[PATCH v2] openrisc: Add cacheinfo support

Sahil Siddiq
2025-03-15T20:40:42Z

Add cacheinfo support for OpenRISC.

Currently, a few CPU cache attributes pertaining to OpenRISC processors
are exposed along with other unrelated CPU attributes in the procfs file
system (/proc/cpuinfo). However, a few cache attributes remain unexposed.
An attempt is also made to pull these CPU cache attributes without
detecting if the relevant cache exists.

This patch provides a mechanism that the generic cacheinfo infrastructure
can employ to expose these attributes via the sysfs file system. These
attributes are exposed in /sys/devices/system/cpu/cpuX/cache/indexN.
Cache attributes are pulled only when the cache component is detected.

The implementation to pull cache attributes from the processor's
registers has been moved from arch/openrisc/kernel/setup.c with a few
modifications.

The patch also moves cache-related fields out of struct cpuinfo_or1k and
into its own struct to keep the implementation straightforward. This
reduces duplication of cache-related fields while keeping cpuinfo_or1k
extensible in case more cache descriptors are added in the future.

This implementation is based on similar work done for MIPS and LoongArch.

Signed-off-by: Sahil Siddiq <sahilcdq@proton.me>
---
Changes from v1 -> v2:
- Changed patch prefix from RFC to PATCH.
- cacheinfo.c: Print number of sets. Remove integer padding.
- dma.c
(page_set_nocache): Access cache attributes only if component exists.
(arch_sync_dma_for_device): Likewise.
- cache.c: Likewise.
- init.c: Likewise.

arch/openrisc/include/asm/cpuinfo.h | 16 +++--
arch/openrisc/kernel/Makefile | 2 +-
arch/openrisc/kernel/cacheinfo.c | 106 ++++++++++++++++++++++++++++
arch/openrisc/kernel/dma.c | 22 +++---
arch/openrisc/kernel/setup.c | 45 ------------
arch/openrisc/mm/cache.c | 11 ++-
arch/openrisc/mm/init.c | 8 ++-
7 files changed, 144 insertions(+), 66 deletions(-)
create mode 100644 arch/openrisc/kernel/cacheinfo.c

diff --git a/arch/openrisc/include/asm/cpuinfo.h b/arch/openrisc/include/asm/cpuinfo.h
index 5e4744153d0e..82f5d4c06314 100644
--- a/arch/openrisc/include/asm/cpuinfo.h
+++ b/arch/openrisc/include/asm/cpuinfo.h
@@ -15,16 +15,18 @@
#ifndef __ASM_OPENRISC_CPUINFO_H
#define __ASM_OPENRISC_CPUINFO_H

+struct cache_desc {
+ u32 size;
+ u32 sets;
+ u32 block_size;
+ u32 ways;
+};
+
struct cpuinfo_or1k {
u32 clock_frequency;

- u32 icache_size;
- u32 icache_block_size;
- u32 icache_ways;
-
- u32 dcache_size;
- u32 dcache_block_size;
- u32 dcache_ways;
+ struct cache_desc icache;
+ struct cache_desc dcache;

u16 coreid;
};
diff --git a/arch/openrisc/kernel/Makefile b/arch/openrisc/kernel/Makefile
index 79129161f3e0..e4c7d9bdd598 100644
--- a/arch/openrisc/kernel/Makefile
+++ b/arch/openrisc/kernel/Makefile
@@ -7,7 +7,7 @@ extra-y := vmlinux.lds

obj-y := head.o setup.o or32_ksyms.o process.o dma.o \
traps.o time.o irq.o entry.o ptrace.o signal.o \
- sys_call_table.o unwinder.o
+ sys_call_table.o unwinder.o cacheinfo.o

obj-$(CONFIG_SMP) += smp.o sync-timer.o
obj-$(CONFIG_STACKTRACE) += stacktrace.o
diff --git a/arch/openrisc/kernel/cacheinfo.c b/arch/openrisc/kernel/cacheinfo.c
new file mode 100644
index 000000000000..6bb81e246f7e
--- /dev/null
+++ b/arch/openrisc/kernel/cacheinfo.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * OpenRISC cacheinfo support
+ *
+ * Based on work done for MIPS and LoongArch. All original copyrights
+ * apply as per the original source declaration.
+ *
+ * OpenRISC implementation:
+ * Copyright (C) 2025 Sahil Siddiq <sahilcdq@proton.me>
+ */
+
+#include <linux/cacheinfo.h>
+#include <asm/cpuinfo.h>
+#include <asm/spr.h>
+#include <asm/spr_defs.h>
+
+static inline void ci_leaf_init(struct cacheinfo *this_leaf, enum cache_type type,
+ unsigned int level, struct cache_desc *cache, int cpu)
+{
+ this_leaf->type = type;
+ this_leaf->level = level;
+ this_leaf->coherency_line_size = cache->block_size;
+ this_leaf->number_of_sets = cache->sets;
+ this_leaf->ways_of_associativity = cache->ways;
+ this_leaf->size = cache->size;
+ cpumask_set_cpu(cpu, &this_leaf->shared_cpu_map);
+}
+
+int init_cache_level(unsigned int cpu)
+{
+ struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
+ struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+ int leaves = 0, levels = 0;
+ unsigned long upr = mfspr(SPR_UPR);
+ unsigned long iccfgr, dccfgr;
+
+ if (!(upr & SPR_UPR_UP)) {
+ printk(KERN_INFO
+ "-- no UPR register... unable to detect configuration\n");
+ return -ENOENT;
+ }
+
+ if (upr & SPR_UPR_DCP) {
+ dccfgr = mfspr(SPR_DCCFGR);
+ cpuinfo->dcache.ways = 1 << (dccfgr & SPR_DCCFGR_NCW);
+ cpuinfo->dcache.sets = 1 << ((dccfgr & SPR_DCCFGR_NCS) >> 3);
+ cpuinfo->dcache.block_size = 16 << ((dccfgr & SPR_DCCFGR_CBS) >> 7);
+ cpuinfo->dcache.size =
+ cpuinfo->dcache.sets * cpuinfo->dcache.ways * cpuinfo->dcache.block_size;
+ leaves += 1;
+ printk(KERN_INFO
+ "-- dcache: %d bytes total, %d bytes/line, %d set(s), %d way(s)\n",
+ cpuinfo->dcache.size, cpuinfo->dcache.block_size,
+ cpuinfo->dcache.sets,
+ cpuinfo->dcache.ways);
+ } else
+ printk(KERN_INFO "-- dcache disabled\n");
+
+ if (upr & SPR_UPR_ICP) {
+ iccfgr = mfspr(SPR_ICCFGR);
+ cpuinfo->icache.ways = 1 << (iccfgr & SPR_ICCFGR_NCW);
+ cpuinfo->icache.sets = 1 << ((iccfgr & SPR_ICCFGR_NCS) >> 3);
+ cpuinfo->icache.block_size = 16 << ((iccfgr & SPR_ICCFGR_CBS) >> 7);
+ cpuinfo->icache.size =
+ cpuinfo->icache.sets * cpuinfo->icache.ways * cpuinfo->icache.block_size;
+ leaves += 1;
+ printk(KERN_INFO
+ "-- icache: %d bytes total, %d bytes/line, %d set(s), %d way(s)\n",
+ cpuinfo->icache.size, cpuinfo->icache.block_size,
+ cpuinfo->icache.sets,
+ cpuinfo->icache.ways);
+ } else
+ printk(KERN_INFO "-- icache disabled\n");
+
+ if (!leaves)
+ return -ENOENT;
+
+ levels = 1;
+
+ this_cpu_ci->num_leaves = leaves;
+ this_cpu_ci->num_levels = levels;
+
+ return 0;
+}
+
+int populate_cache_leaves(unsigned int cpu)
+{
+ struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[smp_processor_id()];
+ struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
+ struct cacheinfo *this_leaf = this_cpu_ci->info_list;
+ int level = 1;
+
+ if (cpuinfo->dcache.ways) {
+ ci_leaf_init(this_leaf, CACHE_TYPE_DATA, level, &cpuinfo->dcache, cpu);
+ this_leaf->attributes = ((mfspr(SPR_DCCFGR) & SPR_DCCFGR_CWS) >> 8) ?
+ CACHE_WRITE_BACK : CACHE_WRITE_THROUGH;
+ this_leaf++;
+ }
+
+ if (cpuinfo->icache.ways)
+ ci_leaf_init(this_leaf, CACHE_TYPE_INST, level, &cpuinfo->icache, cpu);
+
+ this_cpu_ci->cpu_map_populated = true;
+
+ return 0;
+}
diff --git a/arch/openrisc/kernel/dma.c b/arch/openrisc/kernel/dma.c
index b3edbb33b621..ffb161e41e9d 100644
--- a/arch/openrisc/kernel/dma.c
+++ b/arch/openrisc/kernel/dma.c
@@ -36,8 +36,10 @@ page_set_nocache(pte_t *pte, unsigned long addr,
flush_tlb_kernel_range(addr, addr + PAGE_SIZE);

/* Flush page out of dcache */
- for (cl = __pa(addr); cl < __pa(next); cl += cpuinfo->dcache_block_size)
- mtspr(SPR_DCBFR, cl);
+ if (cpuinfo->dcache.ways) {
+ for (cl = __pa(addr); cl < __pa(next); cl += cpuinfo->dcache.block_size)
+ mtspr(SPR_DCBFR, cl);
+ }

return 0;
}
@@ -104,15 +106,19 @@ void arch_sync_dma_for_device(phys_addr_t addr, size_t size,
switch (dir) {
case DMA_TO_DEVICE:
/* Flush the dcache for the requested range */
- for (cl = addr; cl < addr + size;
- cl += cpuinfo->dcache_block_size)
- mtspr(SPR_DCBFR, cl);
+ if (cpuinfo->dcache.ways) {
+ for (cl = addr; cl < addr + size;
+ cl += cpuinfo->dcache.block_size)
+ mtspr(SPR_DCBFR, cl);
+ }
break;
case DMA_FROM_DEVICE:
/* Invalidate the dcache for the requested range */
- for (cl = addr; cl < addr + size;
- cl += cpuinfo->dcache_block_size)
- mtspr(SPR_DCBIR, cl);
+ if (cpuinfo->dcache.ways) {
+ for (cl = addr; cl < addr + size;
+ cl += cpuinfo->dcache.block_size)
+ mtspr(SPR_DCBIR, cl);
+ }
break;
default:
/*
diff --git a/arch/openrisc/kernel/setup.c b/arch/openrisc/kernel/setup.c
index be56eaafc8b9..38172c0989cf 100644
--- a/arch/openrisc/kernel/setup.c
+++ b/arch/openrisc/kernel/setup.c
@@ -107,27 +107,6 @@ static void print_cpuinfo(void)
printk(KERN_INFO "CPU: OpenRISC-%x (revision %d) @%d MHz\n",
version, revision, cpuinfo->clock_frequency / 1000000);

- if (!(upr & SPR_UPR_UP)) {
- printk(KERN_INFO
- "-- no UPR register... unable to detect configuration\n");
- return;
- }
-
- if (upr & SPR_UPR_DCP)
- printk(KERN_INFO
- "-- dcache: %4d bytes total, %2d bytes/line, %d way(s)\n",
- cpuinfo->dcache_size, cpuinfo->dcache_block_size,
- cpuinfo->dcache_ways);
- else
- printk(KERN_INFO "-- dcache disabled\n");
- if (upr & SPR_UPR_ICP)
- printk(KERN_INFO
- "-- icache: %4d bytes total, %2d bytes/line, %d way(s)\n",
- cpuinfo->icache_size, cpuinfo->icache_block_size,
- cpuinfo->icache_ways);
- else
- printk(KERN_INFO "-- icache disabled\n");
-
if (upr & SPR_UPR_DMP)
printk(KERN_INFO "-- dmmu: %4d entries, %lu way(s)\n",
1 << ((mfspr(SPR_DMMUCFGR) & SPR_DMMUCFGR_NTS) >> 2),
@@ -155,8 +134,6 @@ static void print_cpuinfo(void)
void __init setup_cpuinfo(void)
{
struct device_node *cpu;
- unsigned long iccfgr, dccfgr;
- unsigned long cache_set_size;
int cpu_id = smp_processor_id();
struct cpuinfo_or1k *cpuinfo = &cpuinfo_or1k[cpu_id];

@@ -164,20 +141,6 @@ void __init setup_cpuinfo(void)
if (!cpu)
panic("Couldn't find CPU%d in device tree...\n", cpu_id);

- iccfgr = mfspr(SPR_ICCFGR);
- cpuinfo->icache_ways = 1 << (iccfgr & SPR_ICCFGR_NCW);
- cache_set_size = 1 << ((iccfgr & SPR_ICCFGR_NCS) >> 3);
- cpuinfo->icache_block_size = 16 << ((iccfgr & SPR_ICCFGR_CBS) >> 7);
- cpuinfo->icache_size =
- cache_set_size * cpuinfo->icache_ways * cpuinfo->icache_block_size;
-
- dccfgr = mfspr(SPR_DCCFGR);
- cpuinfo->dcache_ways = 1 << (dccfgr & SPR_DCCFGR_NCW);
- cache_set_size = 1 << ((dccfgr & SPR_DCCFGR_NCS) >> 3);
- cpuinfo->dcache_block_size = 16 << ((dccfgr & SPR_DCCFGR_CBS) >> 7);
- cpuinfo->dcache_size =
- cache_set_size * cpuinfo->dcache_ways * cpuinfo->dcache_block_size;
-
if (of_property_read_u32(cpu, "clock-frequency",
&cpuinfo->clock_frequency)) {
printk(KERN_WARNING
@@ -320,14 +283,6 @@ static int show_cpuinfo(struct seq_file *m, void *v)
seq_printf(m, "revision\t\t: %d\n", vr & SPR_VR_REV);
}
seq_printf(m, "frequency\t\t: %ld\n", loops_per_jiffy * HZ);
- seq_printf(m, "dcache size\t\t: %d bytes\n", cpuinfo->dcache_size);
- seq_printf(m, "dcache block size\t: %d bytes\n",
- cpuinfo->dcache_block_size);
- seq_printf(m, "dcache ways\t\t: %d\n", cpuinfo->dcache_ways);
- seq_printf(m, "icache size\t\t: %d bytes\n", cpuinfo->icache_size);
- seq_printf(m, "icache block size\t: %d bytes\n",
- cpuinfo->icache_block_size);
- seq_printf(m, "icache ways\t\t: %d\n", cpuinfo->icache_ways);
seq_printf(m, "immu\t\t\t: %d entries, %lu ways\n",
1 << ((mfspr(SPR_DMMUCFGR) & SPR_DMMUCFGR_NTS) >> 2),
1 + (mfspr(SPR_DMMUCFGR) & SPR_DMMUCFGR_NTW));
diff --git a/arch/openrisc/mm/cache.c b/arch/openrisc/mm/cache.c
index eb43b73f3855..acdf2dc256bf 100644
--- a/arch/openrisc/mm/cache.c
+++ b/arch/openrisc/mm/cache.c
@@ -16,10 +16,15 @@
#include <asm/cacheflush.h>
#include <asm/tlbflush.h>

-static __always_inline void cache_loop(struct page *page, const unsigned int reg)
+static __always_inline void cache_loop(struct page *page, const unsigned int reg,
+ const unsigned int cache_type)
{
unsigned long paddr = page_to_pfn(page) << PAGE_SHIFT;
unsigned long line = paddr & ~(L1_CACHE_BYTES - 1);
+ unsigned long upr = mfspr(SPR_UPR);
+
+ if (!(upr & SPR_UPR_UP & cache_type))
+ return;

while (line < paddr + PAGE_SIZE) {
mtspr(reg, line);
@@ -29,13 +34,13 @@ static __always_inline void cache_loop(struct page *page, const unsigned int reg

void local_dcache_page_flush(struct page *page)
{
- cache_loop(page, SPR_DCBFR);
+ cache_loop(page, SPR_DCBFR, SPR_UPR_DCP);
}
EXPORT_SYMBOL(local_dcache_page_flush);

void local_icache_page_inv(struct page *page)
{
- cache_loop(page, SPR_ICBIR);
+ cache_loop(page, SPR_ICBIR, SPR_UPR_ICP);
}
EXPORT_SYMBOL(local_icache_page_inv);

diff --git a/arch/openrisc/mm/init.c b/arch/openrisc/mm/init.c
index d0cb1a0126f9..bbe16546c5b9 100644
--- a/arch/openrisc/mm/init.c
+++ b/arch/openrisc/mm/init.c
@@ -124,6 +124,7 @@ static void __init map_ram(void)
void __init paging_init(void)
{
int i;
+ unsigned long upr;

printk(KERN_INFO "Setting up paging and PTEs.\n");

@@ -176,8 +177,11 @@ void __init paging_init(void)
barrier();

/* Invalidate instruction caches after code modification */
- mtspr(SPR_ICBIR, 0x900);
- mtspr(SPR_ICBIR, 0xa00);
+ upr = mfspr(SPR_UPR);
+ if (upr & SPR_UPR_UP & SPR_UPR_ICP) {
+ mtspr(SPR_ICBIR, 0x900);
+ mtspr(SPR_ICBIR, 0xa00);
+ }

/* New TLB miss handlers and kernel page tables are in now place.
* Make sure that page flags get updated for all pages in TLB by
--
2.48.1