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

[Peter Robinson]

On Mon, Apr 2, 2018 at 3:56 AM, Simon Glass <sjg at chromium.org> wrote:
> 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.

It's a lot more work for the way most distros build u-boot, but TBH
the sooner I don't need to the better ;-)