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c931680cfa
This patch adds an architecture specific early cache level detection
handler for arm64. This is basically the CLIDR_EL1 based detection that
was previously done (only) in init_cache_level().
This is part of a patch series that attempts to further the work in
commit 5944ce092b ("arch_topology: Build cacheinfo from primary CPU").
Previously, in the absence of any DT/ACPI cache info, architecture
specific cache detection and info allocation for secondary CPUs would
happen in non-preemptible context during early CPU initialization and
trigger a "BUG: sleeping function called from invalid context" splat on
an RT kernel.
This patch does not solve the problem completely for RT kernels. It
relies on the assumption that on most systems, the CPUs are symmetrical
and therefore have the same number of cache leaves. The cacheinfo memory
is allocated early (on the primary CPU), relying on the new handler. If
later (when CLIDR_EL1 based detection runs again on the secondary CPU)
the initial assumption proves to be wrong and the CPU has in fact more
leaves, the cacheinfo memory is reallocated, and that still triggers a
splat on an RT kernel.
In other words, asymmetrical CPU systems *must* still provide cacheinfo
data in DT/ACPI to avoid the splat on RT kernels (unless secondary CPUs
happen to have less leaves than the primary CPU). But symmetrical CPU
systems (the majority) can now get away without the additional DT/ACPI
data and rely on CLIDR_EL1 based detection.
Signed-off-by: Radu Rendec <rrendec@redhat.com>
Reviewed-by: Pierre Gondois <pierre.gondois@arm.com>
Link: https://lore.kernel.org/r/20230412185759.755408-3-rrendec@redhat.com
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
118 lines
2.6 KiB
C
118 lines
2.6 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* ARM64 cacheinfo support
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*
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* Copyright (C) 2015 ARM Ltd.
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* All Rights Reserved
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*/
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#include <linux/acpi.h>
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#include <linux/cacheinfo.h>
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#include <linux/of.h>
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#define MAX_CACHE_LEVEL 7 /* Max 7 level supported */
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int cache_line_size(void)
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{
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if (coherency_max_size != 0)
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return coherency_max_size;
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return cache_line_size_of_cpu();
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}
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EXPORT_SYMBOL_GPL(cache_line_size);
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static inline enum cache_type get_cache_type(int level)
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{
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u64 clidr;
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if (level > MAX_CACHE_LEVEL)
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return CACHE_TYPE_NOCACHE;
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clidr = read_sysreg(clidr_el1);
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return CLIDR_CTYPE(clidr, level);
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}
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static void ci_leaf_init(struct cacheinfo *this_leaf,
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enum cache_type type, unsigned int level)
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{
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this_leaf->level = level;
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this_leaf->type = type;
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}
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static void detect_cache_level(unsigned int *level_p, unsigned int *leaves_p)
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{
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unsigned int ctype, level, leaves;
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for (level = 1, leaves = 0; level <= MAX_CACHE_LEVEL; level++) {
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ctype = get_cache_type(level);
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if (ctype == CACHE_TYPE_NOCACHE) {
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level--;
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break;
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}
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/* Separate instruction and data caches */
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leaves += (ctype == CACHE_TYPE_SEPARATE) ? 2 : 1;
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}
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*level_p = level;
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*leaves_p = leaves;
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}
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int early_cache_level(unsigned int cpu)
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{
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struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
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detect_cache_level(&this_cpu_ci->num_levels, &this_cpu_ci->num_leaves);
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return 0;
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}
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int init_cache_level(unsigned int cpu)
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{
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unsigned int level, leaves;
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int fw_level, ret;
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struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
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detect_cache_level(&level, &leaves);
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if (acpi_disabled) {
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fw_level = of_find_last_cache_level(cpu);
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} else {
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ret = acpi_get_cache_info(cpu, &fw_level, NULL);
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if (ret < 0)
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fw_level = 0;
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}
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if (level < fw_level) {
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/*
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* some external caches not specified in CLIDR_EL1
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* the information may be available in the device tree
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* only unified external caches are considered here
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*/
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leaves += (fw_level - level);
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level = fw_level;
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}
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this_cpu_ci->num_levels = level;
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this_cpu_ci->num_leaves = leaves;
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return 0;
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}
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int populate_cache_leaves(unsigned int cpu)
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{
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unsigned int level, idx;
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enum cache_type type;
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struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
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struct cacheinfo *this_leaf = this_cpu_ci->info_list;
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for (idx = 0, level = 1; level <= this_cpu_ci->num_levels &&
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idx < this_cpu_ci->num_leaves; idx++, level++) {
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type = get_cache_type(level);
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if (type == CACHE_TYPE_SEPARATE) {
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ci_leaf_init(this_leaf++, CACHE_TYPE_DATA, level);
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ci_leaf_init(this_leaf++, CACHE_TYPE_INST, level);
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} else {
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ci_leaf_init(this_leaf++, type, level);
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}
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}
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return 0;
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}
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