Re: [RFC PATCH v6 1/6] riscv: mm: dma-noncoherent: Switch using function pointers for cache management

[Conor Dooley]

On Fri, Jan 06, 2023 at 11:31:33PM +0100, Arnd Bergmann wrote:
> On Fri, Jan 6, 2023, at 19:55, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > +struct riscv_cache_ops zicbom_cmo_ops = {
> > +	.clean_range = &zicbom_cmo_clean_range,
> > +	.inv_range = &zicbom_cmo_inval_range,
> > +	.flush_range = &zicbom_cmo_flush_range,
> > +};
> > +#else
> > +struct riscv_cache_ops zicbom_cmo_ops = {
> > +	.clean_range = NULL,
> > +	.inv_range = NULL,
> > +	.flush_range = NULL,
> > +	.riscv_dma_noncoherent_cmo_ops = NULL,
> > +};
> > +#endif
> > +EXPORT_SYMBOL(zicbom_cmo_ops);
> 
> Same here: If the ZICBOM ISA is disabled, nothing should
> reference zicbom_cmo_ops.

> Also, since ZICBOM is a standard
> extension, I think it makes sense to always have it enabled,
> at least whenever noncoherent DMA is supported, that way
> it can be the default that gets used in the absence of any
> nonstandard cache controller.

While I think of it, this is not possible as Zicbom requires toolchain
support whereas the alternative methods for non-coherent DMA do not.

Thanks,
Conor.

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