commit 3c7c7a2fc8 ("ARC: Don't use "+l" inline asm constraint")
modified the inline assembly to setup LP_COUNT register manually and NOT
rely on gcc to do it (with the +l inline assembler contraint hint, now
being retired in the compiler)
However the fix was flawed as we didn't add LP_COUNT to asm clobber list,
meaning gcc doesn't know that LP_COUNT or zero-delay-loops are in action
in the inline asm.
This resulted in some fun - as nested ZOL loops were being generared
| mov lp_count,250000 ;16 # tmp235,
| lp .L__GCC__LP14 # <======= OUTER LOOP (gcc generated)
| .L14:
| ld r2, [r5] # MEM[(volatile u32 *)prephitmp_43], w
| dmb 1
| breq r2, -1, @.L21 #, w,,
| bbit0 r2,1,@.L13 # w,,
| ld r4,[r7] ;25 # loops_per_jiffy, loops_per_jiffy
| mpymu r3,r4,r6 #, loops_per_jiffy, tmp234
|
| mov lp_count, r3 # <====== INNER LOOP (from inline asm)
| lp 1f
| nop
| 1:
| nop_s
| .L__GCC__LP14: ; loop end, start is @.L14 #,
This caused issues with drivers relying on sane behaviour of udelay
friends.
With LP_COUNT added to clobber list, gcc doesn't generate the outer
loop in say above case.
Addresses STAR 9001146134
Reported-by: Joao Pinto <jpinto@synopsys.com>
Fixes: 3c7c7a2fc8 ("ARC: Don't use "+l" inline asm constraint")
Cc: stable@vger.kernel.org
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
36425cd670