linux-kernel - Re: [PATCH v2 03/11] mm: ioremap: allow ARCH to have its own ioremap definition

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Date:   Tue, 23 Aug 2022 10:42:44 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Christoph Hellwig <hch@...radead.org>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        akpm@...ux-foundation.org, agordeev@...ux.ibm.com,
        wangkefeng.wang@...wei.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 03/11] mm: ioremap: allow ARCH to have its own ioremap
 definition

On 08/20/22 at 11:57pm, Christoph Hellwig wrote:
> On Sat, Aug 20, 2022 at 08:31:17AM +0800, Baoquan He wrote:
> > Architectures like xtensa, arc, can be converted to GENERIC_IOREMAP,
> > to take standard ioremap_prot() and ioremap_xxx() way. But they have
> > ARCH specific handling for ioremap() method, than standard ioremap()
> > method.
> 
> Do they?
> 
> For arc, the arc_uncached_addr_space case can be easily handled by
> arch_ioremap, and the xtensa case looks very similar to that.

I am worried it will impact ioremap_prot(). Arc has selected
HAVE_IOREMAP_PROT in Kconfig. Putting arc_uncached_addr_space() calling
into arch_ioremap() will change ioremap_prot(), right?

And I have the same about xtensa. You can see ioremap() and
ioremap_cache() will return different value since they take
XCHAL_KIO_BYPASS_VADDR and XCHAL_KIO_CACHED_VADDR differently. I haven't
figured out a way to handle them in arch_ioremap() differently.

static inline void __iomem *ioremap(unsigned long offset, unsigned long size)
{
        if (offset >= XCHAL_KIO_PADDR
            && offset - XCHAL_KIO_PADDR < XCHAL_KIO_SIZE)
                return (void*)(offset-XCHAL_KIO_PADDR+XCHAL_KIO_BYPASS_VADDR);
        else
                return xtensa_ioremap_nocache(offset, size);
}

static inline void __iomem *ioremap_cache(unsigned long offset,
                unsigned long size)
{
        if (offset >= XCHAL_KIO_PADDR
            && offset - XCHAL_KIO_PADDR < XCHAL_KIO_SIZE)
                return (void*)(offset-XCHAL_KIO_PADDR+XCHAL_KIO_CACHED_VADDR);
        else
                return xtensa_ioremap_cache(offset, size);
}

> 
> I'd really like to kill off arch definitions of ioremap going
> forward, as they should just be a special case of ioremap_prot
> by definition.