From: Ben Widawsky <benjamin.widawsky@intel.com>
To: Ben Widawsky <ben@bwidawsk.net>
Cc: intel-gfx@lists.freedesktop.org, miku@iki.fi, mika.kuoppala@intel.com
Subject: Re: [PATCH 1/5] drm/i915: Fix forcewake counts for gen8
Date: Fri, 21 Feb 2014 11:42:00 -0800 [thread overview]
Message-ID: <20140221194200.GB1073@intel.com> (raw)
In-Reply-To: <20140221193847.GA7594@bwidawsk.net>
On Fri, Feb 21, 2014 at 11:38:48AM -0800, Ben Widawsky wrote:
> On Fri, Feb 21, 2014 at 05:31:59PM +0200, mika.kuoppala@intel.com wrote:
> > From: Mika Kuoppala <mika.kuoppala@intel.com>
> >
> > Sometimes generic driver code gets forcewake explicitly by
> > gen6_gt_force_wake_get(), which check forcewake_count before accessing
> > hardware. However the register access with gen8_write function access
> > low level hw accessors directly, ignoring the forcewake_count. This
> > leads to nested forcewake get from hardware, in ring init and possibly
> > elsewhere, causing forcewake ack clear errors and/or hangs.
> >
> > Fix this by checking the forcewake count also in gen8_write
> >
> > v2: Read side doesn't care about shadowed registers,
> > Remove __needs_put funkiness from gen8_write. (Ville)
> > Improved commit message.
> >
> > References: https://bugs.freedesktop.org/show_bug.cgi?id=74007
> > Cc: Ben Widawsky <benjamin.widawsky@intel.com>
> > Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
> > Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
>
> For those concerned with the performance implication of the extra if
> (if anyone at all cares, it's Chris) - I suppose we could also just add
> the lock to gen6_gt_force_wake_get/put.
>
> [snip]
I should have also said, we have very few cases where it's actually a
problem (ie. not just done at init). And in fact, I am wondering now how
one could hit this at all without enabling rps.
--
Ben Widawsky, Intel Open Source Technology Center
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next prev parent reply other threads:[~2014-02-21 19:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-21 15:31 [PATCH 0/5] bdw forcewake fixes mika.kuoppala
2014-02-21 15:31 ` [PATCH 1/5] drm/i915: Fix forcewake counts for gen8 mika.kuoppala
2014-02-21 19:38 ` Ben Widawsky
2014-02-21 19:42 ` Ben Widawsky [this message]
2014-02-21 19:54 ` Chris Wilson
2014-02-24 11:27 ` Ville Syrjälä
2014-02-24 20:29 ` Ben Widawsky
2014-02-21 15:32 ` [PATCH 2/5] drm/i915: Do forcewake reset on gen8 mika.kuoppala
2014-02-21 15:32 ` [PATCH 3/5] drm/i915: Don't access fifodbg registers " mika.kuoppala
2014-02-21 15:36 ` Chris Wilson
2014-02-21 16:47 ` Mika Kuoppala
2014-02-21 15:32 ` [PATCH 4/5] drm/i915: Always set fifo count to zero in gen6_reset mika.kuoppala
2014-02-21 15:32 ` [PATCH 5/5] drm/i915: No need to put forcewake after a reset mika.kuoppala
2014-03-05 14:58 ` Daniel Vetter
2014-03-05 16:11 ` Mika Kuoppala
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