Re: [RESEND][PATCH] ARM: debug: add support for Palmchip 16550-like UART

["Måns Rullgård" <mans@mansr.com>]

Mason <slash.tmp@free.fr> writes:

> On 27/10/2015 13:57, Mans Rullgard wrote:
>
>> Some SoCs have a Palmchip UART with a non-standard register layout.
>> This allows the debug console to work with these.
>> 
>> Signed-off-by: Mans Rullgard <mans@mansr.com>
>> ---
>>  arch/arm/Kconfig.debug        |  8 ++++++++
>>  arch/arm/include/debug/8250.S | 12 ++++++++++++
>>  2 files changed, 20 insertions(+)
>> 
>> diff --git a/arch/arm/Kconfig.debug b/arch/arm/Kconfig.debug
>> index 0cfd7f9..9039fff 100644
>> --- a/arch/arm/Kconfig.debug
>> +++ b/arch/arm/Kconfig.debug
>> @@ -1597,6 +1597,14 @@ config DEBUG_UART_8250_WORD
>>  		DEBUG_BCM_KONA_UART || DEBUG_RK32_UART2 || \
>>  		DEBUG_BRCMSTB_UART
>>  
>> +config DEBUG_UART_8250_PALMCHIP
>> +	bool "8250 UART is Palmchip variant"
>> +	depends on DEBUG_LL_UART_8250 || DEBUG_UART_8250
>
> I am 100% clueless about the UART sequence in Linux.
>
> There's earlyprintk, the boot console (polled?), the "full-blown"
> console (with IRQs)...
>
> If I want earlyprintk, I have to enable DEBUG_LL (?) so I'll have
> DEBUG_LL_UART_8250, right? There's no way to pick DEBUG_UART_8250
> in menuconfig, is there?
>
> So I picked the following options:
>
> CONFIG_DEBUG_LL=y
> # CONFIG_DEBUG_ICEDCC is not set
> # CONFIG_DEBUG_SEMIHOSTING is not set
> CONFIG_DEBUG_LL_UART_8250=y
> # CONFIG_DEBUG_LL_UART_PL01X is not set
> CONFIG_DEBUG_LL_INCLUDE="debug/8250.S"
> # CONFIG_DEBUG_UART_8250 is not set
> # CONFIG_DEBUG_UART_BCM63XX is not set
> CONFIG_DEBUG_UART_PHYS=0x10700
> CONFIG_DEBUG_UART_VIRT=0xf0010700
> CONFIG_DEBUG_UART_8250_SHIFT=2
> CONFIG_DEBUG_UART_8250_WORD=y
> CONFIG_DEBUG_UART_8250_PALMCHIP=y
> # CONFIG_DEBUG_UART_8250_FLOW_CONTROL is not set
> CONFIG_DEBUG_UNCOMPRESS=y
> CONFIG_UNCOMPRESS_INCLUDE="debug/uncompress.h"
> CONFIG_EARLY_PRINTK=y

Those are the settings I use.

> I suppose I have to provide DEBUG_UART_PHYS because it needs
> the address before it can parse the DT? But how am I supposed
> to know the virtual address? Isn't that from iomap(UART_PHYS)?

The decompression code and early setup don't have that luxury.

> 'make' wouldn't let me proceed unless I gave something...
>
> Then I have to add earlyprintk to my boot command line, right?
> Do I need to specify more than that?

Just earlyprintk without any parameters works.

-- 
Måns Rullgård
mans@mansr.com