[U-Boot-Users] PXA255 code in start.S

[Amit Kumar]

Hello J.
        Where are you? You promised to have a look.
I can't remove the "disclaimer". Sorry for this.

Regards
Amit Kumar

-----Original Message-----
From: Jean-Christophe PLAGNIOL-VILLARD [mailto:plagnioj at jcrosoft.com]
Sent: Friday, May 16, 2008 2:41 PM
To: Amit Kumar
Cc: u-boot-users at lists.sourceforge.net; Yadvinder Singh Mann
Subject: Re: [U-Boot-Users] PXA255 code in start.S

On 12:14 Fri 16 May     , Amit Kumar wrote:
>
>
>    Hello,
>
>                Kindly refer code at path     UBOOT / u-boot / cpu / pxa /
>    start.S
>
>
>
>    Code:
>
>                .macro      irq_save_user_regs
>
>          sub   sp, sp, #S_FRAME_SIZE
>
>          stmia sp, {r0 - r12}                /* Calling r0-r12      */
>
>          add   r8, sp, #S_PC
>
>          stmdb r8, {sp, lr}^                 /* Calling SP, LR      */
>
>          str   lr, [r8, #0]                  /* Save calling PC           */
>
>          mrs   r6, spsr
>
>          str   r6, [r8, #4]                  /* Save CPSR                 */
>
>          str   r0, [r8, #8]                  /* Save OLD_R0               */
>
>          mov   r0, sp
>
>          .endm
>
>
>
>    Why there is need to save R0? If we refer ARM architecture (section what
>    all happens when interrupt comes) there is no need to save R0.
>
>
>
>    Moreover, there is no need of writing such big piece of code it can be
>    replaced with below given four liner code:
>
>
>
>          Sub   lr, lr, #4
>
>                Stmfd    sp! , {r0-r12, lr}
>
>                MRS     r1, spsr
>
>                Stmfd    sp! , {r1}
>
>
>
>    Similarly we can write small code for restore of stack
>
>                 .macro     irq_restore_user_regs
>
>                             Ldmfd  sp! , {r1}
>
>                            MSR         cpsr_c ,  R1
>                            ldmfd    sp!,  {r0-r12, pc}^
>
>                 .endm
>
>
>
>    Can anybody clarify?
I'll take a look, I'm currently cleaning the board init

Please do NOT post as HTML
>
>
>
>    Regards
>
>    Amit Kumar
>
Please remove this to

Best Regards,
J.

**************** CAUTION - Disclaimer *****************
This e-mail contains PRIVILEGED AND CONFIDENTIAL INFORMATION intended solely for the use of the addressee(s). If you are not the intended recipient, please notify the sender by e-mail and delete the original message. Further, you are not to copy, disclose, or distribute this e-mail or its contents to any other person and any such actions are unlawful. This e-mail may contain viruses. Infosys has taken every reasonable precaution to minimize this risk, but is not liable for any damage you may sustain as a result of any virus in this e-mail. You should carry out your own virus checks before opening the e-mail or attachment. Infosys reserves the right to monitor and review the content of all messages sent to or from this e-mail address. Messages sent to or from this e-mail address may be stored on the Infosys e-mail system.
***INFOSYS******** End of Disclaimer ********INFOSYS***