Re: [PATCH v4 09/11] ARM64: kernel: add support for cpu cache information

[Will Deacon]

Hi Sudeep,

On Wed, Sep 03, 2014 at 06:00:15PM +0100, Sudeep Holla wrote:
> From: Sudeep Holla <sudeep.holla@xxxxxxx>
> 
> This patch adds support for cacheinfo on ARM64.
> 
> On ARMv8, the cache hierarchy can be identified through Cache Level ID
> (CLIDR) register while the cache geometry is provided by Cache Size ID
> (CCSIDR) register.
> 
> Since the architecture doesn't provide any way of detecting the cpus
> sharing particular cache, device tree is used for the same purpose.

Out of interest, what's this actually for? Is there something useful in
userspace that will lap this out of sysfs? If so, it would be great if those
people could take these patches for a spin.

> diff --git a/arch/arm64/kernel/cacheinfo.c b/arch/arm64/kernel/cacheinfo.c
> new file mode 100644
> index 000000000000..a9cbf3b40a1f
> --- /dev/null
> +++ b/arch/arm64/kernel/cacheinfo.c
> @@ -0,0 +1,142 @@
> +/*
> + *  ARM64 cacheinfo support
> + *
> + *  Copyright (C) 2014 ARM Ltd.
> + *  All Rights Reserved
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed "as is" WITHOUT ANY WARRANTY of any
> + * kind, whether express or implied; without even the implied warranty
> + * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/bitops.h>
> +#include <linux/cacheinfo.h>
> +#include <linux/cpu.h>
> +#include <linux/compiler.h>
> +#include <linux/of.h>
> +
> +#include <asm/processor.h>
> +
> +#define MAX_CACHE_LEVEL			7	/* Max 7 level supported */
> +/* Ctypen, bits[3(n - 1) + 2 : 3(n - 1)], for n = 1 to 7 */
> +#define CLIDR_CTYPE_SHIFT(level)	(3 * (level - 1))
> +#define CLIDR_CTYPE_MASK(level)		(7 << CLIDR_CTYPE_SHIFT(level))
> +#define CLIDR_CTYPE(clidr, level)	\
> +	(((clidr) & CLIDR_CTYPE_MASK(level)) >> CLIDR_CTYPE_SHIFT(level))
> +
> +static inline enum cache_type get_cache_type(int level)
> +{
> +	u64 clidr;
> +
> +	if (level > MAX_CACHE_LEVEL)
> +		return CACHE_TYPE_NOCACHE;
> +	asm volatile ("mrs     %x0, clidr_el1" : "=r" (clidr));
> +	return CLIDR_CTYPE(clidr, level);
> +}
> +
> +/*
> + * NumSets, bits[27:13] - (Number of sets in cache) - 1
> + * Associativity, bits[12:3] - (Associativity of cache) - 1
> + * LineSize, bits[2:0] - (Log2(Number of words in cache line)) - 2
> + */
> +#define CCSIDR_WRITE_THROUGH		BIT(31)
> +#define CCSIDR_WRITE_BACK		BIT(30)
> +#define CCSIDR_READ_ALLOCATE		BIT(29)
> +#define CCSIDR_WRITE_ALLOCATE		BIT(28)
> +#define CCSIDR_LINESIZE_MASK		0x7
> +#define CCSIDR_ASSOCIATIVITY_SHIFT	3
> +#define CCSIDR_ASSOCIATIVITY_MASK	0x3FF
> +#define CCSIDR_NUMSETS_SHIFT		13
> +#define CCSIDR_NUMSETS_MASK		0x7FF
> +
> +/*
> + * Which cache CCSIDR represents depends on CSSELR value
> + * Make sure no one else changes CSSELR during this
> + * smp_call_function_single prevents preemption for us
> + */
> +static inline u32 get_ccsidr(u64 csselr)
> +{
> +	u64 ccsidr;
> +
> +	/* Put value into CSSELR */
> +	asm volatile("msr csselr_el1, %x0" : : "r" (csselr));
> +	isb();
> +	/* Read result out of CCSIDR */
> +	asm volatile("mrs %x0, ccsidr_el1" : "=r" (ccsidr));
> +
> +	return (u32)ccsidr;

Since you're using %x0, can you just make ccsidr a u32?

Also, we have icache_get_ccsidr in kernel/cpuinfo.c already, as well as
some parsing constants in asm/cachetype.h. Can you try to clean up some of
the duplication/needless split please? (moving this helper and the #defines
out would be a good start).

Will

> +}
> +
> +static void ci_leaf_init(struct cacheinfo *this_leaf,
> +			 enum cache_type type, unsigned int level)
> +{
> +	bool is_instr_cache = type & CACHE_TYPE_INST;
> +	u32 tmp = get_ccsidr((level - 1) << 1 | is_instr_cache);
> +
> +	this_leaf->level = level;
> +	this_leaf->type = type;
> +	this_leaf->coherency_line_size =
> +	    (1 << ((tmp & CCSIDR_LINESIZE_MASK) + 2)) * 4;
> +	this_leaf->number_of_sets =
> +	    ((tmp >> CCSIDR_NUMSETS_SHIFT) & CCSIDR_NUMSETS_MASK) + 1;
> +	this_leaf->ways_of_associativity = ((tmp >> CCSIDR_ASSOCIATIVITY_SHIFT)
> +					    & CCSIDR_ASSOCIATIVITY_MASK) + 1;
> +	this_leaf->size = this_leaf->number_of_sets *
> +	    this_leaf->coherency_line_size * this_leaf->ways_of_associativity;
> +	this_leaf->attributes =
> +		((tmp & CCSIDR_WRITE_THROUGH) ? CACHE_WRITE_THROUGH : 0) |
> +		((tmp & CCSIDR_WRITE_BACK) ? CACHE_WRITE_BACK : 0) |
> +		((tmp & CCSIDR_READ_ALLOCATE) ? CACHE_READ_ALLOCATE : 0) |
> +		((tmp & CCSIDR_WRITE_ALLOCATE) ? CACHE_WRITE_ALLOCATE : 0);
> +}
> +
> +static int __init_cache_level(unsigned int cpu)
> +{
> +	unsigned int ctype, level, leaves;
> +	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> +
> +	for (level = 1, leaves = 0; level <= MAX_CACHE_LEVEL; level++) {
> +		ctype = get_cache_type(level);
> +		if (ctype == CACHE_TYPE_NOCACHE) {
> +			level--;
> +			break;
> +		}
> +		/* Separate instruction and data caches */
> +		leaves += (ctype == CACHE_TYPE_SEPARATE) ? 2 : 1;
> +	}
> +
> +	this_cpu_ci->num_levels = level;
> +	this_cpu_ci->num_leaves = leaves;
> +	return 0;
> +}
> +
> +static int __populate_cache_leaves(unsigned int cpu)
> +{
> +	unsigned int level, idx;
> +	enum cache_type type;
> +	struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
> +	struct cacheinfo *this_leaf = this_cpu_ci->info_list;
> +
> +	for (idx = 0, level = 1; level <= this_cpu_ci->num_levels &&
> +	     idx < this_cpu_ci->num_leaves; idx++, level++) {
> +		type = get_cache_type(level);
> +		if (type == CACHE_TYPE_SEPARATE) {
> +			ci_leaf_init(this_leaf++, CACHE_TYPE_DATA, level);
> +			ci_leaf_init(this_leaf++, CACHE_TYPE_INST, level);
> +		} else {
> +			ci_leaf_init(this_leaf++, type, level);
> +		}
> +	}
> +	return 0;
> +}
> +
> +DEFINE_SMP_CALL_CACHE_FUNCTION(init_cache_level)
> +DEFINE_SMP_CALL_CACHE_FUNCTION(populate_cache_leaves)
> -- 
> 1.8.3.2
> 
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