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To:     Arnd Bergmann <arnd@kernel.org>, Will Deacon <will@kernel.org>
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References: <20210304213902.83903-1-marcan@marcan.st>
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 <CAK8P3a0913Hs4VfHjdDY1WTAQvMzC83LJcP=9zeE0C-terfBhA@mail.gmail.com>
From:   Hector Martin <marcan@marcan.st>
Subject: Re: [RFT PATCH v3 08/27] asm-generic/io.h: Add a non-posted variant
 of ioremap()
Message-ID: <9e510158-551a-3feb-bdba-17e070f12a8e@marcan.st>
Date:   Thu, 25 Mar 2021 23:07:40 +0900
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On 25/03/2021 04.09, Arnd Bergmann wrote:
> On Wed, Mar 24, 2021 at 7:12 PM Will Deacon <will@kernel.org> wrote:
>>
>>> +/*
>>> + * ioremap_np needs an explicit architecture implementation, as it
>>> + * requests stronger semantics than regular ioremap(). Portable drivers
>>> + * should instead use one of the higher-level abstractions, like
>>> + * devm_ioremap_resource(), to choose the correct variant for any given
>>> + * device and bus. Portable drivers with a good reason to want non-posted
>>> + * write semantics should always provide an ioremap() fallback in case
>>> + * ioremap_np() is not available.
>>> + */
>>> +#ifndef ioremap_np
>>> +#define ioremap_np ioremap_np
>>> +static inline void __iomem *ioremap_np(phys_addr_t offset, size_t size)
>>> +{
>>> +     return NULL;
>>> +}
>>> +#endif
>>
>> Can we implement the generic pci_remap_cfgspace() in terms of ioremap_np()
>> if it is supported by the architecture? That way, we could avoid defining
>> both on arm64.
> 
> Good idea. It needs a fallback in case the ioremap_np() fails on most
> architectures, but that sounds easy enough.
> 
> Since pci_remap_cfgspace() only has custom implementations, it sounds like
> we can actually make the generic implementation unconditional in the end,
> but that requires adding ioremap_np() on 32-bit as well, and I would keep
> that separate from this series.

Sounds good; I'm adding a patch to adjust the generic implementation and 
remove the arm64 one in v4, and we can then complete the cleanup for 
other arches later.

-- 
Hector Martin (marcan@marcan.st)
Public Key: https://mrcn.st/pub