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From: Matthew Whitehead <tedheadster@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: mingo@kernel.org, tglx@linutronix.de, peterz@infradead.org,
	luto@amacapital.net, bp@alien8.de, hpa@zytor.com,
	Matthew Whitehead <tedheadster@gmail.com>
Subject: [PATCH v2 1/2] x86/cpu: Use correct macros for Cyrix calls
Date: Fri, 21 Sep 2018 17:20:40 -0400	[thread overview]
Message-ID: <20180921212041.13096-2-tedheadster@gmail.com> (raw)
In-Reply-To: <20180921212041.13096-1-tedheadster@gmail.com>

There are comments in processor-cyrix.h advising you to _not_ make calls
using the deprecated macros in this style:

  setCx86_old(CX86_CCR4, getCx86_old(CX86_CCR4) | 0x80);

This is because it expands the macro into a non-functioning calling
sequence. The calling order must be:

  outb(CX86_CCR2, 0x22);
  inb(0x23);

From the comments:

 * When using the old macros a line like
 *   setCx86(CX86_CCR2, getCx86(CX86_CCR2) | 0x88);
 * gets expanded to:
 *  do {
 *    outb((CX86_CCR2), 0x22);
 *    outb((({
 *        outb((CX86_CCR2), 0x22);
 *        inb(0x23);
 *    }) | 0x88), 0x23);
 *  } while (0);

The new macros fix this problem, so we use them instead.

Reviewed-by: Andy Lutomirski <luto@amacapital.net>
Signed-off-by: Matthew Whitehead <tedheadster@gmail.com>
---
 arch/x86/kernel/cpu/cyrix.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/cyrix.c b/arch/x86/kernel/cpu/cyrix.c
index 8949b7ae6d92..d12226f60168 100644
--- a/arch/x86/kernel/cpu/cyrix.c
+++ b/arch/x86/kernel/cpu/cyrix.c
@@ -437,7 +437,7 @@ static void cyrix_identify(struct cpuinfo_x86 *c)
 			/* enable MAPEN  */
 			setCx86(CX86_CCR3, (ccr3 & 0x0f) | 0x10);
 			/* enable cpuid  */
-			setCx86_old(CX86_CCR4, getCx86_old(CX86_CCR4) | 0x80);
+			setCx86(CX86_CCR4, getCx86(CX86_CCR4) | 0x80);
 			/* disable MAPEN */
 			setCx86(CX86_CCR3, ccr3);
 			local_irq_restore(flags);
-- 
2.16.4


  reply	other threads:[~2018-09-21 21:21 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-21 21:20 [PATCH v2 0/2] x86/cpu: Enable cpuid on Cyrix 6x86/6x86L processors Matthew Whitehead
2018-09-21 21:20 ` Matthew Whitehead [this message]
2018-09-22  9:57   ` [tip:x86/cpu] x86/CPU: Use correct macros for Cyrix calls tip-bot for Matthew Whitehead
2018-09-21 21:20 ` [PATCH v2 2/2] x86/cpu: Change query logic so cpuid is enabled before testing Matthew Whitehead
2018-09-21 21:54   ` Andy Lutomirski
2018-09-22  9:58   ` [tip:x86/cpu] x86/CPU: Change query logic so CPUID " tip-bot for Matthew Whitehead

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