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Message-ID: <1497308756.2897.4.camel@kernel.crashing.org>
Subject: Re: [PATCH] drivers/misc: add Aspeed LPC snoop driver
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Rick Altherr <raltherr@google.com>, Arnd Bergmann <arnd@arndb.de>
Cc: Greg KH <gregkh@linuxfoundation.org>, OpenBMC Maillist
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Date: Tue, 13 Jun 2017 09:05:56 +1000
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On Tue, 2017-06-13 at 09:04 +1000, Benjamin Herrenschmidt wrote:
> On Fri, 2017-06-09 at 15:16 -0700, Rick Altherr wrote:
> > I've only seen the Aspeed eSPI hardware.  It implements demux of the
> > eSPI channels in the hardware and provides separate DMA descriptors
> > for each.  It looks nothing like LPC at any level.
> 
> Sort of... it does have a kind of memory mapped IO channel which
> *could* be aliased to the LPC IO space though afaik, Aspeed just
> aliases it to their internal bus which is a recipe for disaster when it
> comes to security, so one should just disable it.
> 
> It's unfortunate, I don't see how you can access things like the legacy
> UART, RTC etc... via eSPI. It looks like yet another crackpot invented
> for SMM BIOS to get in the way and emulate everything. Yuck.

That said I may just not be understanding the spec completely ... I
noticed in the SuperIO bits in the aspeed doc that there are fixed
addresses for some devices on eSPI so ... including the UART.

Ben.