[Intel-gfx] [RFC 1/4] x86/platform/intel/iosf_mbi: Add a mutex for punit access

[Ville Syrjälä]

On Sun, Jan 01, 2017 at 09:14:00PM +0100, Hans de Goede wrote:
> The punit on baytrail / cherrytrail systems is not only accessed through
> the iosf_mbi functions, but also by the i915 code. Add a mutex to protect
> the punit against simultaneous accesses and 2 functions to lock / unlock
> this mutex.

I'm not sure which part of punit you're actually trying to protect
here. Some specific registers?

> 
> Signed-off-by: Hans de Goede <hdegoede at redhat.com>
> ---
>  arch/x86/include/asm/iosf_mbi.h    | 19 +++++++++++++++++++
>  arch/x86/platform/intel/iosf_mbi.c | 13 +++++++++++++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/arch/x86/include/asm/iosf_mbi.h b/arch/x86/include/asm/iosf_mbi.h
> index b41ee16..02963bd 100644
> --- a/arch/x86/include/asm/iosf_mbi.h
> +++ b/arch/x86/include/asm/iosf_mbi.h
> @@ -88,6 +88,21 @@ int iosf_mbi_write(u8 port, u8 opcode, u32 offset, u32 mdr);
>   */
>  int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask);
>  
> +/**
> + * iosf_mbi_punit_lock() - Lock the punit mutex
> + *
> + * This function must be called before accessing the punit or the pmic, be it
> + * through iosf_mbi_* or through other means.
> + *
> + * This function locks a mutex, as such it may sleep.
> + */
> +void iosf_mbi_punit_lock(void);
> +
> +/**
> + * iosf_mbi_punit_unlock() - Unlock the punit mutex
> + */
> +void iosf_mbi_punit_unlock(void);
> +
>  #else /* CONFIG_IOSF_MBI is not enabled */
>  static inline
>  bool iosf_mbi_available(void)
> @@ -115,6 +130,10 @@ int iosf_mbi_modify(u8 port, u8 opcode, u32 offset, u32 mdr, u32 mask)
>  	WARN(1, "IOSF_MBI driver not available");
>  	return -EPERM;
>  }
> +
> +static inline void iosf_mbi_punit_lock(void) {}
> +static inline void iosf_mbi_punit_unlock(void) {}
> +
>  #endif /* CONFIG_IOSF_MBI */
>  
>  #endif /* IOSF_MBI_SYMS_H */
> diff --git a/arch/x86/platform/intel/iosf_mbi.c b/arch/x86/platform/intel/iosf_mbi.c
> index edf2c54..75d8135 100644
> --- a/arch/x86/platform/intel/iosf_mbi.c
> +++ b/arch/x86/platform/intel/iosf_mbi.c
> @@ -34,6 +34,7 @@
>  
>  static struct pci_dev *mbi_pdev;
>  static DEFINE_SPINLOCK(iosf_mbi_lock);
> +static DEFINE_MUTEX(iosf_mbi_punit_mutex);
>  
>  static inline u32 iosf_mbi_form_mcr(u8 op, u8 port, u8 offset)
>  {
> @@ -190,6 +191,18 @@ bool iosf_mbi_available(void)
>  }
>  EXPORT_SYMBOL(iosf_mbi_available);
>  
> +void iosf_mbi_punit_lock(void)
> +{
> +	mutex_lock(&iosf_mbi_punit_mutex);
> +}
> +EXPORT_SYMBOL(iosf_mbi_punit_lock);
> +
> +void iosf_mbi_punit_unlock(void)
> +{
> +	mutex_unlock(&iosf_mbi_punit_mutex);
> +}
> +EXPORT_SYMBOL(iosf_mbi_punit_unlock);
> +
>  #ifdef CONFIG_IOSF_MBI_DEBUG
>  static u32	dbg_mdr;
>  static u32	dbg_mcr;
> -- 
> 2.9.3

-- 
Ville Syrjälä
Intel OTC