linux-kernel - Re: [PATCH] ARM: bcm2835: override the HW UART periphid

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Message-ID: <519C22CB.5040009@wwwdotorg.org>
Date:	Tue, 21 May 2013 19:43:39 -0600
From:	Stephen Warren <swarren@...dotorg.org>
To:	Jongsung Kim <neidhard.kim@....com>
CC:	linux@....linux.org.uk, gregkh@...uxfoundation.org, jslaby@...e.cz,
	linux-serial@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ARM: bcm2835: override the HW UART periphid

On 05/21/2013 10:34 AM, Stephen Warren wrote:
> On 05/21/2013 12:02 AM, Jongsung Kim wrote:
>> Stephen Warren reported the recent commit 78506f2 (add support for
>> extended FIFO-size of PL011-r1p5) breaks the serial port on the
>> BCM2835 ARM SoC.
>>
>> A UART compatible with the ARM PL011-r1p5 should have 32-deep FIFOs.
>> The BCM2835 UART just looks like an ARM PL011-r1p5, but has 16-deep
>> FIFOs just like PL011-r1p4 or earlier revisions. As a workaround for
>> this compatibility issue, this patch overrides the HW UART periphid
>> register values with the actually compatible UART periphid 0x00241011
>> (r1p3 or r1p4).
>>
>> Reported-by: Stephen Warren <swarren@...dotorg.org>
>> Signed-off-by: Jongsung Kim <neidhard.kim@....com>
> 
> I know this will work, because I tried out the same thing last week.
> 
> However, I'm not convinced that it's the correct approach. What other
> changes exist between r1p4 and r1p5; can you check in the TRM?

Looking at the TRM, it seems this is really the only change, according
to the changelog in the documentation (although it's a little difficult
to tell since the document seems to have a bunch of changes that
presumably don't affect behaviour). So, faking the periphid seems OK.

Acked-by: Stephen Warren <swarren@...dotorg.org>

Let's apply for 3.10.
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