Re: [microblaze-uclinux] Microblaze slices and BRAMs optimizationwith uclinux

[Claudio Lanconelli <lanconelli.claudio@xxxxxxxxx>]

John Williams wrote:

>> Can I configure the opb_timer with only one 32bit timer 
>> (C_ONE_TIMER_ONLY=1)?
>
>
> That should be fine - the kernel only uses channel 0 for the system 
> timer.
>

I tried to synthesize with C_ONE_TIMER_ONLY=1, but it saves only 40 slices.

> Also, it should be pretty simple to tweak the kernel to use the FIT 
> (fixed interval timer) rather than the programmable timer.  The FIT is 
> likely to be a lot smaller than the opb_timer
>
Yes, it should be really smaller than opb_timer, however it probably 
needs some interrupt glue logic (not sure). Furthermore I Looked at the 
sources and I find mach_gettimeoffset() in machine.c. How can I 
implement this with only the fit_timer?

>> uclinux-auto depends on the lmb_bram_controller in any ways?
>
>
> Currently rhe kernel makes no use of the LMB memory.  The LMB_MEMORY 
> parameter in the MSS file is just for completeness.  You should 
> actually be able to set that to "none" without difficulty.
>

If I set the LMB_MEMORY to "none" in mss file the generated 
auto-config.in lacks the lines

define_hex CONFIG_XILINX_LMB_START 0x00000000
define_hex CONFIG_XILINX_LMB_SIZE 0x00002000

these defines are used by the ram.ld.in

MEMORY {
    LMB  : ORIGIN = CONFIG_XILINX_LMB_START,
           LENGTH = CONFIG_XILINX_LMB_SIZE
    ERAM  : ORIGIN = CONFIG_XILINX_ERAM_START,
                LENGTH = CONFIG_XILINX_ERAM_SIZE
}

to build the linux.ld file

MEMORY {
    LMB  : ORIGIN = CONFIG_XILINX_LMB_START,
           LENGTH = CONFIG_XILINX_LMB_SIZE
    ERAM  : ORIGIN = 0x80000000 ,
                LENGTH = 0x02000000
}

So the linker complain about CONFIG_XILINX_LMB_START is not a constant.

If I set the LMB_MEMORY to "opb_bram_cntrl" in mss file the script stops 
with errors.
What is PERIPH_TYPE_OVERRIDES? May be useful for this purpose?

Cheers,
Claudio Lanconelli
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