Commit e7bc8557 authored by Paul Burton's avatar Paul Burton Committed by Ralf Baechle
Browse files

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: default avatarPaul Burton <paul.burton@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16202/


Signed-off-by: default avatarRalf Baechle <ralf@linux-mips.org>
parent fa7a3b4a

arch/mips/include/asm/cpu-features.h

+41 −0
Original line number Diff line number Diff line
@@ -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

 */

arch/mips/include/asm/cpu.h

+4 −0
Original line number Diff line number Diff line
@@ -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

arch/mips/kernel/cpu-probe.c

+11 −0
Original line number Diff line number Diff line
@@ -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)

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