linux-kernel - Re: [PATCH] EFI: Do not use __pa() to get the physical address of an ioremapped memory range

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Date:	Tue, 13 Sep 2011 16:48:47 +0800
From:	huang ying <huang.ying.caritas@...il.com>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Zhang Rui <rui.zhang@...el.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg59@...f.ucam.org>, x86@...nel.org
Subject: Re: [PATCH] EFI: Do not use __pa() to get the physical address of an
 ioremapped memory range

On Mon, Sep 12, 2011 at 10:52 PM, Matt Fleming <matt@...sole-pimps.org> wrote:
> On Fri, 2011-09-02 at 13:12 +0800, huang ying wrote:
>> On Thu, Sep 1, 2011 at 8:28 PM, Matt Fleming <matt@...sole-pimps.org> wrote:
>> >
>> > Hmm.. does anyone know why we ioremap_cache() the memory on
>> > CONFIG_X86_32 instead of ioremap_nocache()? In the case of
>> > EFI_MEMORY_MAPPED_IO the memory really needs to be uncached. Then if
>> > we've ioremap'd the memory we should skip set_memory_uc() altogether,
>> > no?
>>
>> Because whether the mapping should be cached is determined by md->attr
>> instead of md->type.  And besides UC, we may add WC, etc support.
>
> Confused.
>
> The CONFIG_X86_64 version of efi_ioremap() looks like this,
>
> void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
>                                 u32 type)
> {
>        unsigned long last_map_pfn;
>
>        if (type == EFI_MEMORY_MAPPED_IO)
>                return ioremap(phys_addr, size);
>
> Which uses md->type to figure out if we should call ioremap(), which on
> x86 is #define'd to ioremap_nocache(). CONFIG_X86_32 doesn't do this,
> but it looks to me like it should.

I don't think this type based solution is the perfect one.

Best Regards,
Huang Ying
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