[PATCH 05/14] at91: use structure to store the current soc
plagnioj at jcrosoft.com
Thu Apr 28 19:06:52 EDT 2011
On 08:20 Fri 29 Apr , Ryan Mallon wrote:
> On 04/29/2011 02:10 AM, Jean-Christophe PLAGNIOL-VILLARD wrote:
> > On 16:04 Thu 28 Apr , Andrew Victor wrote:
> >> hi,
> >>>> If this eventually reduces code size then I think it is useful, but
> >>>> otherwise I'm not sure I see the point?
> >>> It's on purpose as the dbgu physical address is not at the same place
> >>> so read the other register really does not impact the chip but if we do it
> >>> later duting the boot or the life to the kernel it's an other story
> >>> so the split between __cpu_is and cpu_is is necessarly
> >>> all of this work is in preparation to allow multiple soc in the same kernel
> >>> that's also why I map the system controller the same way on all at91 arm9
> >> The cpu_is() or__cpu_is() perform a at91_sys_read() of one of the DBGU
> >> registers.
> >> But the address of the DBGU differs between CPUs regardless if you map
> >> the system controller the same:
> >> at572d940hf.h:#define AT91_DBGU (0xfffff200 - AT91_BASE_SYS)
> >> at91cap9.h:#define AT91_DBGU (0xffffee00 - AT91_BASE_SYS)
> >> at91rm9200.h:#define AT91_DBGU (0xfffff200 - AT91_BASE_SYS)
> >> at91sam9260.h:#define AT91_DBGU (0xfffff200 - AT91_BASE_SYS)
> >> at91sam9261.h:#define AT91_DBGU (0xfffff200 - AT91_BASE_SYS)
> >> at91sam9263.h:#define AT91_DBGU (0xffffee00 - AT91_BASE_SYS)
> >> at91sam9g45.h:#define AT91_DBGU (0xffffee00 - AT91_BASE_SYS)
> >> at91sam9rl.h:#define AT91_DBGU (0xfffff200 - AT91_BASE_SYS)
> >> So I don't see how you can "detect" the CPU without first knowing
> >> which CPU and therefore where the DBGU register is anyway.
> >> And probing different addresses for a value is not an acceptable solution.
> >> While having a single kernel image that supports AT91 processors is a
> >> good goal, the soc.h is a totally unnecessary complication.
> >> I can't think of any situation where an AT91 board.c file doesn't know
> >> what processor it has.
> >> So instead of :
> >> boardXYZ-init -> at91_initialize() --> magic-cpu-detection -->
> >> at91XX_initialize()
> >> just do:
> >> boardXYZ-init -> at91XX_initialize()
> > except there is no need to known it and board seach as the usb-926x are the
> > same nearly and do not need to known on which soc they are
> > ditto for other boards you do not need to known the soc we are on.
> > And when you work on CPU module the board is the same but not the cpu on the
> > module so detect the SOC allow to have one kernel for all and not multiple
> > machine ID for each module and board combination
> I Agree with Andrew. When can determine everything we need from the
> mach-type. For boards such as the usb-926x we have two separate
> mach-types for the 9263 and the 9260 variants. The init_machine callback
> can be separated in this case so that both of the boards initialise the
> correct cpu type.
I do work on board where is the case and I do not want to keep the limitation
and yes I'll put them mainline
And Russell will not accept I'll create 10 or 20 machine ID for board / cpu
module combinaison just because of different I do not detect the SOC type
so I'll continue to detect the soc
More information about the linux-arm-kernel