From: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
To: Ingo Molnar <mingo@kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
x86@kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 4/6] x86/boot: Assume MMIO if serial base address supplied via earlyprintk
Date: Tue, 16 Jan 2018 12:55:04 +0200 [thread overview]
Message-ID: <1516100104.7000.1001.camel@linux.intel.com> (raw)
In-Reply-To: <20180116031342.bxczth3ylbzdvk2r@gmail.com>
On Tue, 2018-01-16 at 04:13 +0100, Ingo Molnar wrote:
> * Andy Shevchenko <andriy.shevchenko@linux.intel.com> wrote:
>
> > If user supplied serial base address via kernel command line and
> > value
> > is higher than IO space limit (64k boundary), assume for now that
> > MMIO
> > byte access is required.
> >
> > Later we might expand or modify this if needed.
>
> Is this a standard pattern for serial code configuration values?
I didn't get what you meant under "standard" here.
IO space limit comes from generic io.h header and AFAIU is a hardware
limitation (outN (%dx), ...; inX (%dx); dx is 16 bit register).
Using mmio8 out of the IO space is dictated by the (modern) x86
platforms with non-standard (okay, high speed) UART location in address
space.
--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy
next prev parent reply other threads:[~2018-01-16 10:56 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-14 14:32 [PATCH v1 1/6] x86/boot: Convert early_serial_base to unsigned long Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 2/6] x86/boot: Introduce helpers for serial I/O Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 3/6] x86/boot: Add MMIO byte accessors Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 4/6] x86/boot: Assume MMIO if serial base address supplied via earlyprintk Andy Shevchenko
2018-01-16 3:13 ` Ingo Molnar
2018-01-16 10:55 ` Andy Shevchenko [this message]
2018-01-16 15:55 ` Ingo Molnar
2018-05-03 10:45 ` Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 5/6] x86/boot: Allow longer parameter list for earlyprintk Andy Shevchenko
2018-01-16 3:11 ` Ingo Molnar
2018-01-16 10:57 ` Andy Shevchenko
2018-01-16 15:51 ` Ingo Molnar
2018-05-03 11:48 ` Andy Shevchenko
2018-01-14 14:32 ` [PATCH v1 6/6] x86/boot: Support nocfg parameter " Andy Shevchenko
2018-01-16 3:12 ` Ingo Molnar
2018-01-16 11:00 ` Andy Shevchenko
2018-01-16 15:53 ` Ingo Molnar
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