[Intel-gfx] [PATCH] drm/i915: Fix big cursors on snb

[Daniel Vetter]

Hi Art,

Indeed my patch looks fishy and it's because this isn't the code I've
tested the entire night :(

The one that works simply disables lp1+ wm levels. Which is a bit an
oversized hammer really. Do you have any ideas for w/a or smaller
tricks I could try? I did try just blantantly multiplying wm levels a
bit but that didn't help. At least not the few things I've tried.

Still only seen this on snb thus far.

Thanks, Daniel


On Mon, Mar 2, 2015 at 8:39 PM, Runyan, Arthur J
<arthur.j.runyan at intel.com> wrote:
> I think your ilk_wm_method2 is busted.  Method 2 should always give more than one full line, making this 1 line redundant.
>
>
> -----Original Message-----
> From: Daniel Vetter [mailto:daniel.vetter at ffwll.ch]
> Sent: Monday, March 02, 2015 9:09 AM
> To: Intel Graphics Development; Runyan, Arthur J
> Cc: Daniel Vetter; Ville Syrjälä; Roper, Matthew D; Paulo Zanoni; Vetter, Daniel
> Subject: Re: [PATCH] drm/i915: Fix big cursors on snb
>
> Forgotten to cc Art as fyi.
> -Daniel
>
> On Mon, Mar 2, 2015 at 5:35 PM, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
>> My snb seemed somewhat unhappy with 256x256 cursors and failed all the
>> relevant kms_cursor_crc subtests sporadically, including logging cpu
>> fifo underruns. Smaller cursor work perfectly with a failure rate at
>> least 1000x less (got bored after running tests for days).
>>
>> After some playing around with impressive hammers Ville suggested to
>> increase the watermarks to at least cover a full cursor line. It seems
>> to work thus far. This means that for lp wms we now required 1/4th of
>> the fifo for 256 wide cursors, and much less on gen7+. Hence fetches
>> should still be nice&big. Therefore I expect very little power impact
>> and decided to just do this everywhere, even though I've only seen
>> this on my snb laptop. Especially since Ville is thinking about
>> similar changes for the gmch wm code. skl separate wm code and also
>> completely new plane hw, so hopefully isn't affected.
>>
>> Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
>> Cc: Matt Roper <matthew.d.roper at intel.com>
>> Cc: Paulo Zanoni <przanoni at gmail.com>
>> Testcase: igt/kms_cursor_crc/*-256x256-*
>> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
>> ---
>>  drivers/gpu/drm/i915/intel_pm.c | 17 ++++++++++++-----
>>  1 file changed, 12 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index 7dcb5b60600b..7e97a30bd6c0 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm[Art]  /i915/intel_pm.c
>> @@ -1449,14 +1449,21 @@ static uint32_t ilk_compute_spr_wm(const struct ilk_pipe_wm_parameters *params,
>>  static uint32_t ilk_compute_cur_wm(const struct ilk_pipe_wm_parameters *params,
>>                                    uint32_t mem_value)
>>  {
>> +       uint32_t line_wm, method2;
>> +
>>         if (!params->active || !params->cur.enabled)
>>                 return 0;
>>
>> -       return ilk_wm_method2(params->pixel_rate,
>> -                             params->pipe_htotal,
>> -                             params->cur.horiz_pixels,
>> -                             params->cur.bytes_per_pixel,
>> -                             mem_value);
>> +       /* HACK: Big cursors tend to underrun, load at least one line. */
>> +       line_wm = params->cur.horiz_pixels * params->cur.bytes_per_pixel / 64;
>> +
>> +       method2 = ilk_wm_method2(params->pixel_rate,
>> +                                params->pipe_htotal,
>> +                                params->cur.horiz_pixels,
>> +                                params->cur.bytes_per_pixel,
>> +                                mem_value);
>> +
>> +       return max(line_wm, method2);
>>  }
>>
>>  /* Only for WM_LP. */
>> --
>> 1.9.3
>>
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch