linux-kernel - Re: [PATCH 5/6] ARM: add low level debug uart for rk1108

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Message-ID: <56bcae77-3aed-c183-5e9f-3581cc187a7d@rock-chips.com>
Date:   Fri, 4 Nov 2016 15:58:35 +0800
From:   Andy Yan <andy.yan@...k-chips.com>
To:     Heiko Stuebner <heiko@...ech.de>
Cc:     mturquette@...libre.com, linux-rockchip@...ts.infradead.org,
        linux@...linux.org.uk, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 5/6] ARM: add low level debug uart for rk1108

Hi Heiko:


On 2016年11月04日 15:36, Heiko Stuebner wrote:
> Am Donnerstag, 3. November 2016, 20:42:21 CET schrieb Andy Yan:
>> RK1108 UARTs are Synopsis DesignWare 8250 compatible.
>> Only with different register addresses.
>>
>> Signed-off-by: Andy Yan <andy.yan@...k-chips.com>
>> ---
>>
>>   arch/arm/Kconfig.debug | 30 ++++++++++++++++++++++++++++++
>>   1 file changed, 30 insertions(+)
>>
>> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
>> index d83f7c3..408540f 100644
>> --- a/arch/arm/Kconfig.debug
>> +++ b/arch/arm/Kconfig.debug
>> @@ -776,6 +776,30 @@ choice
>>   		  their output to the standard serial port on the RealView
>>   		  PB1176 platform.
>>
>> +	config DEBUG_RK1108_UART0
>> +		bool "Kernel low-level debugging messages via Rockchip RK1108 UART0"
>> +		depends on ARCH_ROCKCHIP
>> +		select DEBUG_UART_8250
>> +		help
>> +		  Say Y here if you want kernel low-level debugging support
>> +                  on Rockchip RK1108 based platforms.
>> +
>> +	config DEBUG_RK1108_UART1
>> +		bool "Kernel low-level debugging messages via Rockchip RK1108 UART1"
>> +		depends on ARCH_ROCKCHIP
>> +		select DEBUG_UART_8250
>> +		help
>> +		  Say Y here if you want kernel low-level debugging support
>> +		  on Rockchip RK1108 based platforms.
>> +
>> +	config DEBUG_RK1108_UART2
>> +		bool "Kernel low-level debugging messages via Rockchip RK1108 UART2"
>> +		depends on ARCH_ROCKCHIP
>> +		select DEBUG_UART_8250
>> +		help
>> +		  Say Y here if you want kernel low-level debugging support
>> +		  on Rockchip RK1108 based platforms.
>> +
> are you sure, you need all 3 of them?
>
> I.e. most Rockchip SoCs so far had one uart somewhat designated as debug uart.
> Most likely due to it not having rts/cts and being used in reference
> schematics, but no one ever used another uart than uart2 on previous socs. So
> ideally we could check and only add uarts we actually need for now. More can
> be added later anyway once boards try to use them.
>
>
> Heiko
>

     Actually, I have two boards on my hand, one uses uart0 as debug 
port and the another uses uart2, so I add all of them here.

    I have a question here, I not very clear how to get the 
DEBUG_UART_VIRT value here,  I now set the value I got from uart driver 
and it works , is there some rule or  method to calculate this 
DEBUG_UART_VIRT value on different platform?
>