booting linux from u-boot - help!
I used smc1 because i was unable to get ppcboot running with smc2. our smc1 is at 9600.
with the cache, i've disabled MSR_DR in head_8xx.S which then seems to get to start_here fine. but inserting the same code just before early_init doesn't seem to work...
the assembly I'm using is :
lis r25, 0xaaaa ori r25, r25, 0xaaaa lis r26, 0x8100 ori r26,r26,0x0000 stw r25, 0(r26)
where r25 is the pattern I want to write into address 0x81000000. I've used r25 and r26 because I can't see them being used anywhere in the code... I'm not sure how do do it otherwise (i.e. restoring the original register values)
any other ideas would be muchly appreciated,
My Hong Vuong
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Murray Jensen <[email protected]> 12/17/02 04:24pm >>>
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Thanks for the prompt response.
My pleasure.
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The board I'm working with does not utilise SDRAM, rather SRAM -
Samsung
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K1S321615M, which does not utilise burst access - our ORx has Burst Inhibit turned on - it does not support burst accesses. This
shouldn't
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pose a problem then, should it?
No you are correct, you simply won't do burst transfers on the bus which
means it can't be the problem.
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We have CPU6 turned off as we're using an MPC860T Rev.D.4.
OK
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Switching
the Copyback on and off seem to have no effect.
OK
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also, for the console, we have it set at SMC1, standard/generic serial...
SMC1 - therefore no modem control (this was going to be my next guess).
By the way, don't try to set the baud rate too high - it won't work on and SMC. A nice easy 9600 is good to use.
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i'm unclear as to what you mean by:
you must have a virtual memory mapping set up once the mmu is turned
on
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- the
head.Sfile sets one up for the IMMR and the first 8M of RAM
until
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the kernel takes over.
Do you mean that BRx and ORx need to be set up again? (btw, i'm a
newbie
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at this stuff)
No, a virtual memory mapping in the MMU. Linux takes care of this stuff, but
if you are going to be poking values into a hardware device, you need to set
up a virtual to physical address mapping and use the virtual address when the
MMU is turned on, and the physical address when it is turned off. The mapping
also needs to be non-cached.
For example, something like:
volatile phys_addr_t phys_addr = (phys_addr_t)0xXXXXXXXX; volatile void *virt_addr; volatile led_struct *led_ptr; virt_addr = ioremap(phys_addr, size); /* if MMU is off */ led_ptr = (led_struct *)phys_addr; led_ptr->... /* if MMU is on */ led_ptr = (led_struct *)virt_addr; led_ptr->...
Don't take this literally - its just quick notes to give you an idea. Note the
BRx/ORx stuff sets the "physical" address of devices, while the MMU mappings
set the "virtual" address (you don't need a mapping to access the IMMRs
- this
is done for you). Also, most places in Linux have the MMU on, except for
certain routines in the startup, and the exception handlers (in assembly).
Cheers!
Murray...
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Murray Jensen, CSIRO Manufacturing & Infra. Tech. Phone: +61 3 9662 7763 Locked Bag No. 9, Preston, Vic, 3072, Australia. Fax: +61 3 9662 7853 Internet: Murray.Jensen at csiro.au Hymod project: http://www.msa.cmst.csiro.au/projects/Hymod/ To the extent permitted by law, CSIRO does not represent, warrant and/or guarantee that the integrity of this communication has been maintained or that the communication is free of errors, virus, interception or interference. The information contained in this e-mail may be confidential or privileged. Any unauthorised use or disclosure is prohibited. If you have received this e-mail in error, please delete it immediately and notify Murray Jensen on +61 3 9662 7763. Thank you.
Quoted 1 line · In message <[email protected]> you wrote:
I used smc1 because i was unable to get ppcboot running with smc2. our
This is something you should investigate. U-Boot is working fine on all MC and SCC ports. If it doesn't work for you this means there is some problem on your board and/or with your configuration. Ignoring such problems in the early phases whiletrying to go on and "make some progress" might seem to be useful for some demonstration with upper management, but will have to be paied for double and triple later, when you run into the same problem again without knowing and expecting it. -- Just my $ 0.02. [I must live with a very primitive mind - I tend to solve problems one by one, step by step. But then, this is working not too bad for me ;-) ]
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where r25 is the pattern I want to write into address
0x81000000. I've
As Murray already pointed out: under Linux you cannot simply write to any physical address you like. Linux sets up a virtual address mapping, and each part of your physical address space you want to access must be explicitely mapped into this virtual memory.
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any other ideas would be muchly appreciated,
Well, standard recommendation applies again: get yourself a BDI2000.
Best regards,
Wolfgang Denk
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Software Engineering: Embedded and Realtime Systems, Embedded Linux Phone: (+49)-8142-4596-87 Fax: (+49)-8142-4596-88 Email: wd at denx.de On our campus the UNIX system has proved to be not only an effective software tool, but an agent of technical and social change within the University. - John Lions (U. of Toronto (?))