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From: Brian Masney <masneyb@onstation.org>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Rob Clark <robdclark@gmail.com>, Sean Paul <sean@poorly.run>,
	"open list:DRM PANEL DRIVERS" <dri-devel@lists.freedesktop.org>,
	MSM <linux-arm-msm@vger.kernel.org>,
	freedreno@lists.freedesktop.org, Dave Airlie <airlied@linux.ie>,
	Daniel Vetter <daniel@ffwll.ch>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Jonathan Marek <jonathan@marek.ca>, Rob Herring <robh@kernel.org>
Subject: Re: [PATCH RFC v2 0/6] ARM: qcom: initial Nexus 5 display support
Date: Wed, 29 May 2019 05:41:52 -0400	[thread overview]
Message-ID: <20190529094152.GB13436@basecamp> (raw)
In-Reply-To: <CACRpkdZu5KxKTMqAM5rueWbrXbfPNorOOerezCAA3vgAR6cD5g@mail.gmail.com>

On Wed, May 29, 2019 at 08:23:17AM +0200, Linus Walleij wrote:
> On Wed, May 29, 2019 at 3:17 AM Brian Masney <masneyb@onstation.org> wrote:
> 
> > It's in low speed mode but its usable.
> 
> How low speed is that?

I don't have a number but my test with 4.17 is to run
'cat /etc/passwd > /dev/tty1' over a serial cable. The first 2-3 calls
will fill up the screen and the file contents appear to show up on the
screen immediately to the human eye. The next time that I run it
requires scrolling the entire console and there is a small fraction of
a second where I see the entire framebuffer contents scroll up. I
don't have a graphics background, but I believe that this is the
tearing effect that I'm seeing based on what I've read. I believe that
disp-te-gpios can be used to mitigate this tearing effect. I have a few
questions about this later once we get the basic display working.

> > I assume that it's related to the
> > vblank events not working properly?
> 
> They are only waiting for 50 ms before timing out, I raised it
> to 100ms in the -next kernel. I'm still suspicious about this
> even though I think you said this was not the problem.
> 
> For a command mode panel in LP mode it will nevertheless
> be more than 100ms for sure, the update is visible to the
> naked eye.
> 
> Raise it to 10000 ms or something and see what happens.
> drivers/gpu/drm/drm_atomic_helper.c:
>  msecs_to_jiffies(50)

I previously raised those timeouts as high as 5 seconds and it still
has the same issue. Writing to /dev/tty1 can take anywhere between a few
seconds to 30 seconds or more.

Brian

      reply	other threads:[~2019-05-29  9:41 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-09  2:03 Brian Masney
2019-05-09  2:03 ` [PATCH v2 1/6] drm: msm: remove resv fields from msm_gem_object struct Brian Masney
2019-05-13 20:32   ` Bjorn Andersson
2019-05-13 22:25     ` Brian Masney
2019-05-09  2:03 ` [PATCH RFC v2 2/6] drm: msm: add dirty framebuffer helper Brian Masney
2019-05-09  2:03 ` [PATCH v2 3/6] ARM: qcom_defconfig: add display-related options Brian Masney
2019-05-09  2:03 ` [PATCH v2 4/6] ARM: dts: msm8974: add display support Brian Masney
2019-05-09  2:03 ` [PATCH v2 5/6] ARM: dts: qcom: msm8974-hammerhead: add support for backlight Brian Masney
2019-05-09  2:03 ` [PATCH v2 6/6] ARM: dts: qcom: msm8974-hammerhead: add support for display Brian Masney
2019-05-09  2:06 ` [PATCH RFC v2 0/6] ARM: qcom: initial Nexus 5 display support Brian Masney
2019-05-28 13:46 ` Linus Walleij
2019-05-29  1:17   ` Brian Masney
2019-05-29  1:32     ` [Freedreno] " Jeffrey Hugo
2019-05-29  1:37       ` Brian Masney
2019-05-29  1:42         ` Jeffrey Hugo
2019-05-29  2:46           ` Brian Masney
     [not found]             ` <CAOCk7NpC93ACr4jFm7SBOKSvFJSDhq2byX6BAYPX29BuYEkWnQ@mail.gmail.com>
2019-05-29 10:28               ` Brian Masney
2019-05-29 14:41                 ` Jeffrey Hugo
2019-05-29 19:30                   ` Brian Masney
2019-05-29 19:58                     ` Jeffrey Hugo
2019-05-29 21:54                       ` Brian Masney
2019-05-29  2:14     ` Rob Clark
2019-05-29  2:24       ` [Freedreno] " Jeffrey Hugo
2019-05-29  6:23     ` Linus Walleij
2019-05-29  9:41       ` Brian Masney [this message]

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