[FSL P50x0] Xorg always restarts again and again after the the PowerPC updates 5.13-1

[Christian Zigotzky]

On 14 May 2021 at 00:58am, Nicholas Piggin wrote:
> Excerpts from Christian Zigotzky's message of May 14, 2021 6:20 am:
>> On 13 May 2021 at 07:00pm, Christophe Leroy wrote:
>>> Ah yes, I remember this problem.
>>>
>>> Can you select CONFIG_VIRT_CPU_ACCOUNTING_GEN in your configuration ?
>>>
>>> Otherwise, I can try to fix the branch.
>>>
>>> Christophe
>> I selected this. After that it compiles.
>>
>> 1. git bisect good - Xorg restarts again and again
>>       Output: [f9aa0ac1e9e82b60401ad567bdabc30598325bc1] Revert
>> "powerpc/64e/interrupt: use new interrupt return"
>> 2. git bisect good - Xorg restarts again and again
>>       Output: [cd6d259a14704741bf0cd1dcadb84c0de22d7f77] Revert
>> "powerpc/64e/interrupt: always save nvgprs on interrupt"
>> 3. git bisect bad - Xorg works
>>       Output: [9bfa20ef2ae54d3b9088dfbcde4ef97062cf5ef2] Revert
>> "powerpc/interrupt: update common interrupt code for"
>> 4. git bisect good - Xorg restarts again and again
>>       Output:
>>
>> cd6d259a14704741bf0cd1dcadb84c0de22d7f77 is the first bad commit
>> commit cd6d259a14704741bf0cd1dcadb84c0de22d7f77
>> Author: Christophe Leroy <christophe.leroy at csgroup.eu>
>> Date:   Thu May 13 09:52:06 2021 +0000
>>
>>       Revert "powerpc/64e/interrupt: always save nvgprs on interrupt"
>>
>>       This reverts commit 4228b2c3d20e9f80b847f809c38e6cf82864fa50.
>>
>> :040000 040000 156542c857ad72776b69bb67b2f244afeeb7abd3
>> 92ea86ed097fce16238b0c2f2b343473894e4e8e M    arch
> Thank you both very much for chasing this down.
>
> I think I see the problem, it's clobbering r14 and r15 for some
> interrupts. Something like this is required, I'll give it more
> review and testing though.
>
> Thanks,
> Nick
>
> ---
> diff --git a/arch/powerpc/kernel/exceptions-64e.S b/arch/powerpc/kernel/exceptions-64e.S
> index 7c3654b0d0f4..b91ef04f1ce2 100644
> --- a/arch/powerpc/kernel/exceptions-64e.S
> +++ b/arch/powerpc/kernel/exceptions-64e.S
> @@ -535,6 +535,10 @@ __end_interrupts:
>   				PROLOG_ADDITION_2REGS)
>   	mfspr	r14,SPRN_DEAR
>   	mfspr	r15,SPRN_ESR
> +	std	r14,_DAR(r1)
> +	std	r15,_DSISR(r1)
> +	ld	r14,PACA_EXGEN+EX_R14(r13)
> +	ld	r15,PACA_EXGEN+EX_R15(r13)
>   	EXCEPTION_COMMON(0x300)
>   	b	storage_fault_common
>   
> @@ -544,6 +548,10 @@ __end_interrupts:
>   				PROLOG_ADDITION_2REGS)
>   	li	r15,0
>   	mr	r14,r10
> +	std	r14,_DAR(r1)
> +	std	r15,_DSISR(r1)
> +	ld	r14,PACA_EXGEN+EX_R14(r13)
> +	ld	r15,PACA_EXGEN+EX_R15(r13)
>   	EXCEPTION_COMMON(0x400)
>   	b	storage_fault_common
>   
> @@ -557,6 +565,10 @@ __end_interrupts:
>   				PROLOG_ADDITION_2REGS)
>   	mfspr	r14,SPRN_DEAR
>   	mfspr	r15,SPRN_ESR
> +	std	r14,_DAR(r1)
> +	std	r15,_DSISR(r1)
> +	ld	r14,PACA_EXGEN+EX_R14(r13)
> +	ld	r15,PACA_EXGEN+EX_R15(r13)
>   	EXCEPTION_COMMON(0x600)
>   	b	alignment_more	/* no room, go out of line */
>   
> @@ -565,10 +577,10 @@ __end_interrupts:
>   	NORMAL_EXCEPTION_PROLOG(0x700, BOOKE_INTERRUPT_PROGRAM,
>   				PROLOG_ADDITION_1REG)
>   	mfspr	r14,SPRN_ESR
> -	EXCEPTION_COMMON(0x700)
>   	std	r14,_DSISR(r1)
> -	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	ld	r14,PACA_EXGEN+EX_R14(r13)
> +	EXCEPTION_COMMON(0x700)
> +	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	bl	program_check_exception
>   	REST_NVGPRS(r1)
>   	b	interrupt_return
> @@ -725,11 +737,11 @@ END_FTR_SECTION_IFSET(CPU_FTR_ALTIVEC)
>   	 * normal exception
>   	 */
>   	mfspr	r14,SPRN_DBSR
> -	EXCEPTION_COMMON_CRIT(0xd00)
>   	std	r14,_DSISR(r1)
> -	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	ld	r14,PACA_EXCRIT+EX_R14(r13)
>   	ld	r15,PACA_EXCRIT+EX_R15(r13)
> +	EXCEPTION_COMMON_CRIT(0xd00)
> +	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	bl	DebugException
>   	REST_NVGPRS(r1)
>   	b	interrupt_return
> @@ -796,11 +808,11 @@ kernel_dbg_exc:
>   	 * normal exception
>   	 */
>   	mfspr	r14,SPRN_DBSR
> -	EXCEPTION_COMMON_DBG(0xd08)
>   	std	r14,_DSISR(r1)
> -	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	ld	r14,PACA_EXDBG+EX_R14(r13)
>   	ld	r15,PACA_EXDBG+EX_R15(r13)
> +	EXCEPTION_COMMON_DBG(0xd08)
> +	addi	r3,r1,STACK_FRAME_OVERHEAD
>   	bl	DebugException
>   	REST_NVGPRS(r1)
>   	b	interrupt_return
> @@ -931,11 +943,7 @@ masked_interrupt_book3e_0x2c0:
>    * original values stashed away in the PACA
>    */
>   storage_fault_common:
> -	std	r14,_DAR(r1)
> -	std	r15,_DSISR(r1)
>   	addi	r3,r1,STACK_FRAME_OVERHEAD
> -	ld	r14,PACA_EXGEN+EX_R14(r13)
> -	ld	r15,PACA_EXGEN+EX_R15(r13)
>   	bl	do_page_fault
>   	b	interrupt_return
>   
> @@ -944,11 +952,7 @@ storage_fault_common:
>    * continues here.
>    */
>   alignment_more:
> -	std	r14,_DAR(r1)
> -	std	r15,_DSISR(r1)
>   	addi	r3,r1,STACK_FRAME_OVERHEAD
> -	ld	r14,PACA_EXGEN+EX_R14(r13)
> -	ld	r15,PACA_EXGEN+EX_R15(r13)
>   	bl	alignment_exception
>   	REST_NVGPRS(r1)
>   	b	interrupt_return
>
>
Hi Nicholas,

I compiled the RC1 with your patch today and Xorg works without any 
problems.

Many thanks! It was a long way.

Cheers,
Christian