From mboxrd@z Thu Jan 1 00:00:00 1970 From: robin.murphy@arm.com (Robin Murphy) Date: Fri, 22 Apr 2016 18:08:46 +0100 Subject: [PATCH 4/7] io-64-nonatomic: Add relaxed accessor variants In-Reply-To: <20160421161859.GK929@arm.com> References: <44173fd4e8efd27d670cadc6b30e215243a14099.1460391217.git.robin.murphy@arm.com> <20160421161859.GK929@arm.com> Message-ID: <571A5A9E.7040305@arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 21/04/16 17:18, Will Deacon wrote: > On Wed, Apr 13, 2016 at 06:13:00PM +0100, Robin Murphy wrote: >> Whilst commit 9439eb3ab9d1 ("asm-generic: io: implement relaxed >> accessor macros as conditional wrappers") makes the *_relaxed forms of >> I/O accessors universally available to drivers, in cases where writeq() >> is implemented via the io-64-nonatomic helpers, writeq_relaxed() will >> end up falling back to writel() regardless of whether writel_relaxed() >> is available (identically for s/write/read/). >> >> Add corresponding relaxed forms of the nonatomic helpers to delegate >> to the equivalent 32-bit accessors as appropriate. >> >> CC: Arnd Bergmann >> CC: Christoph Hellwig >> CC: Darren Hart >> CC: Hitoshi Mitake >> Signed-off-by: Robin Murphy >> --- >> include/linux/io-64-nonatomic-hi-lo.h | 25 +++++++++++++++++++++++++ >> include/linux/io-64-nonatomic-lo-hi.h | 25 +++++++++++++++++++++++++ >> 2 files changed, 50 insertions(+) >> >> diff --git a/include/linux/io-64-nonatomic-hi-lo.h b/include/linux/io-64-nonatomic-hi-lo.h >> index 11d7e84..1a85566 100644 >> --- a/include/linux/io-64-nonatomic-hi-lo.h >> +++ b/include/linux/io-64-nonatomic-hi-lo.h >> @@ -21,6 +21,23 @@ static inline void hi_lo_writeq(__u64 val, volatile void __iomem *addr) >> writel(val, addr); >> } >> >> +static inline __u64 hi_lo_readq_relaxed(const volatile void __iomem *addr) >> +{ >> + const volatile u32 __iomem *p = addr; >> + u32 low, high; >> + >> + high = readl_relaxed(p + 1); >> + low = readl_relaxed(p); >> + >> + return low + ((u64)high << 32); >> +} >> + >> +static inline void hi_lo_writeq_relaxed(__u64 val, volatile void __iomem *addr) >> +{ >> + writel_relaxed(val >> 32, addr + 4); >> + writel_relaxed(val, addr); >> +} > > Could we not generate the _relaxed variants with some macro magic? We _could_ - indeed I started doing that, but then decided that the obfuscation of horrible macro-templated functions wasn't worth saving a couple of hundred bytes in some code that isn't exactly difficult to maintain and has needed touching once in 4 years. If you did want to go down the macro route, I may as well also generate both lo-hi and hi-lo headers all from a single template, it'd be really clever... ;) Robin. > > Will >