On Thu, Jun 20, 2013 at 03:13:57PM +0400, Sergei Shtylyov wrote:
> >+#if !defined(CONFIG_CPU_CAVIUM_OCTEON)
>
> Suggesting to use if (!IS_ENABLED(CONFIG_CPU_CAVIUM_OCTEON)) to
> avoid #ifdef...
An ifdef in disguise. IS_ENABLED() gives better coverage in build tests
but that's about it, it allows more readable formatting. But that's
about it's advantages.
Never use CONFIG_CPU_* to conditionally execute code only on certain
CPU types. It's not consistently used like this everywhere but it's meant
to select optimization for a particular processor type.
For example on the Malta, a system that's notorious for supporting
particularly man processor types CONFIG_CPU_R4X00 might be set but the
actual core core be a lowly R4Kc or the latest 666Kfc MIPS64 R6 core from
hell.
CONFIG_SYS_HAS_CPU_* only expresses that a system _might_ be equipped
with a particular processor, that is support for this core should be
compiled in. An arbitrary number of CONFIG_SYS_HAS_CPU_* may be enabled.
If you really need to test for a processor at runtime, use current_cpu_type().
Typically that's done in a switch and there are plenty of example scattered
around arch/mips/mm/.
It's possible to replace the current current_cpu_type() with a platform-
specific version that looks (example for Cavium Octeon) like:
static inline int __pure current_cpu_type(void)
{
const int cpu_type = current_cpu_data.cputype;
switch (cpu_type) {
case CPU_CAVIUM_OCTEON:
case CPU_CAVIUM_OCTEON_PLUS:
case CPU_CAVIUM_OCTEON2:
break;
default:
unreachable();
}
return cpu_type;
}
Modern GCC will then notice that current_cpu_type() may only ever return
the values CPU_CAVIUM_OCTEON, CPU_CAVIUM_OCTEON_PLUS and CPU_CAVIUM_OCTEON2
and will discard all the non-Octeon code from a switch construct like this:
switch (current_cpu_type()) {
case CPU_R2000:
case CPU_R3000:
...
break;
case CPU_CAVIUM_OCTEON:
case CPU_CAVIUM_OCTEON_PLUS:
case CPU_CAVIUM_OCTEON2:
break;
}
Result: sane, clean code.
Ralf
MIPS: Fix TLBR-use hazards for R2 cores in the TLB reload handlers
MIPS R2 documents state that an execution hazard barrier is needed
after a TLBR before reading EntryLo.
Original patch by Leonid Yegoshin <Leonid.Yegoshin@xxxxxxxxxx>.
Signed-off-by: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
---
arch/mips/mm/tlbex.c | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)
diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
index bfff8fe..34c882c 100644
--- a/arch/mips/mm/tlbex.c
+++ b/arch/mips/mm/tlbex.c
@@ -1932,6 +1932,19 @@ static void __cpuinit build_r4000_tlb_load_handler(void)
uasm_i_nop(&p);
uasm_i_tlbr(&p);
+
+ switch (current_cpu_type()) {
+ default:
+ if (cpu_has_mips_r2) {
+ uasm_i_ehb(&p);
+
+ case CPU_CAVIUM_OCTEON:
+ case CPU_CAVIUM_OCTEON_PLUS:
+ case CPU_CAVIUM_OCTEON2:
+ break;
+ }
+ }
+
/* Examine entrylo 0 or 1 based on ptr. */
if (use_bbit_insns()) {
uasm_i_bbit0(&p, wr.r2, ilog2(sizeof(pte_t)), 8);
@@ -1986,6 +1999,19 @@ static void __cpuinit build_r4000_tlb_load_handler(void)
uasm_i_nop(&p);
uasm_i_tlbr(&p);
+
+ switch (current_cpu_type()) {
+ default:
+ if (cpu_has_mips_r2) {
+ uasm_i_ehb(&p);
+
+ case CPU_CAVIUM_OCTEON:
+ case CPU_CAVIUM_OCTEON_PLUS:
+ case CPU_CAVIUM_OCTEON2:
+ break;
+ }
+ }
+
/* Examine entrylo 0 or 1 based on ptr. */
if (use_bbit_insns()) {
uasm_i_bbit0(&p, wr.r2, ilog2(sizeof(pte_t)), 8);
