From: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Date: Fri, 29 Jul 2022 15:12:25 +0000 (+0100)
Subject: ARM: findbit: document ARMv5 bit offset calculation
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=7e0093870e6c550139a27d1780f54f1e8acc4978;p=linux.git

ARM: findbit: document ARMv5 bit offset calculation

Document the ARMv5 bit offset calculation code.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
---

diff --git a/arch/arm/lib/findbit.S b/arch/arm/lib/findbit.S
index 7fd3600db8efd..4c584bc4704b8 100644
--- a/arch/arm/lib/findbit.S
+++ b/arch/arm/lib/findbit.S
@@ -172,10 +172,10 @@ ENDPROC(_find_next_bit_be)
 .L_found:
 #if __LINUX_ARM_ARCH__ >= 5
 		rsb	r0, r3, #0
-		and	r3, r3, r0
-		clz	r3, r3
-		rsb	r3, r3, #31
-		add	r0, r2, r3
+		and	r3, r3, r0		@ mask out lowest bit set
+		clz	r3, r3			@ count high zero bits
+		rsb	r3, r3, #31		@ offset of first set bit
+		add	r0, r2, r3		@ add offset of first set bit
 #else
 		tst	r3, #0x0f
 		addeq	r2, r2, #4