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From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>, Len Brown <lenb@kernel.org>,
	Jani Nikula <jani.nikula@linux.intel.com>,
	"russianneuromancer @ ya . ru" <russianneuromancer@ya.ru>,
	linux-i2c@vger.kernel.org,
	intel-gfx <intel-gfx@lists.freedesktop.org>
Subject: Re: [RFC 1/4] x86/platform/intel/iosf_mbi: Add a mutex for punit access
Date: Fri, 13 Jan 2017 14:20:16 +0200	[thread overview]
Message-ID: <20170113122016.GI31595@intel.com> (raw)
In-Reply-To: <d504f816-96f6-a745-e73c-eb0ea1bd8620@linux.intel.com>

On Fri, Jan 13, 2017 at 01:12:15PM +0200, Jarkko Nikula wrote:
> On 01/13/2017 12:51 PM, Ville Syrjälä wrote:
> > On Fri, Jan 13, 2017 at 12:34:54PM +0200, Jarkko Nikula wrote:
> >> On 01/13/2017 11:26 AM, Ville Syrjälä wrote:
> >>> It also feels quite hand wavy since the punit could do whatever at
> >>> any time AFAIK. Eg. if there's some thermal event or something the
> >>> punit might kick into action. So trying to protect this from the OS
> >>> side might not be able to avoid these problems entirely. It feels like
> >>> there really should be some kind of shared hardware/firmware mutex
> >>> with the punit to arbitrate access to the i2c bus.
> >>>
> >> There is an HW semaphore for I2C access. It is implemented in
> >> drivers/i2c/busses/i2c-designware-baytrail.c and another set from Hans
> >> is adding support for Cherrytrail into it.
> >
> > Then why do we need anything else?
> >
>  From this patch: "The punit on baytrail / cherrytrail systems is not 
> only accessed through the iosf_mbi functions, but also by the i915 code."

I don't see how that's relevant at all. Multiple things accessing the
punit concurrently should be perfectly fine as long as they don't frob
the same registers.

-- 
Ville Syrjälä
Intel OTC

  reply	other threads:[~2017-01-13 12:20 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-01-01 20:13 [RFC 0/4] Coordinate pmic i2c bus and i915 punit accesses Hans de Goede
2017-01-01 20:14 ` [RFC 1/4] x86/platform/intel/iosf_mbi: Add a mutex for punit access Hans de Goede
2017-01-02 14:12   ` Ville Syrjälä
2017-01-02 14:21     ` Hans de Goede
2017-01-13  9:26       ` Ville Syrjälä
2017-01-13 10:34         ` Jarkko Nikula
2017-01-13 10:51           ` Ville Syrjälä
2017-01-13 11:12             ` Jarkko Nikula
2017-01-13 12:20               ` Ville Syrjälä [this message]
2017-01-13 16:06         ` Hans de Goede
2017-01-13 16:30           ` Ville Syrjälä
2017-01-15 11:10             ` Hans de Goede
2017-01-01 20:14 ` [RFC 2/4] i2c: designware-baytrail: Take punit lock on bus acquire Hans de Goede
2017-01-01 20:14 ` [RFC 3/4] drm/i915: valleyview: Make intel_set_rps get FORCEWAKE_MEDIA Hans de Goede
2017-01-01 20:24   ` [Intel-gfx] " Chris Wilson
2017-01-01 20:48     ` Hans de Goede
2017-01-02 11:37       ` [Intel-gfx] " Chris Wilson
2017-01-02 12:40         ` Hans de Goede
2017-01-02 14:10         ` Ville Syrjälä
2017-01-02 14:21           ` Chris Wilson
2017-01-02 14:40             ` Ville Syrjälä
2017-01-02 14:53               ` [Intel-gfx] " Chris Wilson
2017-01-02 15:02                 ` Ville Syrjälä
2017-01-02 15:08                   ` Ville Syrjälä
2017-01-01 20:14 ` [RFC 4/4] drm/i915: valleyview: Take punit lock when modifying punit settings Hans de Goede

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