[U-Boot] [PATCH] dm: core: Add platform specific bus translation function

[Stefan Roese]

Hi Simon,

On 27.11.2015 19:36, Simon Glass wrote:
> On 27 November 2015 at 02:22, Stefan Roese <sr at denx.de> wrote:
>> This patch adds the additional platform_translate_address() call to
>> dev_get_addr(). A weak default with a 1-to-1 translation is also
>> provided. Platforms that need a special address translation can
>> overwrite this function.
>>
>> Here the explanation, why this is needed for MVEBU:
>>
>> When using DM with DT address translation, this does not work
>> with the standard fdt_translate_address() function on MVEBU
>> in SPL. Since the DT translates to the 0xf100.0000 base
>> address for the internal registers. But SPL still has the
>> registers mapped to the 0xd000.0000 (SOC_REGS_PHY_BASE)
>> address that is used by the BootROM. This is because SPL
>> may return to the BootROM for boot continuation (e.g. UART
>> xmodem boot mode).
>>
>> Signed-off-by: Stefan Roese <sr at denx.de>
>> Cc: Simon Glass <sjg at chromium.org>
>> Cc: Luka Perkov <luka.perkov at sartura.hr>
>> Cc: Dirk Eibach <dirk.eibach at gdsys.cc>
>> ---
>>   drivers/core/device.c | 36 +++++++++++++++++++++++++-----------
>>   1 file changed, 25 insertions(+), 11 deletions(-)
> 
> I wonder if there is a way to handle this with device tree? I would
> very much like to avoid adding weak functions and other types of
> hooks.

I've thought about this also for quite a bit. But couldn't come
up with a "better", less intrusive implementation for this
problem yet. 

> Are you saying that there are two values for 'ranges', one in
> SPL and one for U-Boot proper?

You can think of it as 2 values for "ranges", yes. Basically
its a difference in the upper 8 bits of all addresses of the
internal registers (e.g. UART, SDRAM controller...).

The BootROM starts with 0xd000.0000 and SPL also needs to
use this value. As SPL returns back into the BootROM in
some cases. And Linux (and other OS'es) expect 0xf100.0000
as base address. So the main U-Boot reconfigured the base
address to this value quite early.

> What actually triggers the change?

This is no change. Its just, that now SPL has added DM and DTS
support. Before this SPL-DM support this was handled by
something like this:

#if defined(CONFIG_SPL_BUILD)
#define SOC_REGS_PHY_BASE       0xd0000000
#else
#define SOC_REGS_PHY_BASE       0xf1000000
#endif
#define MVEBU_REGISTER(x)       (SOC_REGS_PHY_BASE + x)
#define MVEBU_SDRAM_SCRATCH     (MVEBU_REGISTER(0x01504))
#define MVEBU_L2_CACHE_BASE     (MVEBU_REGISTER(0x08000))
...

And now (nearly) all addresses are taken from the DT. And the
SPL vs. U-Boot proper base address difference needs to get
handled otherwise - here in the DT.
 
> One option would be to have a ranges-spl property, or similar.

Hmmm. you mean to add these "ranges-spl" properties additionally
to the normal "ranges" properties? I would really like to not
change the "ranges" in the dts files. As especially in the
MVEBU cases (Armada XP / 38x etc), the occurrences are very
high. And this would result in quite a big difference to the
"mainline Linux dts" version.

I could also add this functionality via a new Kconfig option.
Like this:

+	if (CONFIG_IS_ENABLED(PLATFORM_TRANSLATE_ADDRESS)) {
+		addr = platform_translate_address((void *)gd->fdt_blob,
+						  dev->of_offset, addr);
+	}

So no weak default would be needed. Just let me know if you
would prefer it this way. And I'll send a v2 using this
approach.

Thanks,
Stefan