Re: RFC: outb 0x80 in inb_p, outb_p harmful on some modern AMD64 with MCP51 laptops

[Ingo Molnar <mingo@elte.hu>]

* Andi Kleen <andi@firstfloor.org> wrote:

> > Why is TSC significant? udelay() based on bogomips seems to be good 
> > enough...?
> 
> Maybe I'm not sure how accurate it really is on non TSC system. On the 
> other hand it is unclear that the port 80 IO is always the same time 
> so it's probably ok to vary a bit. So most likely going to udelay() 
> unconditionally is fine.

yep, agreed, and have queued up the patch below. I've killed the 
misc_*.c outb_p() uses because they happen before there's an udelay() 
available - but that should be perfectly fine anyway: i dont remember 
any video hardware that needed pauses for cursor updates, i think those 
_p()'s just came in accidentally. (there's hardware that needed _p() for 
other aspects of video such as mode switching - but cursor updates ...)

	Ingo

------------------>
Subject: x86: fix in/out_p delays
From: Ingo Molnar <mingo@elte.hu>

Debugged by David P. Reed <dpreed@reed.com>.

Do not use port 0x80, it can cause crashes, see:

 http://bugzilla.kernel.org/show_bug.cgi?id=6307
 http://bugzilla.kernel.org/show_bug.cgi?id=9511

instead of just removing _p postfixes en masse, lets just first
remove the 0x80 port usage, then remove any unnecessary _p io ops
gradually. It's more debuggable this way.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
 arch/x86/boot/compressed/misc_32.c |    8 ++++----
 arch/x86/boot/compressed/misc_64.c |    8 ++++----
 arch/x86/kernel/quirks.c           |   10 ++++++++++
 include/asm-x86/io_32.h            |    5 +----
 include/asm-x86/io_64.h            |    5 +----
 5 files changed, 20 insertions(+), 16 deletions(-)

Index: linux-x86.q/arch/x86/boot/compressed/misc_32.c
===================================================================
--- linux-x86.q.orig/arch/x86/boot/compressed/misc_32.c
+++ linux-x86.q/arch/x86/boot/compressed/misc_32.c
@@ -276,10 +276,10 @@ static void putstr(const char *s)
 	RM_SCREEN_INFO.orig_y = y;
 
 	pos = (x + cols * y) * 2;	/* Update cursor position */
-	outb_p(14, vidport);
-	outb_p(0xff & (pos >> 9), vidport+1);
-	outb_p(15, vidport);
-	outb_p(0xff & (pos >> 1), vidport+1);
+	outb(14, vidport);
+	outb(0xff & (pos >> 9), vidport+1);
+	outb(15, vidport);
+	outb(0xff & (pos >> 1), vidport+1);
 }
 
 static void* memset(void* s, int c, unsigned n)
Index: linux-x86.q/arch/x86/boot/compressed/misc_64.c
===================================================================
--- linux-x86.q.orig/arch/x86/boot/compressed/misc_64.c
+++ linux-x86.q/arch/x86/boot/compressed/misc_64.c
@@ -275,10 +275,10 @@ static void putstr(const char *s)
 	RM_SCREEN_INFO.orig_y = y;
 
 	pos = (x + cols * y) * 2;	/* Update cursor position */
-	outb_p(14, vidport);
-	outb_p(0xff & (pos >> 9), vidport+1);
-	outb_p(15, vidport);
-	outb_p(0xff & (pos >> 1), vidport+1);
+	outb(14, vidport);
+	outb(0xff & (pos >> 9), vidport+1);
+	outb(15, vidport);
+	outb(0xff & (pos >> 1), vidport+1);
 }
 
 static void* memset(void* s, int c, unsigned n)
Index: linux-x86.q/arch/x86/kernel/quirks.c
===================================================================
--- linux-x86.q.orig/arch/x86/kernel/quirks.c
+++ linux-x86.q/arch/x86/kernel/quirks.c
@@ -3,9 +3,19 @@
  */
 #include <linux/pci.h>
 #include <linux/irq.h>
+#include <linux/delay.h>
 
 #include <asm/hpet.h>
 
+/*
+ * Some legacy devices need delays for IN/OUT sequences. Most are
+ * probably not needed but it's the safest to just do this short delay:
+ */
+void native_io_delay(void)
+{
+	udelay(1);
+}
+
 #if defined(CONFIG_X86_IO_APIC) && defined(CONFIG_SMP) && defined(CONFIG_PCI)
 
 static void __devinit quirk_intel_irqbalance(struct pci_dev *dev)
Index: linux-x86.q/include/asm-x86/io_32.h
===================================================================
--- linux-x86.q.orig/include/asm-x86/io_32.h
+++ linux-x86.q/include/asm-x86/io_32.h
@@ -250,10 +250,7 @@ static inline void flush_write_buffers(v
 
 #endif /* __KERNEL__ */
 
-static inline void native_io_delay(void)
-{
-	asm volatile("outb %%al,$0x80" : : : "memory");
-}
+extern void native_io_delay(void);
 
 #if defined(CONFIG_PARAVIRT)
 #include <asm/paravirt.h>
Index: linux-x86.q/include/asm-x86/io_64.h
===================================================================
--- linux-x86.q.orig/include/asm-x86/io_64.h
+++ linux-x86.q/include/asm-x86/io_64.h
@@ -35,10 +35,7 @@
   *  - Arnaldo Carvalho de Melo <acme@conectiva.com.br>
   */
 
-static inline void native_io_delay(void)
-{
-	asm volatile("outb %%al,$0x80" : : : "memory");
-}
+extern void native_io_delay(void);
 
 #if defined(CONFIG_PARAVIRT)
 #include <asm/paravirt.h>