From: Alan Cox <alan@linux.intel.com>
To: Simon Kagstrom <simon.kagstrom@netinsight.net>
Cc: x86@kernel.org, linux-serial@vger.kernel.org,
linux-kernel@vger.kernel.org, mingo@redhat.com,
tglx@linutronix.de, akpm@linux-foundation.org, hpa@zytor.com
Subject: Re: [PATCH 1/2]: serial8250: Use native_io_delay on the x86
Date: Wed, 17 Mar 2010 13:01:59 +0000 [thread overview]
Message-ID: <20100317130159.23d1103f@linux.intel.com> (raw)
In-Reply-To: <20100317133050.54851ff8@marrow.netinsight.se>
On Wed, 17 Mar 2010 13:30:50 +0100
Simon Kagstrom <simon.kagstrom@netinsight.net> wrote:
> Port 0x80 is not safe to use on all x86 boards (see
> arch/x86/kernel/io_delay.c), so use native_io_delay instead.
>
> Signed-off-by: Simon Kagstrom <simon.kagstrom@netinsight.net>
native_io_delay() won't work if the system is being run with no delays.
The I/O cycle isn't for the delay but to force the bus signals. So in
various modes (paravirt, udelay, no delay) the native_io_delay won't
actually do what is required.
I'm actually surprised you hit this path and if anything the right fix
is to avoid hitting this kind of probing in the first place.
next prev parent reply other threads:[~2010-03-17 13:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-03-17 12:28 [PATCH 0/2]: x86: Honor IO_DELAY IO port settings Simon Kagstrom
2010-03-17 12:30 ` [PATCH 1/2]: serial8250: Use native_io_delay on the x86 Simon Kagstrom
2010-03-17 13:01 ` Alan Cox [this message]
2010-03-17 14:09 ` Simon Kagstrom
2010-03-17 18:25 ` H. Peter Anvin
2010-03-17 18:36 ` Alan Cox
2010-03-17 18:43 ` H. Peter Anvin
2010-03-17 12:30 ` [PATCH 2/2]: x86 real mode: Set delay port according to kernel config Simon Kagstrom
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