Re: [PATCH 2/2] ARM: dts: meson: Adding hwrev syscon node

[Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>]

On Thursday 18 February 2016 15:27:06 Daniel Drake wrote:
> 
> Having a cbus bus node with child devices does sound like it would
> reflect this particular view of the hardware design. How would we then
> represent the hwrev registers under that?
> 

The question is still how the CBUS is structured internally.

https://github.com/endlessm/linux-meson/blob/master/arch/arm/mach-meson8b/include/mach/register.h

seems to have a good list of registers, but it's a bit hard to
read, so I reformatted it slightly and put it up at http://pastebin.com/GrzYM7Ti

In many cases, the register name prefix gives a good idea of what things
are. In particular, it seems that all registers numbers are between 0x1000
and 0x2fff, which would be offsets 0x4000 through 0xbfff.

The revisison register is in a block called ASSIST, which is mixed with two
AC3 (audio?) regions, and the only other ASSIST register that is ever
used is the ASSIST_POR_CONFIG.

The METAL_REVISION is in the middle of some apparently all unrelated registers:

#define PREG_ETH_REG0 0x2050
#define PREG_ETH_REG1 0x2051
#define PROD_TEST_REG1 0x2067
#define PROD_TEST_REG0 0x2068
#define METAL_REVISION 0x206a
#define ADC_TOP_MISC 0x206b
#define DPLL_TOP_MISC 0x206c
#define ANALOG_TOP_MISC 0x206d
#define AM_ANALOG_TOP_REG0 0x206e
#define AM_ANALOG_TOP_REG1 0x206f
#define PREG_STICKY_REG0 0x207c
#define PREG_STICKY_REG1 0x207d

This still really sounds like a mixed bag to me, which should better get represented
as a syscon node, except that there are also some more structured areas in
CBUS.

Having just the registers between METAL_REVISION and HW_REV in a syscon
is clearly wrong, as that would include the pinctrl area that already has
a driver, but would not include some other parts that want the syscon.

Maybe the best way is to make it compatible with both syscon and
simple-bus and put the other nodes underneath. That is still rather
ugly, but at least it works and can be extended.

	Arnd
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