[U-Boot] [PATCH 0/29] dm: Introduce device tree support in SPL (for Rockchip)

[Michael Trimarchi]

Hi

On Apr 10, 2015 7:38 PM, "Simon Glass" <sjg at chromium.org> wrote:
>
> Hi,
>
> On 27 February 2015 at 22:06, Simon Glass <sjg at chromium.org> wrote:
> > With driver model SPL support in place the remaining driver difference
> > between U-Boot proper and SPL is that SPL does not support device tree.
> > This series adds this support, using a Rockchip board as an example.
> >

Glad to test on my firefly. Can you please give some basic test to flash on
eMmc e/o on SDcard?

Michael

> > One problem with device tree is that U-Boot has no way of dropping
features
> > it does not need or use. For SPL this problem needs to be solved and
this
> > series uses the preprocessor for this. The 45KB Firefly device tree
reduces
> > to 693 bytes when unused material is removed. A better solution might
> > involve the 'fdtgrep' tool but this has not made it into the device tree
> > compiler as yet.
> >
> > This series includes some changes aimed at reduce code size in SPL,
> > including:
> > - dropping alias sequence support (the aliases node) since many boards
just
> >     use a single UART in SPL
> > - adding a smaller panic() function that does not support
printf()-format
> >     strings
> > - removing device unbind code which will never be used in SPL
> >
> > Overall the resulting SPL binary is 8829 bytes with my Linaro 4.8.2
compiler,
> > including the device tree, using Thumb-2. Of this:
> >
> > 1768 bytes is driver model core code
> > 1556 bytes is device tree code
> > 693 bytes is the device tree itself
> > 4756 is other code, including serial drivers, rodata and data
> >
> > The last figure includes rodata incorrectly added by the tool chain [1].
> > With a bug-fixed gcc 4.9.2 the total size is 6893 bytes including device
> > tree.
> >
> > Approximately 750 bytes is used for strings and driver data (root device
> > and serial) associated with driver model and device tree. This adds up
an
> > overhead of around 4750 bytes for driver model and device tree,
including
> > the code, rodata and device tree itself.
> >
> > It should therefore be possible to use driver model and device tree in
> > SPL for board that have enough SRAM. Clearly 4KB is impossible without
> > further work (perhaps removing some error strings). I suspect 8KB would
> > be tricky, allowing only 3KB for stack and other code. But 16KB should
> > work OK.
> >
> > SRAM sizes for recent SoCs I am aware of are:
> >
> > Rockchip RK3288:     96KB
> > Tegra 124:           128KB
> > Samsung Exynos 5420: 384KB
> >
> > The Rockchip Firefly was chosen for this work since it is a fairly
recent
> > board and is readily available. Rockchip engineers have been actively
> > upstreaming code to Linux in the past year and there is a very
> > full-featured U-Boot available. But it is invisible to most U-Boot
> > people - mainline Rockchip support seems well overdue. This series does
> > not make a serious start on that, since it only prints a message in SPL
> > and then hangs, but additional work should get it booting to a prompt.
> >
> > [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=54303
>
> I've held off pushing this into u-boot-dm/next since it is RFC and the
> device tree part needs work. But I'm thinking of respinning it to
> apply it within the upcoming merge window, or at least the core
> patches.
>
> Does anyone have comments at this stage?
>
> Regards,
> Simon
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