[PATCH 2/9] RISC-V: Add Zicboz detection and block size parsing

[Andrew Jones]

Mostly follow the same pattern as Zicbom, but leave out the toolchain
checks as we plan to use the insn-def framework for the cbo.zero
instruction.

Signed-off-by: Andrew Jones <ajones at ventanamicro.com>
---
 arch/riscv/Kconfig                  | 13 +++++++++++++
 arch/riscv/include/asm/cacheflush.h |  3 ++-
 arch/riscv/include/asm/hwcap.h      |  1 +
 arch/riscv/kernel/cpu.c             |  1 +
 arch/riscv/kernel/cpufeature.c      | 10 ++++++++++
 arch/riscv/kernel/setup.c           |  2 +-
 arch/riscv/mm/cacheflush.c          | 23 +++++++++++++++--------
 7 files changed, 43 insertions(+), 10 deletions(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index 6b48a3ae9843..c20e6fa0c0b1 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -433,6 +433,19 @@ config RISCV_ISA_ZICBOM
 
 	   If you don't know what to do here, say Y.
 
+config RISCV_ISA_ZICBOZ
+	bool "Zicboz extension support for faster zeroing of memory"
+	depends on !XIP_KERNEL && MMU
+	select RISCV_ALTERNATIVE
+	default y
+	help
+	   Adds support to dynamically detect the presence of the ZICBOZ
+	   extension (cbo.zero instruction) and enable its usage.
+
+	   The Zicboz extension is used for faster zeroing of memory.
+
+	   If you don't know what to do here, say Y.
+
 config FPU
 	bool "FPU support"
 	default y
diff --git a/arch/riscv/include/asm/cacheflush.h b/arch/riscv/include/asm/cacheflush.h
index f6fbe7042f1c..5b31568cf5e6 100644
--- a/arch/riscv/include/asm/cacheflush.h
+++ b/arch/riscv/include/asm/cacheflush.h
@@ -43,7 +43,8 @@ void flush_icache_mm(struct mm_struct *mm, bool local);
 #endif /* CONFIG_SMP */
 
 extern unsigned int riscv_cbom_block_size;
-void riscv_init_cbom_blocksize(void);
+extern unsigned int riscv_cboz_block_size;
+void riscv_init_cbo_blocksizes(void);
 
 #ifdef CONFIG_RISCV_DMA_NONCOHERENT
 void riscv_noncoherent_supported(void);
diff --git a/arch/riscv/include/asm/hwcap.h b/arch/riscv/include/asm/hwcap.h
index 5d6492bde446..eaa5a972ad2d 100644
--- a/arch/riscv/include/asm/hwcap.h
+++ b/arch/riscv/include/asm/hwcap.h
@@ -45,6 +45,7 @@
 #define RISCV_ISA_EXT_ZIHINTPAUSE	29
 #define RISCV_ISA_EXT_SSTC		30
 #define RISCV_ISA_EXT_SVINVAL		31
+#define RISCV_ISA_EXT_ZICBOZ		32
 
 #define RISCV_ISA_EXT_ID_MAX		RISCV_ISA_EXT_MAX
 
diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index fa427bdcf773..bf969218f609 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -144,6 +144,7 @@ static struct riscv_isa_ext_data isa_ext_arr[] = {
 	__RISCV_ISA_EXT_DATA(svpbmt, RISCV_ISA_EXT_SVPBMT),
 	__RISCV_ISA_EXT_DATA(zicbom, RISCV_ISA_EXT_ZICBOM),
 	__RISCV_ISA_EXT_DATA(zihintpause, RISCV_ISA_EXT_ZIHINTPAUSE),
+	__RISCV_ISA_EXT_DATA(zicboz, RISCV_ISA_EXT_ZICBOZ),
 	__RISCV_ISA_EXT_DATA("", RISCV_ISA_EXT_MAX),
 };
 
diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index 18b9ed4df1f4..e13b3391de76 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -78,6 +78,15 @@ static bool riscv_isa_extension_check(int id)
 			return false;
 		}
 		return true;
+	case RISCV_ISA_EXT_ZICBOZ:
+		if (!riscv_cboz_block_size) {
+			pr_err("Zicboz detected in ISA string, but no cboz-block-size found\n");
+			return false;
+		} else if (!is_power_of_2(riscv_cboz_block_size)) {
+			pr_err("cboz-block-size present, but is not a power-of-2\n");
+			return false;
+		}
+		return true;
 	}
 
 	return true;
@@ -225,6 +234,7 @@ void __init riscv_fill_hwcap(void)
 				SET_ISA_EXT_MAP("zihintpause", RISCV_ISA_EXT_ZIHINTPAUSE);
 				SET_ISA_EXT_MAP("sstc", RISCV_ISA_EXT_SSTC);
 				SET_ISA_EXT_MAP("svinval", RISCV_ISA_EXT_SVINVAL);
+				SET_ISA_EXT_MAP("zicboz", RISCV_ISA_EXT_ZICBOZ);
 			}
 #undef SET_ISA_EXT_MAP
 		}
diff --git a/arch/riscv/kernel/setup.c b/arch/riscv/kernel/setup.c
index a07917551027..26de0d8fd23d 100644
--- a/arch/riscv/kernel/setup.c
+++ b/arch/riscv/kernel/setup.c
@@ -296,7 +296,7 @@ void __init setup_arch(char **cmdline_p)
 	setup_smp();
 #endif
 
-	riscv_init_cbom_blocksize();
+	riscv_init_cbo_blocksizes();
 	riscv_fill_hwcap();
 	apply_boot_alternatives();
 #ifdef CONFIG_RISCV_DMA_NONCOHERENT
diff --git a/arch/riscv/mm/cacheflush.c b/arch/riscv/mm/cacheflush.c
index f096b9966cae..208e0d58bde3 100644
--- a/arch/riscv/mm/cacheflush.c
+++ b/arch/riscv/mm/cacheflush.c
@@ -91,6 +91,9 @@ void flush_icache_pte(pte_t pte)
 unsigned int riscv_cbom_block_size;
 EXPORT_SYMBOL_GPL(riscv_cbom_block_size);
 
+unsigned int riscv_cboz_block_size;
+EXPORT_SYMBOL_GPL(riscv_cboz_block_size);
+
 static void cbo_get_block_size(struct device_node *node,
 			       const char *name, u32 *blksz,
 			       unsigned long *first_hartid)
@@ -113,19 +116,23 @@ static void cbo_get_block_size(struct device_node *node,
 	}
 }
 
-void riscv_init_cbom_blocksize(void)
+void riscv_init_cbo_blocksizes(void)
 {
+	unsigned long cbom_hartid, cboz_hartid;
+	u32 cbom_blksz = 0, cboz_blksz = 0;
 	struct device_node *node;
-	unsigned long cbom_hartid;
-	u32 probed_block_size;
 
-	probed_block_size = 0;
 	for_each_of_cpu_node(node) {
-		/* set block-size for cbom extension if available */
+		/* set block-size for cbom and/or cboz extension if available */
 		cbo_get_block_size(node, "riscv,cbom-block-size",
-				   &probed_block_size, &cbom_hartid);
+				   &cbom_blksz, &cbom_hartid);
+		cbo_get_block_size(node, "riscv,cboz-block-size",
+				   &cboz_blksz, &cboz_hartid);
 	}
 
-	if (probed_block_size)
-		riscv_cbom_block_size = probed_block_size;
+	if (cbom_blksz)
+		riscv_cbom_block_size = cbom_blksz;
+
+	if (cboz_blksz)
+		riscv_cboz_block_size = cboz_blksz;
 }
-- 
2.37.3