On 12/21/2015 05:39 PM, Daniel Vetter wrote:
On Fri, Dec 18, 2015 at 07:24:19AM -0800, Matt Roper wrote:
On Fri, Dec 18, 2015 at 07:14:17AM -0800, Matt Roper wrote:
On Fri, Dec 18, 2015 at 05:10:12PM +0200, Ville Syrjälä wrote:
On Fri, Dec 18, 2015 at 06:58:58AM -0800, Matt Roper wrote:
On Fri, Dec 18, 2015 at 12:35:47PM +0200, Ville Syrjälä wrote:
On Wed, Dec 16, 2015 at 07:06:20PM -0800, Radhakrishna Sripada wrote:
Original value of 32 blocks is not sufficient when using cursor size of
256x256 causing FIFO underruns when the reworked wm
caluclations in
commit 024c9045221fe45482863c47c4b4c47d37f97cbf
Author: Matt Roper <matthew.d.roper@xxxxxxxxx>
Date: Thu Sep 24 15:53:11 2015 -0700
drm/i915/skl: Eliminate usage of pipe_wm_parameters from SKL-style WM (v4)
Well that commit is obviously incorrect. It's now using the pipe src
width as the plane width for all planes.
Yeah, we already noted that bug in another email thread, but decided
that it was unrelated to the problems Radhakrishna is facing.
Radhakrishna is only using a cursor (which doesn't use that buggy
function)
Pop quiz: what does it use then?
All non-cursor planes (i.e., primary+sprite). Cursors use a fixed DDB
allocation (currently 32 blocks as suggested by bspec, but
Radhakrishna's testing has found this to be too small, so his patch here
is bumping that number up.
To elaborate on this some more, we have some suspicions about why the
bspec-suggested 32 blocks might not be enough. There's some new
workaround information in the bspec about sometimes needing to disable
the system agent (SAGV) on non-BXT gen9, depending on the configuration
and that's not something that's been implemented in our driver code yet.
There's also another new workaround that checks raw system memory
bandwidth and adjusts watermark programming that hasn't been implemented
yet either. It could be that one of those two missing workarounds is
the true culprit, but Radhakrishna's patch here looks like a reasonable
short-term workaround; my main worry is that if he needs to bump the
hardcoded 32 up to to 52 for the single pipe case, he might also need to
bump the hardcoded 8 up as well for the multi-pipe case; I don't think
anyone has tested that yet (and this seems to be a SKL-specific problem,
so I can't reproduce it on my BXT).
This needs at least a very big comment that we're just hacking around with
duct-tape. Also allocating DDB shouldn't matter for correctness, as long
as we compute the WM values correctly. I wonder how this fixes anything
really (except making it a bit harder to hit perhaps due to the enlarged
buffering it affords for the cursor).
Agree Daniel, but in our detailed testing this is found to have fixed
reliably all known flickers. I recommend to have a detailed comment and
*put* the duct-tape. I can have a rerun of detailed tests again to
ensure that its indeed fixing everything.
Imo better to just implement the other workarounds first, then see what's
left.
I know there are few known workarounds pending. Lets continue
implementing them and more. But with Matt's patch not fixing the issue,
lets take this as an immediate short term fix and come back to remove
the duct-tape when we have correct fix.
Regards
Shobhit
-Daniel
Matt
Primary and sprite planes are supposed to divide up the remaining blocks
proportional to their size, but the bug here causes them to all be
considered full-screen size. If you're not actually using sprites and
not windowing your primary plane, then the bug has no effect (which is
probably why we didn't already catch and fix it). If you do use a
sprite plane or window your primary plane, your proportions are probably
wrong and you get non-optimal settings, although even then you usually
won't have actual problems.
Matt
and a full-screen primary plane, so the numbers don't actually
change (for his use case).
Of course that bug is still worth fixing too; I was planning on writing
up a patch for it later today.
Matt
are used. Increasing the number of blocks to 52 to make cursor plane tolerate
SAGV block time for the maximum possible cursor size.
Signed-off-by: Radhakrishna Sripada <radhakrishna.sripada@xxxxxxxxx>
Signed-off-by: Kalyan Kondapally <kalyan.kondapally@xxxxxxxxx>
---
drivers/gpu/drm/i915/intel_pm.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index d385d99..137fb68 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -2802,7 +2802,7 @@ skl_ddb_get_pipe_allocation_limits(struct drm_device *dev,
static unsigned int skl_cursor_allocation(const struct intel_wm_config *config)
{
if (config->num_pipes_active == 1)
- return 32;
+ return 52;
return 8;
}
--
1.9.1
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--
Ville Syrjälä
Intel OTC
--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
--
Ville Syrjälä
Intel OTC
--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
--
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795
_______________________________________________
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