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From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>,
	intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915/icl: do a posting read after irq install
Date: Wed, 23 Jan 2019 13:59:07 +0200	[thread overview]
Message-ID: <877eevmvp0.fsf@gaia.fi.intel.com> (raw)
In-Reply-To: <154823289585.693.6689251338992129659@skylake-alporthouse-com>

Chris Wilson <chris@chris-wilson.co.uk> writes:

> Quoting Daniele Ceraolo Spurio (2019-01-23 02:32:27)
>> When reading GEN11_GT_INTR_DWx closely after enabling the interrupts
>> in gen11_irq_postinstall, the returned value is garbage. This can
>> cause other parts of the setup code (e.g. gen11_reset_one_iir) to
>> think that there are interrupts to be cleared when there are none.
>> 
>> The garbage value is only seen on the first read done after the enable,
>> so this looks like a posting issue. Adding a posting read after enabling
>> the interrupts does indeed fix the problem.
>> 
>> Note that the posting read has been purposely added outside of
>> gen11_master_intr_enable since the issue has only been observed when the
>> full interrupt setup is performed.
>> 
>> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
>> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
>
> irq regs and flushing stale results (side effect or double buffering? or
> maybe latching?), seem to go hand in hand.
>
> Acked-by: Chris Wilson <chris@chris-wilson.co.uk>

Pushed. Thank you for patch and ack.
-Mika
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      reply	other threads:[~2019-01-23 12:01 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-23  2:32 [PATCH] drm/i915/icl: do a posting read after irq install Daniele Ceraolo Spurio
2019-01-23  3:28 ` Daniele Ceraolo Spurio
2019-01-23 11:40   ` Mika Kuoppala
2019-01-23 18:38     ` Daniele Ceraolo Spurio
2019-01-23  4:52 ` ✓ Fi.CI.BAT: success for " Patchwork
2019-01-23  6:39 ` ✓ Fi.CI.IGT: " Patchwork
2019-01-23  8:41 ` [PATCH] " Chris Wilson
2019-01-23 11:59   ` Mika Kuoppala [this message]

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