From: Linus Walleij <linus.walleij@linaro.org>
To: Vitaly Wool <vitalywool@gmail.com>
Cc: Grant Likely <grant.likely@secretlab.ca>,
spi-devel-general@lists.sourceforge.net,
Lee Jones <lee.jones@linaro.org>,
linux-arm-kernel@lists.infradead.org,
Magnus Templing <magnus.templing@stericsson.com>
Subject: Re: [PATCH 1/2] spi/pl022: timeout on polled transfer v2
Date: Thu, 19 May 2011 20:06:32 +0200 [thread overview]
Message-ID: <BANLkTikR7A1Y4sumjZXS5ou3ex7PJOi1CA@mail.gmail.com> (raw)
In-Reply-To: <BANLkTi=COt5Te4bF1M30A+R4Vqnz=kWiJA@mail.gmail.com>
2011/5/19 Vitaly Wool <vitalywool@gmail.com>:
> On Thu, May 19, 2011 at 7:36 PM, Linus Walleij <linus.walleij@linaro.org> wrote:
>>>
>>> just out of curiosity: is it a busy wait? Looks like it is...
>>
>> Yep that's the polling mode part. IRQ and DMA mode should
>> be the norm I guess.
>>
>> Magnus: do you have a specific use case for this thing?
>
> Well, adding cpu_relax() somewhere in the loop might be not a bad idea...
OK sent a patch for it, and Grant applied it within something like
30 seconds :-)
I think on ARM that just boils down to a barrier() so it
basically injects air in the pipeline when busywaiting, I never
understood what that is good for, but it's a good marker anyway.
Linus Walleij
prev parent reply other threads:[~2011-05-19 18:06 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-05-19 16:05 [PATCH 1/2] spi/pl022: timeout on polled transfer v2 Linus Walleij
2011-05-19 16:55 ` Grant Likely
[not found] ` <1305821134-26147-1-git-send-email-linus.walleij-0IS4wlFg1OjSUeElwK9/Pw@public.gmane.org>
2011-05-19 17:04 ` Vitaly Wool
2011-05-19 17:36 ` Linus Walleij
2011-05-19 17:40 ` Vitaly Wool
2011-05-19 18:06 ` Linus Walleij [this message]
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