[RFC PATCH 2/6] arm64: Support ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION

[Jonathan Cameron]

From: Yicong Yang <yangyicong at hisilicon.com>

ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION provides the mechanism for
invalidate certain memory regions in a cache-incoherent manner.
Currently is used by NVIDMM and CXL memory. This is mainly done
by the system component and is implementation define per spec.
Provides a method for the platforms register their own invalidate
method and implement ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION.

Signed-off-by: Yicong Yang <yangyicong at hisilicon.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron at huawei.com>
---
 arch/arm64/Kconfig                  |  1 +
 arch/arm64/include/asm/cacheflush.h | 14 ++++++++++
 arch/arm64/mm/flush.c               | 42 +++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 940343beb3d4..11ecd20ec3b8 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -21,6 +21,7 @@ config ARM64
 	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
 	select ARCH_HAS_CACHE_LINE_SIZE
 	select ARCH_HAS_CC_PLATFORM
+	select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
 	select ARCH_HAS_CRC32
 	select ARCH_HAS_CRC_T10DIF if KERNEL_MODE_NEON
 	select ARCH_HAS_CURRENT_STACK_POINTER
diff --git a/arch/arm64/include/asm/cacheflush.h b/arch/arm64/include/asm/cacheflush.h
index 28ab96e808ef..b8eb8738c965 100644
--- a/arch/arm64/include/asm/cacheflush.h
+++ b/arch/arm64/include/asm/cacheflush.h
@@ -139,6 +139,20 @@ static __always_inline void icache_inval_all_pou(void)
 	dsb(ish);
 }
 
+#ifdef CONFIG_ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
+
+#include <linux/memregion.h>
+
+struct system_cache_flush_method {
+	int (*invalidate_memregion)(int res_desc,
+				    phys_addr_t start, size_t len);
+};
+
+void arm64_set_sys_cache_flush_method(const struct system_cache_flush_method *method);
+void arm64_clr_sys_cache_flush_method(const struct system_cache_flush_method *method);
+
+#endif /* CONFIG_ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION */
+
 #include <asm-generic/cacheflush.h>
 
 #endif /* __ASM_CACHEFLUSH_H */
diff --git a/arch/arm64/mm/flush.c b/arch/arm64/mm/flush.c
index 013eead9b695..d822406d925d 100644
--- a/arch/arm64/mm/flush.c
+++ b/arch/arm64/mm/flush.c
@@ -10,6 +10,7 @@
 #include <linux/mm.h>
 #include <linux/libnvdimm.h>
 #include <linux/pagemap.h>
+#include <linux/memregion.h>
 
 #include <asm/cacheflush.h>
 #include <asm/cache.h>
@@ -100,3 +101,44 @@ void arch_invalidate_pmem(void *addr, size_t size)
 }
 EXPORT_SYMBOL_GPL(arch_invalidate_pmem);
 #endif
+
+#ifdef CONFIG_ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
+
+static const struct system_cache_flush_method *scfm_data;
+DEFINE_SPINLOCK(scfm_lock);
+
+void arm64_set_sys_cache_flush_method(const struct system_cache_flush_method *method)
+{
+	guard(spinlock_irqsave)(&scfm_lock);
+	if (scfm_data || !method || !method->invalidate_memregion)
+		return;
+
+	scfm_data = method;
+}
+EXPORT_SYMBOL_GPL(arm64_set_sys_cache_flush_method);
+
+void arm64_clr_sys_cache_flush_method(const struct system_cache_flush_method *method)
+{
+	guard(spinlock_irqsave)(&scfm_lock);
+	if (scfm_data && scfm_data == method)
+		scfm_data = NULL;
+}
+
+int cpu_cache_invalidate_memregion(int res_desc, phys_addr_t start, size_t len)
+{
+	guard(spinlock_irqsave)(&scfm_lock);
+	if (!scfm_data)
+		return -EOPNOTSUPP;
+
+	return scfm_data->invalidate_memregion(res_desc, start, len);
+}
+EXPORT_SYMBOL_NS_GPL(cpu_cache_invalidate_memregion, "DEVMEM");
+
+bool cpu_cache_has_invalidate_memregion(void)
+{
+	guard(spinlock_irqsave)(&scfm_lock);
+	return !!scfm_data;
+}
+EXPORT_SYMBOL_NS_GPL(cpu_cache_has_invalidate_memregion, "DEVMEM");
+
+#endif /* CONFIG_ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION */
-- 
2.43.0