Subject: Re: [PATCH V3 1/7] remoteproc: elf: support platform specific memory hook

From: Bjorn Andersson <[email-masked]>
Date: Fri, 4 Dec 2020 18:16:57 -0600

On Fri 04 Dec 01:40 CST 2020, Peng Fan (OSS) wrote:

> From: Peng Fan <[email-masked]>
> 
> 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. And ioremap_wc()
> on i.MX not able to write correct data to TCM area.
> 
> So we need to use io helpers, and extend the elf loader to support
> platform specific memory functions.
> 
> Acked-by: Richard Zhu <[email-masked]>
> Signed-off-by: Peng Fan <[email-masked]>
> Reviewed-by: Mathieu Poirier <[email-masked]>
> ---
>  drivers/remoteproc/remoteproc_elf_loader.c | 20 ++++++++++++++++++--
>  include/linux/remoteproc.h                 |  4 ++++
>  2 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/remoteproc/remoteproc_elf_loader.c b/drivers/remoteproc/remoteproc_elf_loader.c
> index df68d87752e4..6cb71fe47261 100644
> --- a/drivers/remoteproc/remoteproc_elf_loader.c
> +++ b/drivers/remoteproc/remoteproc_elf_loader.c
> @@ -129,6 +129,22 @@ u64 rproc_elf_get_boot_addr(struct rproc *rproc, const struct firmware *fw)
>  }
>  EXPORT_SYMBOL(rproc_elf_get_boot_addr);
>  
> +static void rproc_elf_memcpy(struct rproc *rproc, void *dest, const void *src, size_t count)
> +{
> +	if (!rproc->ops->elf_memcpy)
> +		memcpy(dest, src, count);
> +
> +	rproc->ops->elf_memcpy(rproc, dest, src, count);

Looking at the current set of remoteproc drivers I get a feeling that
we'll end up with a while bunch of functions that all just wraps
memcpy_toio(). And the reason for this is that we are we're "abusing" the
carveout to carry the __iomem pointer without keeping track of it.

And this is not the only time we're supposed to use an io-accessor,
another example is rproc_copy_segment() in rproc_coredump.c

It also means that if a platform driver for some reason where to support
both ioremap and normal carveouts the elf_memcpy op would be quite
quirky.

So I would prefer if we track the knowledge about void *va being a
__iomem or not in the struct rproc_mem_entry and make rproc_da_to_va()
return this information as well.

Then instead of extending the ops we can make this simply call memcpy or
memcpy_toio() depending on this.

Regards,
Bjorn

> +}
> +
> +static void rproc_elf_memset(struct rproc *rproc, void *s, int c, size_t count)
> +{
> +	if (!rproc->ops->elf_memset)
> +		memset(s, c, count);
> +
> +	rproc->ops->elf_memset(rproc, s, c, count);
> +}
> +
>  /**
>   * rproc_elf_load_segments() - load firmware segments to memory
>   * @rproc: remote processor which will be booted using these fw segments
> @@ -214,7 +230,7 @@ int rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw)
>  
>  		/* put the segment where the remote processor expects it */
>  		if (filesz)
> -			memcpy(ptr, elf_data + offset, filesz);
> +			rproc_elf_memcpy(rproc, ptr, elf_data + offset, filesz);
>  
>  		/*
>  		 * Zero out remaining memory for this segment.
> @@ -224,7 +240,7 @@ int rproc_elf_load_segments(struct rproc *rproc, const struct firmware *fw)
>  		 * this.
>  		 */
>  		if (memsz > filesz)
> -			memset(ptr + filesz, 0, memsz - filesz);
> +			rproc_elf_memset(rproc, ptr + filesz, 0, memsz - filesz);
>  	}
>  
>  	return ret;
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index e8ac041c64d9..06c52f88a3fd 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -373,6 +373,8 @@ enum rsc_handling_status {
>   *			expects to find it
>   * @sanity_check:	sanity check the fw image
>   * @get_boot_addr:	get boot address to entry point specified in firmware
> + * @elf_memcpy:		platform specific elf loader memcpy
> + * @elf_memset:		platform specific elf loader memset
>   * @panic:	optional callback to react to system panic, core will delay
>   *		panic at least the returned number of milliseconds
>   */
> @@ -392,6 +394,8 @@ struct rproc_ops {
>  	int (*load)(struct rproc *rproc, const struct firmware *fw);
>  	int (*sanity_check)(struct rproc *rproc, const struct firmware *fw);
>  	u64 (*get_boot_addr)(struct rproc *rproc, const struct firmware *fw);
> +	void (*elf_memcpy)(struct rproc *rproc, void *dest, const void *src, size_t count);
> +	void (*elf_memset)(struct rproc *rproc, void *s, int c, size_t count);
>  	unsigned long (*panic)(struct rproc *rproc);
>  };
>  
> -- 
> 2.28.0
> 

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