From: Darren Hart <dvhart@linux.intel.com>
To: Tomoya MORINAGA <tomoya.rohm@gmail.com>
Cc: Alan Cox <alan@linux.intel.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org,
qi.wang@intel.com, yong.y.wang@intel.com, joel.clark@intel.com,
kok.howg.ewe@intel.com, feng.tang@intel.com
Subject: Re: [PATCH] pch_uart: Change default UART clock setting 192MHz
Date: Tue, 21 Feb 2012 16:20:52 -0800 [thread overview]
Message-ID: <4F4434E4.7040703@linux.intel.com> (raw)
In-Reply-To: <CANKRQnjMAVBf2wn01eFD1CKTgtWyhzk2_epz-YprZp3eS1wmMg@mail.gmail.com>
On 02/21/2012 03:43 PM, Tomoya MORINAGA wrote:
> 2012年2月22日1:07 Darren Hart <dvhart@linux.intel.com>:
>> When does the phub driver update the clock registers?
>
> I've already posted pch_phub patch for 192MHz setting.
> You can see the patch form below.
Yes, I applied the patch. The problem seems to be this:
DVHART: parse_options (8250_early.c)
DVHART: pch_console_setup
DVHART: pch_console_setup
DVHART: pch_phub_probe: set CLKCFG UART to 192MHz
As you can see, the pch_phub_probe happens much too late.
I can get it to work with a boot command line like this:
earlycon=uart8250,io,0x2050,115200n8 console=ttyPCH1,115200n8
And hacking all the BASE_BAUD references to be 48000000
(my current hardware sets the clock to 48MHz in firmware).
This gets things working until pch_phub gets around to setting
the CLKCFG register for the UART clock.
I'd prefer to not have to use the earlycon parameter/code,
but we need a way for the pch_uart to understand the difference
between early boot and post-phub setup. Can we read the CLKCFG
register in pch_console_setup to dynamically configure the
port->uartclk? (not sure that's even the right place to do it).
--
Darren
>>> Signed-off-by: Tomoya MORINAGA <tomoya.rohm@gmail.com>
>>> ---
>>> Related patch is
>>> http://marc.info/?l=linux-kernel&m=132979974907774&w=2
>
> ---
> ROHM Co., Ltd.
> tomoya
--
Darren Hart
Intel Open Source Technology Center
Yocto Project - Linux Kernel
next prev parent reply other threads:[~2012-02-22 0:21 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-02-21 4:55 [PATCH] pch_uart: Change default UART clock setting 192MHz Tomoya MORINAGA
2012-02-21 16:07 ` Darren Hart
2012-02-21 23:43 ` Tomoya MORINAGA
2012-02-22 0:20 ` Darren Hart [this message]
2012-02-22 2:28 ` Tomoya MORINAGA
2012-02-21 22:07 ` Darren Hart
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