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From: Krzysztof Halasa <khc@pm.waw.pl>
To: Sascha Hauer <s.hauer@pengutronix.de>
Cc: barebox@lists.infradead.org
Subject: Re: [PATCH] Cosmetic: fix endianness convertions in read[wlq]().
Date: Sun, 06 May 2012 22:08:48 +0200	[thread overview]
Message-ID: <m3397dysvj.fsf@intrepid.localdomain> (raw)
In-Reply-To: <20120506173507.GV4141@pengutronix.de> (Sascha Hauer's message of "Sun, 6 May 2012 19:35:07 +0200")

Sascha Hauer <s.hauer@pengutronix.de> writes:

>> -#define readw(addr) __le16_to_cpu(__raw_readw(addr))
>> -#define readl(addr) __le32_to_cpu(__raw_readl(addr))
>> +#define readw(addr) __cpu_to_le16(__raw_readw(addr))
>> +#define readl(addr) __cpu_to_le32(__raw_readl(addr))
>
> This seems wrong. readw/l are supposed to do little endian reads and that
> is exactly what the code you remove does: It reads in cpu native
> endianess and interprets that as a little endian word which is then
> converted into cpu native endian word.
> (Also the code is copied from the kernel which makes me quite confident
> that it's correct)

Well... That's right. I forgot the PCI on ARM is set in order-preserving
mode. This means that while the peripherals (u32) are accessed simply
with __raw_readl(), on PCI bus __raw_readl() yields wrong-endian value
(le32 instead of u32). I wonder how it passes sparse.
-- 
Krzysztof Halasa

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      reply	other threads:[~2012-05-06 20:12 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-05 21:36 Krzysztof Halasa
2012-05-06 17:35 ` Sascha Hauer
2012-05-06 20:08   ` Krzysztof Halasa [this message]

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