i8253 locking and PC speaker on non-{mips,x86}

i8253 locking and PC speaker on non-{mips,x86}

[Ralf Baechle]

No longer terribly relevant these days but ...

drivers/input/misc/pcspkr.c:

#if defined(CONFIG_MIPS) || defined(CONFIG_X86)
/* Use the global PIT lock ! */
#include <asm/i8253.h>
#else
#include <asm/8253pit.h>
static DEFINE_RAW_SPINLOCK(i8253_lock);
#endif

sound/drivers/pcsp/pcsp.h:

#if defined(CONFIG_MIPS) || defined(CONFIG_X86)
/* Use the global PIT lock ! */
#include <asm/i8253.h>
#else
#include <asm/8253pit.h>
static DEFINE_RAW_SPINLOCK(i8253_lock);

$ git grep -F pcsp.h sound/drivers/pcsp
sound/drivers/pcsp/pcsp.c:#include "pcsp.h"
sound/drivers/pcsp/pcsp_input.c:#include "pcsp.h"
sound/drivers/pcsp/pcsp_lib.c:#include "pcsp.h"
sound/drivers/pcsp/pcsp_mixer.c:#include "pcsp.h"
$ git grep -w i8253_lock sound/drivers/pcsp/
sound/drivers/pcsp/pcsp.h:static DEFINE_RAW_SPINLOCK(i8253_lock);
sound/drivers/pcsp/pcsp_input.c:        raw_spin_lock_irqsave(&i8253_lock, flags
sound/drivers/pcsp/pcsp_input.c:        raw_spin_unlock_irqrestore(&i8253_lock, 
sound/drivers/pcsp/pcsp_lib.c:          raw_spin_lock_irqsave(&i8253_lock, flags
sound/drivers/pcsp/pcsp_lib.c:          raw_spin_unlock_irqrestore(&i8253_lock, 
sound/drivers/pcsp/pcsp_lib.c:  raw_spin_lock(&i8253_lock);
sound/drivers/pcsp/pcsp_lib.c:  raw_spin_unlock(&i8253_lock);
sound/drivers/pcsp/pcsp_lib.c:  raw_spin_lock(&i8253_lock);
sound/drivers/pcsp/pcsp_lib.c:  raw_spin_unlock(&i8253_lock);

Locks are great, everybody should have their own lock!

$ find . -name 8253pit.h
./arch/powerpc/include/asm/8253pit.h
./arch/alpha/include/asm/8253pit.h
$ cat arch/*/include/asm/8253pit.h
/*
 * 8253/8254 Programmable Interval Timer
 */
/*
 * 8253/8254 Programmable Interval Timer
 */
$

Eh...

$ git grep -w PCSPKR_PLATFORM 
arch/mips/Kconfig:      select PCSPKR_PLATFORM
arch/mips/Kconfig:      select PCSPKR_PLATFORM
arch/mips/Kconfig:      select PCSPKR_PLATFORM
arch/powerpc/platforms/amigaone/Kconfig:        select PCSPKR_PLATFORM
drivers/input/misc/Kconfig:     depends on PCSPKR_PLATFORM
init/Kconfig:config PCSPKR_PLATFORM
sound/drivers/Kconfig:  depends on PCSPKR_PLATFORM && X86 && HIGH_RES_TIMERS

So works on MIPS and x86.  Compiles on PowerPC but locking is wrong.  On
Alpha can't even be selected though it sees otherwise right except the
locking and even worse for the rest.

  Ralf

Re: i8253 locking and PC speaker on non-{mips,x86}

[Takashi Iwai]

At Sat, 28 May 2011 12:21:20 +0100,
Ralf Baechle wrote:
> 
> No longer terribly relevant these days but ...
> 
> drivers/input/misc/pcspkr.c:
> 
> #if defined(CONFIG_MIPS) || defined(CONFIG_X86)
> /* Use the global PIT lock ! */
> #include <asm/i8253.h>
> #else
> #include <asm/8253pit.h>
> static DEFINE_RAW_SPINLOCK(i8253_lock);
> #endif
> 
> sound/drivers/pcsp/pcsp.h:
> 
> #if defined(CONFIG_MIPS) || defined(CONFIG_X86)
> /* Use the global PIT lock ! */
> #include <asm/i8253.h>
> #else
> #include <asm/8253pit.h>
> static DEFINE_RAW_SPINLOCK(i8253_lock);
> 
> $ git grep -F pcsp.h sound/drivers/pcsp
> sound/drivers/pcsp/pcsp.c:#include "pcsp.h"
> sound/drivers/pcsp/pcsp_input.c:#include "pcsp.h"
> sound/drivers/pcsp/pcsp_lib.c:#include "pcsp.h"
> sound/drivers/pcsp/pcsp_mixer.c:#include "pcsp.h"
> $ git grep -w i8253_lock sound/drivers/pcsp/
> sound/drivers/pcsp/pcsp.h:static DEFINE_RAW_SPINLOCK(i8253_lock);
> sound/drivers/pcsp/pcsp_input.c:        raw_spin_lock_irqsave(&i8253_lock, flags
> sound/drivers/pcsp/pcsp_input.c:        raw_spin_unlock_irqrestore(&i8253_lock, 
> sound/drivers/pcsp/pcsp_lib.c:          raw_spin_lock_irqsave(&i8253_lock, flags
> sound/drivers/pcsp/pcsp_lib.c:          raw_spin_unlock_irqrestore(&i8253_lock, 
> sound/drivers/pcsp/pcsp_lib.c:  raw_spin_lock(&i8253_lock);
> sound/drivers/pcsp/pcsp_lib.c:  raw_spin_unlock(&i8253_lock);
> sound/drivers/pcsp/pcsp_lib.c:  raw_spin_lock(&i8253_lock);
> sound/drivers/pcsp/pcsp_lib.c:  raw_spin_unlock(&i8253_lock);
> 
> Locks are great, everybody should have their own lock!

Yeah, if they were actually built.  But snd-pcsp driver is built only
for x86:

config SND_PCSP
	tristate "PC-Speaker support (READ HELP!)"
	depends on PCSPKR_PLATFORM && X86 && HIGH_RES_TIMERS
	depends on INPUT
	depends on EXPERIMENTAL

So, the current code in sound/drivers/pcsp/pcsp.h is harmless, but
just confusing because of copy-and-paste from
drivers/input/misc/pcspkr.c.
The part for non-x86 should be removed or commented better.


thanks,

Takashi