Re: [PATCH] [RFC] ARM: shmobile: Add early debugging support using SCIF(A)

From: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] [RFC] ARM: shmobile: Add early debugging support using SCIF(A)
Date: Fri, 03 Oct 2014 10:19:47 +0000	[thread overview]
Message-ID: <542E7843.8090703@renesas.com> (raw)
In-Reply-To: <CAMuHMdWvYWrZBhFz7aZgV3b7S0r8OsQdPN4DBCB2+crY+Bqq=A@mail.gmail.com>

Hi Geert,

On 10/3/2014 4:21 PM, Geert Uytterhoeven wrote:
> Hi Khiem-san,
> 
> On Fri, Oct 3, 2014 at 2:04 AM, Khiem Nguyen
> <khiem.nguyen.xt@renesas.com> wrote:
>> On 10/3/2014 4:02 AM, Geert Uytterhoeven wrote:
>>> Add serial port debug macros for the SCIF(A) serial ports.
>>> This includes all shmobile SoCs, except for EMEV2.
>>>
>>> On SoCs using the legacy machine_desc.map_io(), an identity mapping of
>>> the SCIF(A) registers must be set up in .map_io(). On all but r8a7779
>>> this was already done.
>>>
>>> On other SoCs, debug_ll_io_init() maps the SCIF(A) registers to a fixed
>>> virtual address. 0xfdxxxxxx was chosen, as it should lie below
>>> VMALLOC_END = 0xff000000, and must not conflict with the 2 MiB reserved
>>> region at PCI_IO_VIRT_BASE = 0xfee00000.
>>>
>>> This was derived from the r8a7790 version by Laurent Pinchart.
>>>
>>> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
>>> ---
>>> Tested on r8a7791/koelsch and r8a7740/armadillo.
>>> Testing on other platforms would be highly appreciated.
>>
>> Uhm..., I have tried to test your patch with devel branch/renesas repo.
>> 1. CONFIG_DEBUG_SCIF is enabled in shmobile_defconfig.
>> 2. *Need to configure* CONFIG_DEBUG_UART_PHYS for lager/koelsch
>> since 0xe6c50000 (for ARCH_R8A7740) will be selected by default.
> 
> DEBUG_LL is meant for low-level debugging, and may not work well
> if multiple platforms/SoCs are enabled.
> If your kernel only has support for r8a7790/r8a7791, the default value
> of CONFIG_DEBUG_UART_PHYS should be OK.
> Else, ... well, you already noticed you can still change the address
> when configuring.
> 
>> Diff of config changed:
>> -# CONFIG_DEBUG_LL is not set
>> -CONFIG_DEBUG_LL_INCLUDE="mach/debug-macro.S"
>> +CONFIG_DEBUG_LL=y
>> +CONFIG_DEBUG_SCIF=y
>> +# CONFIG_DEBUG_ICEDCC is not set
>> +# CONFIG_DEBUG_SEMIHOSTING is not set
>> +# CONFIG_DEBUG_LL_UART_8250 is not set
>> +# CONFIG_DEBUG_LL_UART_PL01X is not set
>> +CONFIG_DEBUG_LL_INCLUDE="debug/scif.S"
>>  # CONFIG_DEBUG_UART_PL01X is not set
>>  # CONFIG_DEBUG_UART_8250 is not set
>> +CONFIG_DEBUG_UART_PHYS=0xe6e60000
>> +CONFIG_DEBUG_UNCOMPRESS=y
>>  CONFIG_UNCOMPRESS_INCLUDE="debug/uncompress.h"
>> +# CONFIG_EARLY_PRINTK is not set
>>  # CONFIG_PID_IN_CONTEXTIDR is not set
>>
>> 3. Boot up in lager/koelsch, kernel log output
>> to "booting the kernel" then ... nothing else.
>>
>> Starting kernel ...
>>
>> Uncompressing Linux... done, booting the kernel.
>>
>> Could you let me know your test procedure ?
> 
> Does enable CONFIG_EARLY_PRINTK help?

For multi-platform defconfig, it does not help.

However, I have also tried with legacy defconfig (lager_defconfig),
kernel boot is OK.

As legacy defconfig will become deprecated in near future,
I think this patch should support multi-platform defconfig.

> Thanks for testing!
No problem. 

> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 

-- 
Best regards,
KHIEM Nguyen