From patchwork Thu Jun 10 18:37:53 2021
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Date: Thu, 10 Jun 2021 20:37:53 +0200 (CEST)
From: "Maciej W. Rozycki" <macro@orcam.me.uk>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>
cc: linux-serial@vger.kernel.org, linux-mips@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH 0/2] serial, Malta: Fixes to make the CBUS UART work
 big-endian
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Hi,

 Earlier this year I noticed the CBUS UART, a discrete TI16C550C part 
wired directly to the system controller's device bus and supposed to come 
up as ttyS2 in addition to ttyS0 and ttyS1 ports from a Super I/O device 
behind the PCI southbridge, is not recognised with my MIPS Malta board 
booting big-endian.

 I used to use it just fine, many many years ago, although in the board's 
little-endian configuration only, and then with a local patch to get it 
supported with Linux 2.4.x, which I didn't get to submitting however due 
to the turn of events back then.  Support was then added by someone else 
with 2.6.23.

 I got to the bottom of the problem now and as it turns out we have two 
long-standing bugs causing it, one in generic 8250 code and another in 
Malta platform code, and this has never worked in the big-endian mode.  
Evidently, this has never been verified, and I guess this is because back 
in the MIPS UK days we usually ran the boards in the little-endian mode.

 This pair of patches addresses these bugs individually.  See the 
respective change descriptions for details.

 Please apply.

  Maciej