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Date: Thu, 31 Mar 2011 02:03:19 -0400
From: Len Brown <lenb@...nel.org>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
Len Brown <len.brown@...el.com>
Subject: [PATCH 4/9] x86 idle floppy: delete disable_hlt()/enable_hlt()
From: Len Brown <len.brown@...el.com>
The X86_32-only disable_hlt/enable_hlt mechanism was used
by the 32-bit floppy driver. Its effect was to replace
the use of the HLT instruction inside default_idle() with
cpu_relax().
Unlcear why this workaround was ever needed, it was commented:
floppy.c said:
"disable hlt during certain critical i/o operations"
x86/kernel/process.c said:
"This halt magic was a workaround for ancient floppy DMA
wreckage. It should be safe to remove."
So remove it, as it allows us to simplify the x86 idle code.
Signed-off-by: Len Brown <len.brown@...el.com>
---
arch/x86/include/asm/system.h | 7 -------
arch/x86/kernel/process.c | 24 ------------------------
drivers/block/floppy.c | 35 -----------------------------------
3 files changed, 0 insertions(+), 66 deletions(-)
diff --git a/arch/x86/include/asm/system.h b/arch/x86/include/asm/system.h
index 33ecc3e..013dd42 100644
--- a/arch/x86/include/asm/system.h
+++ b/arch/x86/include/asm/system.h
@@ -93,10 +93,6 @@ do { \
"memory"); \
} while (0)
-/*
- * disable hlt during certain critical i/o operations
- */
-#define HAVE_DISABLE_HLT
#else
#define __SAVE(reg, offset) "movq %%" #reg ",(14-" #offset ")*8(%%rsp)\n\t"
#define __RESTORE(reg, offset) "movq (14-" #offset ")*8(%%rsp),%%" #reg "\n\t"
@@ -337,9 +333,6 @@ static inline void clflush(volatile void *__p)
#define nop() asm volatile ("nop")
-void disable_hlt(void);
-void enable_hlt(void);
-
void cpu_idle_wait(void);
extern unsigned long arch_align_stack(unsigned long sp);
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index cd461c3..8688ade 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -342,34 +342,10 @@ EXPORT_SYMBOL(boot_option_idle_override);
void (*pm_idle)(void);
EXPORT_SYMBOL(pm_idle);
-#ifdef CONFIG_X86_32
-/*
- * This halt magic was a workaround for ancient floppy DMA
- * wreckage. It should be safe to remove.
- */
-static int hlt_counter;
-void disable_hlt(void)
-{
- hlt_counter++;
-}
-EXPORT_SYMBOL(disable_hlt);
-
-void enable_hlt(void)
-{
- hlt_counter--;
-}
-EXPORT_SYMBOL(enable_hlt);
-
-static inline int hlt_use_halt(void)
-{
- return (!hlt_counter);
-}
-#else
static inline int hlt_use_halt(void)
{
return 1;
}
-#endif
/*
* We use this if we don't have any better
diff --git a/drivers/block/floppy.c b/drivers/block/floppy.c
index 77fc76f..9a4e006 100644
--- a/drivers/block/floppy.c
+++ b/drivers/block/floppy.c
@@ -1032,36 +1032,6 @@ static int fd_wait_for_completion(unsigned long delay, timeout_fn function)
return 0;
}
-static DEFINE_SPINLOCK(floppy_hlt_lock);
-static int hlt_disabled;
-static void floppy_disable_hlt(void)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&floppy_hlt_lock, flags);
- if (!hlt_disabled) {
- hlt_disabled = 1;
-#ifdef HAVE_DISABLE_HLT
- disable_hlt();
-#endif
- }
- spin_unlock_irqrestore(&floppy_hlt_lock, flags);
-}
-
-static void floppy_enable_hlt(void)
-{
- unsigned long flags;
-
- spin_lock_irqsave(&floppy_hlt_lock, flags);
- if (hlt_disabled) {
- hlt_disabled = 0;
-#ifdef HAVE_DISABLE_HLT
- enable_hlt();
-#endif
- }
- spin_unlock_irqrestore(&floppy_hlt_lock, flags);
-}
-
static void setup_DMA(void)
{
unsigned long f;
@@ -1106,7 +1076,6 @@ static void setup_DMA(void)
fd_enable_dma();
release_dma_lock(f);
#endif
- floppy_disable_hlt();
}
static void show_floppy(void);
@@ -1708,7 +1677,6 @@ irqreturn_t floppy_interrupt(int irq, void *dev_id)
fd_disable_dma();
release_dma_lock(f);
- floppy_enable_hlt();
do_floppy = NULL;
if (fdc >= N_FDC || FDCS->address == -1) {
/* we don't even know which FDC is the culprit */
@@ -1857,8 +1825,6 @@ static void floppy_shutdown(unsigned long data)
show_floppy();
cancel_activity();
- floppy_enable_hlt();
-
flags = claim_dma_lock();
fd_disable_dma();
release_dma_lock(flags);
@@ -4503,7 +4469,6 @@ static void floppy_release_irq_and_dma(void)
#if N_FDC > 1
set_dor(1, ~8, 0);
#endif
- floppy_enable_hlt();
if (floppy_track_buffer && max_buffer_sectors) {
tmpsize = max_buffer_sectors * 1024;
--
1.7.4.2.406.gbe91
--
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