[U-Boot] [PATCH 05/12] aspeed/ast2500: Device Tree and bindings for some of the clocks

[Simon Glass]

Hi Maxim,

On 23 January 2017 at 10:52, Maxim Sloyko <maxims at google.com> wrote:
> On Fri, Jan 20, 2017 at 7:52 PM, Simon Glass <sjg at chromium.org> wrote:
>>
>> Hi Maxim,
>>
>> On 17 January 2017 at 16:27, Maxim Sloyko <maxims at google.com> wrote:
>> >
>> >
>> > On Sat, Jan 14, 2017 at 9:13 AM, Simon Glass <sjg at chromium.org> wrote:
>> >>
>> >> Hi Maxim,
>> >>
>> >> On 5 January 2017 at 15:20, Maxim Sloyko <maxims at google.com> wrote:
>> >> > On Wed, Jan 4, 2017 at 7:26 PM, Tom Rini <trini at konsulko.com> wrote:
>> >> >> On Wed, Jan 04, 2017 at 05:18:42PM -0800, Maxim Sloyko wrote:
>> >> >>> On Wed, Jan 4, 2017 at 12:58 PM, Tom Rini <trini at konsulko.com> wrote:
>> >> >>> > On Wed, Jan 04, 2017 at 11:46:49AM -0800, Maxim Sloyko wrote:
>> >> >>> >
>> >> >>> >> Signed-off-by: Maxim Sloyko <maxims at google.com>
>> >> >>> >> ---
>> >> >>> >>
>> >> >>> >>  arch/arm/dts/ast2500.dtsi               | 423
>> >> >>> >> ++++++++++++++++++++++++++++++++
>> >> >>> >>  include/dt-bindings/clock/ast2500-scu.h |  29 +++
>> >> >>> >>  2 files changed, 452 insertions(+)
>> >> >>> >>  create mode 100644 arch/arm/dts/ast2500.dtsi
>> >> >>> >>  create mode 100644 include/dt-bindings/clock/ast2500-scu.h
>> >> >>> >>
>> >> >>> >> diff --git a/arch/arm/dts/ast2500.dtsi b/arch/arm/dts/ast2500.dtsi
>> >> >>> >> new file mode 100644
>> >> >>> >> index 0000000000..1a2a3f7ee3
>> >> >>> >> --- /dev/null
>> >> >>> >> +++ b/arch/arm/dts/ast2500.dtsi
>> >> >>> >> @@ -0,0 +1,423 @@
>> >> >>> >> +/* This device tree is copied from
>> >> >>> >> + *
>> >> >>> >> https://github.com/openbmc/linux/blob/c5682cb/arch/arm/boot/dts/aspeed-g5.dtsi
>> >> >>> >
>> >> >>> > Is this also found in the Linux kernel or not yet?  Thanks!
>> >> >>>
>> >> >>> Yes, this is also in in main Linux kernel now, as I've found out, but
>> >> >>> actually there is a number of differences, most notably there is no
>> >> >>> pin configuration in this device tree, because there is no pinctrl
>> >> >>> driver.
>> >> >
>> >> > Actually, I take that back, I was looking at the wrong linux Linux
>> >> > kernel tree still... Only basic version of device tree has made it to
>> >> > mainline kernel, but it's enough at the moment, so I used that
>> >> > instead.
>> >> >
>> >> >>>
>> >> >>> Should I remove this reference or modify it?
>> >> >>
>> >> >> Ideally, we will take the kernel dts files and then add what we need on
>> >> >> top of that in one of CONFIG_SYS_CPU/CONFIG_SYS_SOC/CONFIG_SYS_VENDOR
>> >> >> -u-boot.dtsi files, see for example arch/arm/dts/sunxi-u-boot.dtsi or
>> >> >> arch/arm/dts/tegra124-nyan-big-u-boot.dtsi
>> >> >
>> >> > OK, so I took the device tree from the Linux kernel, (ast2500.dtsi),
>> >> > added modifications in ast2500-u-boot.dtsi and now include
>> >> > ast2500-u-boot.dtsi in ast2500-evb.dts. Let me know if I misunderstood
>> >> > you.
>> >>
>> >> There is some magic in the Makefile which automatically includes the
>> >> .dtsi if you name it correctly:
>> >>
>> >> # Try these files in order to find the U-Boot-specific .dtsi include file
>> >> u_boot_dtsi_options = $(wildcard $(dts_dir)/$(basename $(notdir
>> >> $<))-u-boot.dtsi) \
>> >> $(wildcard $(dts_dir)/$(subst $\",,$(CONFIG_SYS_SOC))-u-boot.dtsi) \
>> >> $(wildcard $(dts_dir)/$(subst $\",,$(CONFIG_SYS_CPU))-u-boot.dtsi) \
>> >> $(wildcard $(dts_dir)/$(subst $\",,$(CONFIG_SYS_VENDOR))-u-boot.dtsi) \
>> >> $(wildcard $(dts_dir)/u-boot.dtsi)
>> >>
>> >>
>> >> So you should not need to include it explicitly.
>> >
>> >
>> > Well, it looks like the only applicable for this case would be
>> > CONFIG_SYS_SOC, but it looks like this setting also affects the mach- and
>> > arch- directories used. In this case I want different aspeed SoCs to share
>> > those directories, but
>> > they will have different DTs.
>>
>> The first option is to a .dtsi derived from the .dts filename. Does that help?
>
> Hmm, probably not... if I understand that correctly.
>
> This is what I have right now:
>
> ast2500.dtsi -- device tree from the linux kernel, used by all
> ast2500-based boards.
> ast2500-u-boot.dtsi -- these are u-boot specific additions, with
> u-boot,dm-pre-reloc labels, clock specification and SDRAM driver node.
> These are still need to be shared by all ast2500-based boards.
> ast2500-evb.dts -- Eval board specific stuff, right now basically just
> chosen node with stdout-path and clock frequency specification for
> SDRAM.
>
> I don't this it would make sense to have ast2500-evb-u-boot.dtsi just
> to avoid include, because when I later create ast2500-zaius-bmc.dts or
> something like that, I would have the same problem.

Yes you may as well have your own include.

The idea is to use the same files as Linux, and put the U-Boot
additions in a separate file. But it's not critical - just a new idea
we had. Also if you can get the U-Boot additions into the upstream
Linux version then you won't need this.

Regards,
Simon