[U-Boot] [PATCH 1/3] dm: Add migration plan for CONFIG_BLK

[Simon Glass]

Hi Peter,

On 2 April 2018 at 10:45, Peter Robinson <pbrobinson at gmail.com> wrote:
> On Mon, Apr 2, 2018 at 3:28 AM, Simon Glass <sjg at google.com> wrote:
>> Hi Andre,
>>
>> On 2 April 2018 at 09:43, André Przywara <andre.przywara at arm.com> wrote:
>>> Hi,
>>>
>>> On 01/04/18 14:19, Tom Rini wrote:
>>>> On Tue, Mar 27, 2018 at 11:34:19PM +0530, Jagan Teki wrote:
>>>>> On Mon, Sep 4, 2017 at 9:57 PM,  <sjg at google.com> wrote:
>>>>>> Hi Tom,
>>>>>>
>>>>>> On 7 August 2017 at 09:39, Tom Rini <trini at konsulko.com> wrote:
>>>>>>> On Sat, Aug 05, 2017 at 03:45:53PM -0600, Simon Glass wrote:
>>>>>>>
>>>>>>>> The CONFIG_BLK conversion involves quite invasive changes in the U-Boot
>>>>>>>> code, with #ifdefs and different code paths. We should try to move over to
>>>>>>>> this soon so we can drop the old code.
>>>>>
>>>>> I hope this will applicable to SPL too?
>>>>>
>>>>> If so, we are having SPL size issues with few Allwinner families, if
>>>>> enable SPL_DM any suggestions?
>>>>
>>>> How close, and have you looked at the u-boot-spl.map to see what you can
>>>> maybe trim?  Or areas to look at reducing in code complexity?
>>>
>>> The Boot ROM limit for all Allwinner SoCs known so far is 32KB. The A64
>>> SPL (AArch64) stands at ~31KB at the moment. Yes, we went over the map
>>> and picked most low hanging fruits already.
>>> So far we discussed several mitigations, but mostly to cover the
>>> "natural" SPL code size grow over time:
>>> 1) The AArch64 exception vectors take 1KB, plus an unnecessary ~1.6KB of
>>> padding (for a 2KB architectural alignment). Given that the vectors are
>>> used only for debugging purposes, we could scrap them entirely or
>>> construct them on the fly in some other SRAM. So would free about 2.5KB,
>>> ideally. Lowest hanging fruit so far.
>>> 2) We can compile the SPL in AArch32 mode, which can use the Thumb2
>>> encoding. This reduces the size significantly, to about 20KB. The
>>> disadvantage is using a second cross-compiler or even a additional
>>> cross-compiler for native builds, complicating the build process.
>>> I maintain a branch for enabling FEL booting here [1], which provides
>>> two _defconfigs (one 32-bit for SPL, one 64-bit for U-Boot proper).
>>> There are no technical disadvantages in running the SPL in 32-bit, so
>>> this is mostly a build issue.
>>
>> FYI 32-bit tegra compiles SPL with ARMv4T and U-Boot proper with
>> ARMv7. It should be fairly easy to do,
>
> ARMv4 and ARMv7 are both 32 bit though, as opposed to 32 and 64 bit in
> the case of Allwinner A64

Yes, but that is just a matter of compiler or compiler flags. My point
was we should be able to use different build for each without too much
work.

Regards,
Simon