Op 31-05-17 om 12:42 schreef Mahesh Kumar:
> Hi,
>
>
> On Wednesday 31 May 2017 01:26 PM, Maarten Lankhorst wrote:
>> On some systems there can be a race condition in which no crtc state is
>> added to the first atomic commit. This results in all crtc's having a
>> null DDB allocation, causing a FIFO underrun on any update until the
>> first modeset.
>>
>> Reported-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
>> Inspired-by: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
>> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
>> Fixes: 98d39494d375 ("drm/i915/gen9: Compute DDB allocation at atomic
>> check time (v4)")
>> Cc: <stable@xxxxxxxxxxxxxxx> # v4.8+
>> Cc: Mahesh Kumar <mahesh1.kumar@xxxxxxxxx>
>> Cc: Matt Roper <matthew.d.roper@xxxxxxxxx>
>> ---
>> drivers/gpu/drm/i915/intel_pm.c | 18 ++++++++++++++++++
>> 1 file changed, 18 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
>> index a488e068c3d6..8daa382b47f3 100644
>> --- a/drivers/gpu/drm/i915/intel_pm.c
>> +++ b/drivers/gpu/drm/i915/intel_pm.c
>> @@ -5037,10 +5037,27 @@ skl_compute_wm(struct drm_atomic_state *state)
>> struct drm_crtc_state *cstate;
>> struct intel_atomic_state *intel_state = to_intel_atomic_state(state);
>> struct skl_wm_values *results = &intel_state->wm_results;
>> + struct drm_device *dev = state->dev;
>> struct skl_pipe_wm *pipe_wm;
>> bool changed = false;
>> int ret, i;
>> + if (to_i915(dev)->wm.distrust_bios_wm) {
>> + changed = true;
>> +
>> + /*
>> + * The first commit after driver load must update the ddb
>> + * allocations, so make sure we at least hold a lock to
>> + * inspect the state required for watermark updates.
>> + *
>> + * Below we'll grab the required crtc state.
>> + */
>> + ret = drm_modeset_lock(&dev->mode_config.connection_mutex,
>> + state->acquire_ctx);
> Do we need to get lock here?
> We will anyway go ahead & get the connection_mutex lock during skl_compute_ddb based on distruct_bios_wm flag.
Oh right, missed that one, yeah ignore it. :)
I'll send the original patch again, thanks for catching.
~Maarten