From: Jani Nikula <jani.nikula@linux.intel.com>
To: Matt Roper <matthew.d.roper@intel.com>,
Thomas Gummerer <t.gummerer@gmail.com>
Cc: dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org,
linux-kernel@vger.kernel.org, David Airlie <airlied@linux.ie>,
Daniel Vetter <daniel.vetter@intel.com>,
jan@gondor.com, Tvrtko Ursulin <tvrtko.ursulin@intel.com>,
Michael Leuchtenburg <michael@slashhome.org>
Subject: Re: [PATCH v2] drm/i915: fix screen flickering
Date: Tue, 19 May 2015 10:37:14 +0300 [thread overview]
Message-ID: <87k2w5kogl.fsf@intel.com> (raw)
In-Reply-To: <20150514142836.GE25648@intel.com>
On Thu, 14 May 2015, Matt Roper <matthew.d.roper@intel.com> wrote:
> On Thu, May 14, 2015 at 09:16:39AM +0200, Thomas Gummerer wrote:
>> Commit c9f038a1a592 ("drm/i915: Don't assume primary & cursor are
>> always on for wm calculation (v4)") fixes a null pointer dereference.
>> Setting the primary and cursor panes to false in
>> ilk_compute_wm_parameters to false does however give the following
>> errors in the kernel log and causes the screen to flicker.
>>
>> [ 101.133716] [drm:intel_set_cpu_fifo_underrun_reporting [i915]]
>> *ERROR* uncleared fifo underrun on pipe A
>> [ 101.133725] [drm:intel_cpu_fifo_underrun_irq_handler [i915]]
>> *ERROR* CPU pipe A FIFO underrun
>>
>> Always setting the panes to enabled fixes this error.
>>
>> Helped-by: Matt Roper <matthew.d.roper@intel.com>
>> Signed-off-by: Thomas Gummerer <t.gummerer@gmail.com>
>
> Seems like a reasonable short-term workaround and returns us to how the
> code used to behaves.
>
> Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Pushed to drm-intel-fixes, thanks for the patch and review.
BR,
Jani.
>
>> ---
>>
>> > Sorry, I missed your patch when you first sent it. That type of fix
>> > looks like an okay workaround while we do a more in-depth rework of the
>> > watermark system. However I think your patch could cause a crash if we
>> > disable the primary plane via the universal plane interface; if we do
>> > that, p->pri.bytes_per_pixel is set to 0, but since we're now pretending
>> > the primary plane is always enabled, ilk_wm_fbc() can eventually get
>> > called and use that 0 in the denominator of a division operation.
>> >
>> > If you just squash the following change into your patch, I think it should be
>> > safe:
>> > [...]
>>
>> Thank you very much for the suggestion, here is an updated version of the
>> patch.
>>
>> drivers/gpu/drm/i915/intel_pm.c | 24 +++++++++++-------------
>> 1 file changed, 11 insertions(+), 13 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index fa4ccb3..555b896 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -2045,22 +2045,20 @@ static void ilk_compute_wm_parameters(struct drm_crtc *crtc,
>> p->pipe_htotal = intel_crtc->config->base.adjusted_mode.crtc_htotal;
>> p->pixel_rate = ilk_pipe_pixel_rate(dev, crtc);
>>
>> - if (crtc->primary->state->fb) {
>> - p->pri.enabled = true;
>> + if (crtc->primary->state->fb)
>> p->pri.bytes_per_pixel =
>> crtc->primary->state->fb->bits_per_pixel / 8;
>> - } else {
>> - p->pri.enabled = false;
>> - p->pri.bytes_per_pixel = 0;
>> - }
>> + else
>> + p->pri.bytes_per_pixel = 4;
>> +
>> + p->cur.bytes_per_pixel = 4;
>> + /*
>> + * TODO: for now, assume primary and cursor planes are always enabled.
>> + * Setting them to false makes the screen flicker.
>> + */
>> + p->pri.enabled = true;
>> + p->cur.enabled = true;
>>
>> - if (crtc->cursor->state->fb) {
>> - p->cur.enabled = true;
>> - p->cur.bytes_per_pixel = 4;
>> - } else {
>> - p->cur.enabled = false;
>> - p->cur.bytes_per_pixel = 0;
>> - }
>> p->pri.horiz_pixels = intel_crtc->config->pipe_src_w;
>> p->cur.horiz_pixels = intel_crtc->base.cursor->state->crtc_w;
>>
>> --
>> 2.4.0.184.g8e1974e
>>
>
> --
> Matt Roper
> Graphics Software Engineer
> IoTG Platform Enabling & Development
> Intel Corporation
> (916) 356-2795
--
Jani Nikula, Intel Open Source Technology Center
prev parent reply other threads:[~2015-05-19 7:35 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-12 19:54 [BUG/REGRESSION] Screen flickering Thomas Gummerer
2015-05-13 9:14 ` Jani Nikula
2015-05-13 9:53 ` Jan Niehusmann
2015-05-13 10:32 ` Sudip Mukherjee
2015-05-13 11:10 ` Jan Niehusmann
2015-05-13 11:28 ` Sudip Mukherjee
2015-05-13 11:27 ` Thomas Gummerer
2015-05-13 11:34 ` Sudip Mukherjee
2015-05-13 11:23 ` Thomas Gummerer
2015-05-14 3:21 ` Matt Roper
2015-05-14 7:16 ` [PATCH v2] drm/i915: fix screen flickering Thomas Gummerer
2015-05-14 14:28 ` Matt Roper
2015-05-19 7:37 ` Jani Nikula [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k2w5kogl.fsf@intel.com \
--to=jani.nikula@linux.intel.com \
--cc=airlied@linux.ie \
--cc=daniel.vetter@intel.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=intel-gfx@lists.freedesktop.org \
--cc=jan@gondor.com \
--cc=linux-kernel@vger.kernel.org \
--cc=matthew.d.roper@intel.com \
--cc=michael@slashhome.org \
--cc=t.gummerer@gmail.com \
--cc=tvrtko.ursulin@intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).