22 PDT 2020, Peng Fan wrote: > > > To arm64, "dc zva, dst" is used in memset. > > Per ARM DDI 0487A.j, chapter C5.3.8 DC ZVA, Data Cache Zero by VA, > > > > "If the memory region being zeroed is any type of Device memory, this > > instruction can give an alignment fault which is prioritized in the > > same way as other alignment faults that are determined by the memory > > type." > > > > On i.MX platforms, when elf is loaded to onchip TCM area, the region > > is ioremapped, so "dc zva, dst" will trigger abort. > > > > Since memset is not strictly required, let's drop it. > > > > This would imply that we trust that the firmware doesn't expect remoteproc > to zero out the memory, which we've always done. So I don't think we can say > that it's not required. Saying an image runs on a remote core needs Linux to help zero out BSS section, this not make sense to me. My case is as following, I need to load section 7 data. I no need to let remoteproc to memset section 8/9/10/11/12, the firmware itself could handle that. Just because the memsz is larger than filesz, remoreproc must memset? Section Headers: [Nr] Name Type Addr Off Size ES Flg Lk Inf Al [ 0] NULL 00000000 000000 000000 00 0 0 0 [ 1] .interrupts PROGBITS 1ffe0000 010000 000240 00 A 0 0 4 [ 2] .resource_table PROGBITS 1ffe0240 010240 000058 00 A 0 0 1 [ 3] .text PROGBITS 1ffe02a0 0102a0 009ccc 00 AX 0 0 16 [ 4] .ARM ARM_EXIDX 1ffe9f6c 019f6c 000008 00 AL 3 0 4 [ 5] .init_array INIT_ARRAY 1ffe9f74 019f74 000004 04 WA 0 0 4 [ 6] .fini_array FINI_ARRAY 1ffe9f78 019f78 000004 04 WA 0 0 4 [ 7] .data PROGBITS 1fff9240 029240 000084 00 WA 0 0 4 [ 8] .ncache.init PROGBITS 1fff92c4 0292c4 000000 00 W 0 0 1 [ 9] .ncache NOBITS 1fff92c4 0292c4 000a80 00 WA 0 0 4 [10] .bss NOBITS 1fff9d44 0292c4 01f5c0 00 WA 0 0 4 [11] .heap NOBITS 20019304 0292c4 000404 00 WA 0 0 1 [12] .stack NOBITS 20019708 0292c4 000400 00 WA 0 0 1 > > > Signed-off-by: Peng Fan <peng.fan@xxxxxxx> > > --- > > drivers/remoteproc/remoteproc_elf_loader.c | 7 ++----- > > 1 file changed, 2 insertions(+), 5 deletions(-) > > > > diff --git a/drivers/remoteproc/remoteproc_elf_loader.c > > b/drivers/remoteproc/remoteproc_elf_loader.c > > index 16e2c496fd45..cc50fe70d50c 100644 > > --- a/drivers/remoteproc/remoteproc_elf_loader.c > > +++ b/drivers/remoteproc/remoteproc_elf_loader.c > > @@ -238,14 +238,11 @@ int rproc_elf_load_segments(struct rproc *rproc, > const struct firmware *fw) > > memcpy(ptr, elf_data + offset, filesz); > > > > /* > > - * Zero out remaining memory for this segment. > > + * No need zero out remaining memory for this segment. > > * > > * This isn't strictly required since dma_alloc_coherent already > > - * did this for us. albeit harmless, we may consider removing > > - * this. > > + * did this for us. > > In the case of recovery this comment is wrong, we do not > dma_alloc_coherent() the carveout during a recovery. Isn't the it the firmware's job to memset the region? > > And in your case you ioremapped existing TCM, so it's never true. > > > */ > > - if (memsz > filesz) > > - memset(ptr + filesz, 0, memsz - filesz); > > So I think you do want to zero out this region. Question is how we do it... I have contacted our M4 owners, we no need clear it from Linux side. We also support booting m4 before booting Linux, at that case, Linux has noting to do with memset. It is just I try loading m4 image with Linux, and met the issue that memset trigger abort. Thanks, Peng. > > Regards, > Bjorn > > > } > > > > if (ret == 0) > > -- > > 2.16.4 > >
