[U-Boot] ATAGS for Tegra, Sunxi, etc.

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Masahiro Yamada]

+ To: U-Boot ML

I forgot to send this to ML.




2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
> Hi,
>
> I noticed some well-maintained new SoC families still
> define CONFIG_CMDLINE_TAG.
>
>
> For example,
>
> include/configs/tegra-common.h
>
>   #define CONFIG_CMDLINE_TAG              /* enable passing of ATAGs */
>
>
>
> include/configs/sunxi-common.h
>
>  #define CONFIG_SETUP_MEMORY_TAGS
>  #define CONFIG_CMDLINE_TAG
>  #define CONFIG_INITRD_TAG
>  #define CONFIG_SERIAL_TAG
>
>
>
> Do they still use ATAGS, not device tree?
>
>
>
> --
> Best Regards
> Masahiro Yamada



-- 
Best Regards
Masahiro Yamada

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Ian Campbell]

On Thu, 2015-12-17 at 07:40 +0100, Karsten Merker wrote:
> On Thu, Dec 17, 2015 at 01:59:57PM +0900, Masahiro Yamada wrote:
> > 2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.c
> > om>:
> > > Hi,
> > > 
> > > I noticed some well-maintained new SoC families still
> > > define CONFIG_CMDLINE_TAG.
> > > 
> > > 
> > > For example,
> [...]
> > > include/configs/sunxi-common.h
> > > 
> > > ?#define CONFIG_SETUP_MEMORY_TAGS
> > > ?#define CONFIG_CMDLINE_TAG
> > > ?#define CONFIG_INITRD_TAG
> > > ?#define CONFIG_SERIAL_TAG
> 
> > > Do they still use ATAGS, not device tree?
> 
> Sunxi uses devicetree for mainline kernels, but AFAIK ATAG
> support is necessary to enable booting legacy vendor kernels.
> There is still new sunxi-based hardware sold today that comes
> with legacy 3.4-based kernels.

That legacy kernel is FEX (allwinners own description blob) based, I don't
know to what extent that involves ATAGs in some way though.

There are also people who use the 3.4 based fork from linux-sunxi.org, but
I don't know if that is DT or ATAGS or FEX.

A dependency on CONFIG_OLD_SUNXI_KERNEL_COMPAT might be an option depending
on what the kernels need, Hans probably knows better than I do.

Ian.

> CCing Hans de Goede and Ian Cambell (sunxi maintainers).

> 
> Regards,
> Karsten

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Hans de Goede]

Hi,

On 17-12-15 10:21, Ian Campbell wrote:
> On Thu, 2015-12-17 at 07:40 +0100, Karsten Merker wrote:
>> On Thu, Dec 17, 2015 at 01:59:57PM +0900, Masahiro Yamada wrote:
>>> 2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.c
>>> om>:
>>>> Hi,
>>>>
>>>> I noticed some well-maintained new SoC families still
>>>> define CONFIG_CMDLINE_TAG.
>>>>
>>>>
>>>> For example,
>> [...]
>>>> include/configs/sunxi-common.h
>>>>
>>>>   #define CONFIG_SETUP_MEMORY_TAGS
>>>>   #define CONFIG_CMDLINE_TAG
>>>>   #define CONFIG_INITRD_TAG
>>>>   #define CONFIG_SERIAL_TAG
>>
>>>> Do they still use ATAGS, not device tree?
>>
>> Sunxi uses devicetree for mainline kernels, but AFAIK ATAG
>> support is necessary to enable booting legacy vendor kernels.
>> There is still new sunxi-based hardware sold today that comes
>> with legacy 3.4-based kernels.
>
> That legacy kernel is FEX (allwinners own description blob) based, I don't
> know to what extent that involves ATAGs in some way though.
>
> There are also people who use the 3.4 based fork from linux-sunxi.org, but
> I don't know if that is DT or ATAGS or FEX.
>
> A dependency on CONFIG_OLD_SUNXI_KERNEL_COMPAT might be an option depending
> on what the kernels need, Hans probably knows better than I do.

The 3.4 based kernels use both ATAGS for things like memory size, and fex
for other hw config info.

I'm not in favor of wrapping things in CONFIG_OLD_SUNXI_KERNEL_COMPAT, because
recent 3.4 based kernels can boot without that, and I believe that removing
the ATAG support will break this, without really buying us much.

Regards,

Hans

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Tom Rini]

On Thu, Dec 17, 2015 at 10:26:07AM +0100, Hans de Goede wrote:
> Hi,
> 
> On 17-12-15 10:21, Ian Campbell wrote:
> >On Thu, 2015-12-17 at 07:40 +0100, Karsten Merker wrote:
> >>On Thu, Dec 17, 2015 at 01:59:57PM +0900, Masahiro Yamada wrote:
> >>>2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.c
> >>>om>:
> >>>>Hi,
> >>>>
> >>>>I noticed some well-maintained new SoC families still
> >>>>define CONFIG_CMDLINE_TAG.
> >>>>
> >>>>
> >>>>For example,
> >>[...]
> >>>>include/configs/sunxi-common.h
> >>>>
> >>>>  #define CONFIG_SETUP_MEMORY_TAGS
> >>>>  #define CONFIG_CMDLINE_TAG
> >>>>  #define CONFIG_INITRD_TAG
> >>>>  #define CONFIG_SERIAL_TAG
> >>
> >>>>Do they still use ATAGS, not device tree?
> >>
> >>Sunxi uses devicetree for mainline kernels, but AFAIK ATAG
> >>support is necessary to enable booting legacy vendor kernels.
> >>There is still new sunxi-based hardware sold today that comes
> >>with legacy 3.4-based kernels.
> >
> >That legacy kernel is FEX (allwinners own description blob) based, I don't
> >know to what extent that involves ATAGs in some way though.
> >
> >There are also people who use the 3.4 based fork from linux-sunxi.org, but
> >I don't know if that is DT or ATAGS or FEX.
> >
> >A dependency on CONFIG_OLD_SUNXI_KERNEL_COMPAT might be an option depending
> >on what the kernels need, Hans probably knows better than I do.
> 
> The 3.4 based kernels use both ATAGS for things like memory size, and fex
> for other hw config info.
> 
> I'm not in favor of wrapping things in CONFIG_OLD_SUNXI_KERNEL_COMPAT, because
> recent 3.4 based kernels can boot without that, and I believe that removing
> the ATAG support will break this, without really buying us much.

+1.  ATAG is also used iirc for some other operating systems, still.

-- 
Tom
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[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Stephen Warren]

On 12/16/2015 09:59 PM, Masahiro Yamada wrote:
> + To: U-Boot ML
>
> I forgot to send this to ML.
>
>
>
>
> 2015-12-17 13:58 GMT+09:00 Masahiro Yamada <yamada.masahiro@socionext.com>:
>> Hi,
>>
>> I noticed some well-maintained new SoC families still
>> define CONFIG_CMDLINE_TAG.
>>
>>
>> For example,
>>
>> include/configs/tegra-common.h
>>
>>    #define CONFIG_CMDLINE_TAG              /* enable passing of ATAGs */

IIRC, Tegra support in U-Boot was added in the days before DT was a 
thing, or a widespread thing at least. (Oh, happy days!) I imagine that 
the config option was simply never removed since there was no specific 
need to do so.

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Masahiro Yamada]

Hi everyone,


Thanks for explanation!
Keeping ATAGS makes sense for combination of new U-Boot and old Linux.



-- 
Best Regards
Masahiro Yamada

[U-Boot] ATAGS for Tegra, Sunxi, etc.

[Marcel Ziswiler]

On Thu, 2015-12-17 at 09:44 -0700, Stephen Warren wrote:

> IIRC, Tegra support in U-Boot was added in the days before DT was a?
> thing, or a widespread thing at least. (Oh, happy days!) I imagine
> that?
> the config option was simply never removed since there was no
> specific?
> need to do so.

Please remember that at least for T20 and T30 NVIDIA's officially
supported Linux for Tegra (L4T) is still based on the ancient Linux
kernel 3.1.10 relying on ATAGs. While Colibri T20 and Apalis/Colibri
T30 are mainline since a while there is still no solution for hardware
accelerated graphics/multimedia compatible with mainline as far as I
know. So for hardware accelerated graphics/multimedia one is pretty
much stuck with L4T requiring ATAGs!