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MIPS: Add CPU shared FTLB feature detection 

Some systems share FTLB RAMs or entries between sibling CPUs (ie.
hardware threads, or VP(E)s, within a core). These properties require
kernel handling in various places. As a start this patch introduces
cpu_has_shared_ftlb_ram & cpu_has_shared_ftlb_entries feature macros
which we set appropriately for I6400 & I6500 CPUs. Further patches will
make use of these macros as appropriate.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16202/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
This commit is contained in:
Paul Burton 2017-06-02 15:38:01 -07:00 committed by Ralf Baechle
parent fa7a3b4a72
commit e7bc855742
3 changed files with 56 additions and 0 deletions
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41
arch/mips/include/asm/cpu-features.h
View File

@ -487,6 +487,47 @@
# define cpu_has_perf (cpu_data[0].options & MIPS_CPU_PERF)
#endif
#if defined(CONFIG_SMP) && defined(__mips_isa_rev) && (__mips_isa_rev >= 6)
/*
* Some systems share FTLB RAMs between threads within a core (siblings in
* kernel parlance). This means that FTLB entries may become invalid at almost
* any point when an entry is evicted due to a sibling thread writing an entry
* to the shared FTLB RAM.
*
* This is only relevant to SMP systems, and the only systems that exhibit this
* property implement MIPSr6 or higher so we constrain support for this to
* kernels that will run on such systems.
*/
# ifndef cpu_has_shared_ftlb_ram
# define cpu_has_shared_ftlb_ram \
(current_cpu_data.options & MIPS_CPU_SHARED_FTLB_RAM)
# endif
/*
* Some systems take this a step further & share FTLB entries between siblings.
* This is implemented as TLB writes happening as usual, but if an entry
* written by a sibling exists in the shared FTLB for a translation which would
* otherwise cause a TLB refill exception then the CPU will use the entry
* written by its sibling rather than triggering a refill & writing a matching
* TLB entry for itself.
*
* This is naturally only valid if a TLB entry is known to be suitable for use
* on all siblings in a CPU, and so it only takes effect when MMIDs are in use
* rather than ASIDs or when a TLB entry is marked global.
*/
# ifndef cpu_has_shared_ftlb_entries
# define cpu_has_shared_ftlb_entries \
(current_cpu_data.options & MIPS_CPU_SHARED_FTLB_ENTRIES)
# endif
#endif /* SMP && __mips_isa_rev >= 6 */
#ifndef cpu_has_shared_ftlb_ram
# define cpu_has_shared_ftlb_ram 0
#endif
#ifndef cpu_has_shared_ftlb_entries
# define cpu_has_shared_ftlb_entries 0
#endif
/*
* Guest capabilities
*/

4
arch/mips/include/asm/cpu.h
View File

@ -418,6 +418,10 @@ enum cpu_type_enum {
#define MIPS_CPU_GUESTID MBIT_ULL(51) /* CPU uses VZ ASE GuestID feature */
#define MIPS_CPU_DRG MBIT_ULL(52) /* CPU has VZ Direct Root to Guest (DRG) */
#define MIPS_CPU_UFR MBIT_ULL(53) /* CPU supports User mode FR switching */
#define MIPS_CPU_SHARED_FTLB_RAM \
MBIT_ULL(54) /* CPU shares FTLB RAM with another */
#define MIPS_CPU_SHARED_FTLB_ENTRIES \
MBIT_ULL(55) /* CPU shares FTLB entries with another */
/*
* CPU ASE encodings

11
arch/mips/kernel/cpu-probe.c
View File

@ -1653,6 +1653,17 @@ static inline void cpu_probe_mips(struct cpuinfo_mips *c, unsigned int cpu)
decode_configs(c);
spram_config();
switch (__get_cpu_type(c->cputype)) {
case CPU_I6500:
c->options |= MIPS_CPU_SHARED_FTLB_ENTRIES;
/* fall-through */
case CPU_I6400:
c->options |= MIPS_CPU_SHARED_FTLB_RAM;
/* fall-through */
default:
break;
}
}
static inline void cpu_probe_alchemy(struct cpuinfo_mips *c, unsigned int cpu)