linux-kernel - [v4 PATCH 8/8] RISC-V: Assign hwcap as per comman capabilities.

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Message-Id: <1549969812-22502-9-git-send-email-atish.patra@wdc.com>
Date:   Tue, 12 Feb 2019 03:10:12 -0800
From:   Atish Patra <atish.patra@....com>
To:     linux-riscv@...ts.infradead.org
Cc:     Atish Patra <atish.patra@....com>,
        Alan Kao <alankao@...estech.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Andreas Schwab <schwab@...e.de>,
        Anup Patel <anup@...infault.org>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Dmitriy Cherkasov <dmitriy@...-tech.org>,
        Jason Cooper <jason@...edaemon.net>,
        Johan Hovold <johan@...nel.org>, linux-kernel@...r.kernel.org,
        Marc Zyngier <marc.zyngier@....com>,
        Palmer Dabbelt <palmer@...ive.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Rob Herring <robh@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: [v4 PATCH 8/8] RISC-V: Assign hwcap as per comman capabilities.

Currently, we set hwcap based on first valid hart from DT. This may not
be correct always as that hart might not be current booting cpu or may
have a different capability.

Set hwcap as the capabilities supported by all possible harts with "okay"
status.

Signed-off-by: Atish Patra <atish.patra@....com>
---
 arch/riscv/kernel/cpufeature.c | 41 ++++++++++++++++++++++-------------------
 1 file changed, 22 insertions(+), 19 deletions(-)

diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
index e7a4701f..a1e4fb34 100644
--- a/arch/riscv/kernel/cpufeature.c
+++ b/arch/riscv/kernel/cpufeature.c
@@ -20,6 +20,7 @@
 #include <linux/of.h>
 #include <asm/processor.h>
 #include <asm/hwcap.h>
+#include <asm/smp.h>
 
 unsigned long elf_hwcap __read_mostly;
 #ifdef CONFIG_FPU
@@ -42,28 +43,30 @@ void riscv_fill_hwcap(void)
 
 	elf_hwcap = 0;
 
-	/*
-	 * We don't support running Linux on hertergenous ISA systems.  For
-	 * now, we just check the ISA of the first "okay" processor.
-	 */
 	for_each_of_cpu_node(node) {
-		if (riscv_of_processor_hartid(node) >= 0)
-			break;
-	}
-	if (!node) {
-		pr_warn("Unable to find \"cpu\" devicetree entry\n");
-		return;
-	}
+		unsigned long this_hwcap = 0;
 
-	if (of_property_read_string(node, "riscv,isa", &isa)) {
-		pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
-		of_node_put(node);
-		return;
-	}
-	of_node_put(node);
+		if (riscv_of_processor_hartid(node) < 0)
+			continue;
 
-	for (i = 0; i < strlen(isa); ++i)
-		elf_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
+		if (of_property_read_string(node, "riscv,isa", &isa)) {
+			pr_warn("Unable to find \"riscv,isa\" devicetree entry\n");
+			return;
+		}
+
+		for (i = 0; i < strlen(isa); ++i)
+			this_hwcap |= isa2hwcap[(unsigned char)(isa[i])];
+
+		/*
+		 * All "okay" hart should have same isa. Set HWCAP based on
+		 * common capabilities of every "okay" hart, in case they don't
+		 * have.
+		 */
+		if (elf_hwcap)
+			elf_hwcap &= this_hwcap;
+		else
+			elf_hwcap = this_hwcap;
+	}
 
 	/* We don't support systems with F but without D, so mask those out
 	 * here. */
-- 
2.7.4