From: hpa@zytor.com
To: "Mehta, Sohil" <sohil.mehta@intel.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"andriy.shevchenko@linux.intel.com"
<andriy.shevchenko@linux.intel.com>,
"mingo@redhat.com" <mingo@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "mitake@dcl.info.waseda.ac.jp" <mitake@dcl.info.waseda.ac.jp>
Subject: Re: [PATCH v1] x86/io: Define readq()/writeq() to use 64-bit type
Date: Mon, 22 Jan 2018 16:46:59 -0800 [thread overview]
Message-ID: <FDFCAF1F-F4F8-4376-AD78-6208008F63DE@zytor.com> (raw)
In-Reply-To: <1516667578.153063.78.camel@intel.com>
On January 22, 2018 4:32:14 PM PST, "Mehta, Sohil" <sohil.mehta@intel.com> wrote:
>On Fri, 2018-01-19 at 16:33 +0200, Andy Shevchenko wrote:
>> Since non atomic readq() and writeq() were added some of the drivers
>> would like to use it in a manner of:
>>
>> #include <io-64-nonatomic-lo-hi.h>
>> ...
>> pr_debug("Debug value of some register: %016llx\n", readq(addr));
>>
>> However, lo_hi_readq() always returns __u64 data, while readq()
>> on x86_64 defines it as unsigned long. and thus compiler warns
>> about type mismatch, although they are both 64-bit on x86_64.
>>
>> Convert readq() and writeq() on x86 to operate on deterministic
>> 64-bit type. The most of architectures in the kernel already are
>> using
>> either unsigned long long, or u64 type for readq() / writeq().
>> This change propagates consistency in that sense.
>>
>> While this is not an issue per se, though if someone wants to address
>> it,
>> the anchor could be the commit
>>
>> 797a796a13df ("asm-generic: architecture independent readq/writeq
>> for 32bit environment")
>>
>> where non-atomic variants had been introduced.
>>
>> Note, there are only few users of above pattern and they will not be
>> affected because they do cast returned value. The actual warning has
>> been issued on not-yet-upstreamed code.
>>
>> Potentially we might get a new warnings if some 64-bit only code
>> assigns returned value to unsigned long type of variable. This is
>> assumed to be addressed on case-by-case basis.
>>
>> Reported-by: lkp <lkp@intel.com>
>> Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
>> Cc: "Mehta, Sohil" <sohil.mehta@intel.com>
>> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
>> ---
>> arch/x86/include/asm/io.h | 8 ++++----
>> 1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h
>> index 95e948627fd0..365f5ba9222b 100644
>> --- a/arch/x86/include/asm/io.h
>> +++ b/arch/x86/include/asm/io.h
>> @@ -94,10 +94,10 @@ build_mmio_write(__writel, "l", unsigned int,
>> "r", )
>>
>> #ifdef CONFIG_X86_64
>>
>> -build_mmio_read(readq, "q", unsigned long, "=r", :"memory")
>> -build_mmio_read(__readq, "q", unsigned long, "=r", )
>> -build_mmio_write(writeq, "q", unsigned long, "r", :"memory")
>> -build_mmio_write(__writeq, "q", unsigned long, "r", )
>> +build_mmio_read(readq, "q", unsigned long long, "=r", :"memory")
>> +build_mmio_read(__readq, "q", unsigned long long, "=r", )
>> +build_mmio_write(writeq, "q", unsigned long long, "r", :"memory")
>> +build_mmio_write(__writeq, "q", unsigned long long, "r", )
>>
>> #define readq_relaxed(a) __readq(a)
>> #define writeq_relaxed(v, a) __writeq(v, a)
>
>The patch works for me:
>
>Tested-by: Sohil Mehta <sohil.mehta@intel.com>
>
>Sohil
Wouldn't simply u64 make more sense?
--
Sent from my Android device with K-9 Mail. Please excuse my brevity.
next prev parent reply other threads:[~2018-01-23 0:51 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-19 14:33 [PATCH v1] x86/io: Define readq()/writeq() to use 64-bit type Andy Shevchenko
2018-01-23 0:32 ` Mehta, Sohil
2018-01-23 0:46 ` hpa [this message]
2018-01-23 8:32 ` Andy Shevchenko
2018-01-29 15:45 ` Andy Shevchenko
2018-02-13 16:58 ` [tip:x86/urgent] " tip-bot for Andy Shevchenko
2018-03-27 15:10 ` Andy Shevchenko
2018-03-31 10:19 ` Ingo Molnar
2018-03-31 10:22 ` Ingo Molnar
2018-03-31 12:06 ` Andy Shevchenko
2018-03-31 12:15 ` Andy Shevchenko
2018-03-31 18:45 ` Ingo Molnar
2018-04-02 14:55 ` Andy Shevchenko
2018-04-24 16:51 ` Andy Shevchenko
2018-03-31 12:05 ` Andy Shevchenko
2018-03-31 10:20 ` [tip:x86/platform] " tip-bot for Andy Shevchenko
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