8:36 p.m.
Feng Tang <feng.tang(a)intel.com> writes:
Hi Christophe and Michael,
On Mon, Jan 18, 2021 at 10:24:08PM +0800, Christophe Leroy wrote:
>
> Le 05/01/2021 ? 11:58, kernel test robot a 閏rit :
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
master
> > head: e71ba9452f0b5b2e8dc8aa5445198cd9214a6a62
> > commit: 8b8319b181fd9d6821703fef1228b4dcde613a16 powerpc/44x: Don't support
440 when CONFIG_PPC_47x is set
>
> I see no link with that commit. Looks like the problem has been existing for some
time.
> It exists on the commit before that one, it exists on v5.9 and it exists on v5.10
with that commit
> reverted.
Yes, this seems to be a long-standing issue, and we just double checked
this compile error.
It happend when compiling arch/powerpc/platforms/44x/fsp2.c, macro
'mfdcr' requirs an instant number as parameter, while is not met by
show_plbopb_regs(). Changing show_plbopb_regs() from function to
a macro fixes the error, as the patch below:
Thanks,
Feng
From 3bcb9638afc873d0e803aea1aad4f77bf1c2f6f6 Mon Sep 17 00:00:00 2001
From: Feng Tang <feng.tang(a)intel.com>
Date: Fri, 5 Feb 2021 16:08:43 +0800
Subject: [PATCH] powerpc/44x/fsp2: fix a compiling error regarding macro
'mdfcr'
0day's kbuild test found error:
"
CC arch/powerpc/platforms/44x/fsp2.o
{standard input}:577: Error: unsupported relocation against base
{standard input}:580: Error: unsupported relocation against base
{standard input}:583: Error: unsupported relocation against base
"
The reason is macro 'mfdcr' requirs an instant number as parameter,
which is not met by show_plbopb_regs().
It doesn't require a constant, it checks if the argument is constant:
#define mfdcr(rn) \
({unsigned int rval; \
if (__builtin_constant_p(rn) && rn < 1024) \
asm volatile("mfdcr %0," __stringify(rn) \
: "=r" (rval)); \
else if (likely(cpu_has_feature(CPU_FTR_INDEXED_DCR))) \
rval = mfdcrx(rn); \
else \
rval = __mfdcr(rn); \
rval;})
But the error you're seeing implies the compiler is choosing the first
leg of the if, even when rn == "base + x", which is surprising.
We've had cases in the past of __builtin_constant_p() returning false
for things that a human can see are constant at build time, but I've
never seen the reverse.
cheers