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From: Rob Clark <robdclark@chromium.org>
To: Brian Ho <brian@brkho.com>,
	freedreno <freedreno@lists.freedesktop.org>,
	 Rob Clark <robdclark@chromium.org>,
	David Airlie <airlied@linux.ie>,
	 "open list:DRM DRIVER FOR MSM ADRENO GPU"
	<linux-arm-msm@vger.kernel.org>,
	open list <linux-kernel@vger.kernel.org>,
	 "open list:DRM DRIVER FOR MSM ADRENO GPU"
	<dri-devel@lists.freedesktop.org>,
	Rob Clark <robdclark@gmail.com>,  Daniel Vetter <daniel@ffwll.ch>,
	Kristian Kristensen <hoegsberg@chromium.org>,
	Sean Paul <sean@poorly.run>
Subject: Re: [Freedreno] [PATCH 2/2] drm/msm: Add MSM_WAIT_IOVA ioctl
Date: Tue, 14 Jan 2020 08:52:43 -0800	[thread overview]
Message-ID: <CAJs_Fx6AVwA73eN+Rs=GAvBPD1Leq=WKG9w_2hohpzmecK_C_A@mail.gmail.com> (raw)
In-Reply-To: <20200113175148.GC26711@jcrouse1-lnx.qualcomm.com>

On Mon, Jan 13, 2020 at 9:51 AM Jordan Crouse <jcrouse@codeaurora.org> wrote:
>
> On Mon, Jan 13, 2020 at 10:36:05AM -0500, Brian Ho wrote:
> > +
> > +     vaddr = base_vaddr + args->offset;
> > +
> > +     /* Assumes WC mapping */
> > +     ret = wait_event_interruptible_timeout(
> > +                     gpu->event, *vaddr >= args->value, remaining_jiffies);
>
> I feel like a barrier might be needed before checking *vaddr just in case you
> get the interrupt and wake up the queue before the write posts from the
> hardware.
>

if the gpu is doing posted (or cached) writes, I don't think there is
even a CPU side barrier primitive that could wait for that?  I think
we rely on the GPU not interrupting the CPU until the write is posted

BR,
-R
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  parent reply	other threads:[~2020-01-15  8:28 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-13 15:36 [PATCH 0/2] drm/msm: Add the MSM_WAIT_IOVA ioctl Brian Ho
2020-01-13 15:36 ` [PATCH 1/2] drm/msm: Add a GPU-wide wait queue Brian Ho
2020-01-13 17:55   ` [Freedreno] " Jordan Crouse
2020-01-13 18:23     ` Rob Clark
2020-01-13 15:36 ` [PATCH 2/2] drm/msm: Add MSM_WAIT_IOVA ioctl Brian Ho
2020-01-13 16:25   ` Rob Clark
2020-01-13 17:57     ` Kristian Kristensen
2020-01-13 22:55       ` Brian Ho
2020-01-13 23:17         ` Rob Clark
2020-01-14  0:45           ` [Freedreno] " Kristian Høgsberg
2020-01-14 16:40           ` Brian Ho
2020-01-14 16:48             ` Rob Clark
2020-01-14 17:45               ` Brian Ho
2020-01-13 17:51   ` [Freedreno] " Jordan Crouse
2020-01-13 18:21     ` Rob Clark
2020-01-14 16:52     ` Rob Clark [this message]
2020-01-14 17:23       ` Jordan Crouse
2020-01-14 17:30         ` Kristian Kristensen
2020-01-14 18:05           ` Jordan Crouse

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