[PATCH 1/2] lib: utils: Implement "64bit-mmio" property parsing

[Guo Ren]

On Sat, Apr 17, 2021 at 7:45 PM Jessica Clarke <jrtc27 at jrtc27.com> wrote:
>
> On 17 Apr 2021, at 12:41, Jessica Clarke <jrtc27 at jrtc27.com> wrote:
> >
> > On 13 Apr 2021, at 04:44, guoren at kernel.org wrote:
> >>
> >> From: Guo Ren <guoren at linux.alibaba.com>
> >>
> >> Figure out CLINT has_64bit_mmio from DT node and using antonym for
> >> compatibility.
> >>
> >> Signed-off-by: Guo Ren <guoren at linux.alibaba.com>
> >> Cc: Anup Patel <anup.patel at wdc.com>
> >> Cc: Xiang W <wxjstz at 126.com>
> >> ---
> >> lib/utils/fdt/fdt_helper.c | 3 ++-
> >> 1 file changed, 2 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/lib/utils/fdt/fdt_helper.c b/lib/utils/fdt/fdt_helper.c
> >> index bf19ff9..909de01 100644
> >> --- a/lib/utils/fdt/fdt_helper.c
> >> +++ b/lib/utils/fdt/fdt_helper.c
> >> @@ -442,8 +442,9 @@ int fdt_parse_clint_node(void *fdt, int nodeoffset, bool for_timer,
> >>      if (clint->hart_count < count)
> >>              clint->hart_count = count;
> >>
> >> -    /* TODO: We should figure-out CLINT has_64bit_mmio from DT node */
> >>      clint->has_64bit_mmio = TRUE;
> >> +    if (fdt_getprop(fdt, nodeoffset, "clint,has-no-64bit-mmio", &count))
> >
> > I do not see this specified in clint.yaml.
>
> Also, the RISC-V privileged is very clear:
>
> > For RV64, naturally aligned 64-bit memory accesses to the mtime and mtimecmp
> > registers are atomic.
>
> So I would say your CLINT violates the spec and thus should not claim to be a
> RISC-V or SiFive-compatible CLINT.
>
> Jess
>

Normal Linux use csr_read(CSR_TIME), and C9xx wouldn't support
M-mode&MMU-less Linux. So the only sbi_set_timer would be affected.

Because mmio-32bit is perfect with RV32, it wouldn't cause problems in
the RV64 linux mmu s-mode system.


--
Best Regards
 Guo Ren

ML: https://lore.kernel.org/linux-csky/