Message-ID: <519AD82A.6090809@wwwdotorg.org>
Date: Mon, 20 May 2013 20:12:58 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
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To: Jongsung Kim <neidhard.kim@lge.com>
CC: "'Russell King'" <linux@arm.linux.org.uk>,
        "'Greg Kroah-Hartman'" <gregkh@linuxfoundation.org>, jslaby@suse.cz,
        linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-rpi-kernel@lists.infradead.org,
        linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] ARM: PL011: add support for extended FIFO-size of PL011-r1p5
References: <007301ce375e$bcf6d6b0$36e48410$@lge.com> <5191D200.3040604@wwwdotorg.org> <01fd01ce5072$d6b9fcd0$842df670$@lge.com> <5192A692.4010700@wwwdotorg.org> <022d01ce5107$8bc668e0$a3533aa0$@lge.com> <5193164E.6050400@wwwdotorg.org> <007001ce55c4$139f96e0$3adec4a0$@lge.com>
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On 05/20/2013 07:39 PM, Jongsung Kim wrote:
> Jongsung Kim <neidhard.kim@lge.com> :
>> Stephen Warren <swarren@wwwdotorg.org> :
>>>> All r1p5 have 32-byte FIFO depth and it's not configurable. From the 
>>>> PL011
>>>> TRM:
>>>>
>>>> r1p4-r1p5	Contains the following differences in functionality:
>>>> 		* The receive and transmit FIFOs are increased to a depth of
> 32.
>>>> 		* The Revision field in the UARTPeriphID2 Register on page
> 3-24
>>>> 		  bits [7:4] now reads back as 0x3.
>>>
>>> Well, that certainly isn't true in practice. I think we should revert 
>>> this commit until we can determine what the problem is.
>>
>> I asked to the ARM support about this. Waiting for reply..
> 
> ARM support said they doesn't have information about BCM2835 UART. Does
> anyone have a communication channel to Broadcom? It takes time for me to
> get contact point to Broadcom.. (I'm trying)
> 
> However, ARM support also said:
> 
> "If the Broadcom part definitely has 16-deep FIFOs, it cannot be based
> on a PL011 r1p5, so I might guess that Broadcom have just referenced
> the latest version of the documentation on our website, but have actually
> implemented an earlier version."

This all seems rather academic. Irrespective of what the cause of the
problem is, the commit actively breaks a previously working
configuration. I still believe we should revert it first, then find out
exactly what's going on later. Should I sent the revert commit?

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