[Intel-gfx] [PATCH v6 8/8] drm/i915/gen9: WM memory bandwidth related workaround
Lankhorst, Maarten
maarten.lankhorst at intel.com
Tue Nov 29 15:10:37 UTC 2016
Mahesh Kumar schreef op di 29-11-2016 om 19:17 [+0530]:
>
> On Tuesday 29 November 2016 03:16 PM, Lankhorst, Maarten wrote:
> >
> > Mahesh Kumar schreef op di 29-11-2016 om 11:12 [+0530]:
> > >
> > > Hi,
> > >
> > >
> > > On Thursday 24 November 2016 06:21 PM, Lankhorst, Maarten wrote:
> > > >
> > > > Mahesh Kumar schreef op do 24-11-2016 om 09:31 [+0530]:
> > > > >
> > > > > This patch implemnets Workariunds related to display
> > > > > arbitrated
> > > > > memory
> > > > > bandwidth. These WA are applicabe for all gen-9 based
> > > > > platforms.
> > > > >
> > > > > Changes since v1:
> > > > > - Rebase on top of Paulo's patch series
> > > > > Changes since v2:
> > > > > - Address review comments
> > > > > - Rebase/rework as per other patch changes in series
> > > > >
> > > > > Signed-off-by: Mahesh Kumar <mahesh1.kumar at intel.com>
> > > > > ---
> > > > > drivers/gpu/drm/i915/i915_drv.h | 9 +++
> > > > > drivers/gpu/drm/i915/intel_pm.c | 149
> > > > > +++++++++++++++++++++++++++++++++++++---
> > > > > 2 files changed, 149 insertions(+), 9 deletions(-)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/i915_drv.h
> > > > > b/drivers/gpu/drm/i915/i915_drv.h
> > > > > index 4e2f17f..2b673c6 100644
> > > > > --- a/drivers/gpu/drm/i915/i915_drv.h
> > > > > +++ b/drivers/gpu/drm/i915/i915_drv.h
> > > > > @@ -1193,6 +1193,13 @@ enum intel_sbi_destination {
> > > > > SBI_MPHY,
> > > > > };
> > > > >
> > > > > +/* SKL+ Watermark arbitrated display bandwidth Workarounds
> > > > > */
> > > > > +enum watermark_memory_wa {
> > > > > + WATERMARK_WA_NONE,
> > > > > + WATERMARK_WA_X_TILED,
> > > > > + WATERMARK_WA_Y_TILED,
> > > > > +};
> > > > > +
> > > > > #define QUIRK_PIPEA_FORCE (1<<0)
> > > > > #define QUIRK_LVDS_SSC_DISABLE (1<<1)
> > > > > #define QUIRK_INVERT_BRIGHTNESS (1<<2)
> > > > > @@ -1764,6 +1771,8 @@ struct skl_ddb_allocation {
> > > > >
> > > > > struct skl_wm_values {
> > > > > unsigned dirty_pipes;
> > > > > + /* any WaterMark memory workaround Required */
> > > > > + enum watermark_memory_wa mem_wa;
> > > > > struct skl_ddb_allocation ddb;
> > > > > };
> > > > >
> > > > > diff --git a/drivers/gpu/drm/i915/intel_pm.c
> > > > > b/drivers/gpu/drm/i915/intel_pm.c
> > > > > index 3e2dd8f..547bbda 100644
> > > > > --- a/drivers/gpu/drm/i915/intel_pm.c
> > > > > +++ b/drivers/gpu/drm/i915/intel_pm.c
> > > > > @@ -2889,11 +2889,7 @@ skl_wm_plane_id(const struct
> > > > > intel_plane
> > > > > *plane)
> > > > > }
> > > > > }
> > > > >
> > > > > -/*
> > > > > - * FIXME: We still don't have the proper code detect if we
> > > > > need
> > > > > to
> > > > > apply the WA,
> > > > > - * so assume we'll always need it in order to avoid
> > > > > underruns.
> > > > > - */
> > > > > -static bool skl_needs_memory_bw_wa(struct intel_atomic_state
> > > > > *state)
> > > > > +static bool intel_needs_memory_bw_wa(struct
> > > > > intel_atomic_state
> > > > > *state)
> > > > > {
> > > > > struct drm_i915_private *dev_priv = to_i915(state-
> > > > > >
> > > > > > base.dev);
> > > > >
> > > > > @@ -3067,7 +3063,7 @@ bool intel_can_enable_sagv(struct
> > > > > drm_atomic_state *state)
> > > > >
> > > > > latency = dev_priv->wm.skl_latency[level];
> > > > >
> > > > > - if (skl_needs_memory_bw_wa(intel_state) &&
> > > > > + if (intel_needs_memory_bw_wa(intel_state) &&
> > > > > plane->base.state->fb->modifier ==
> > > > > I915_FORMAT_MOD_X_TILED)
> > > > > latency += 15;
> > > > > @@ -3597,7 +3593,7 @@ static int skl_compute_plane_wm(const
> > > > > struct
> > > > > drm_i915_private *dev_priv,
> > > > > uint32_t y_min_scanlines;
> > > > > struct intel_atomic_state *state =
> > > > > to_intel_atomic_state(cstate->base.state);
> > > > > - bool apply_memory_bw_wa =
> > > > > skl_needs_memory_bw_wa(state);
> > > > > + enum watermark_memory_wa mem_wa;
> > > > > bool y_tiled, x_tiled;
> > > > >
> > > > > if (latency == 0 || !cstate->base.active ||
> > > > > !intel_pstate-
> > > > > >
> > > > > > base.visible) {
> > > > > @@ -3613,7 +3609,8 @@ static int skl_compute_plane_wm(const
> > > > > struct
> > > > > drm_i915_private *dev_priv,
> > > > > if (IS_KABYLAKE(dev_priv) && dev_priv-
> > > > > >ipc_enabled)
> > > > > latency += 4;
> > > > >
> > > > > - if (apply_memory_bw_wa && x_tiled)
> > > > > + mem_wa = state->wm_results.mem_wa;
> > > > > + if (mem_wa != WATERMARK_WA_NONE && x_tiled)
> > > > > latency += 15;
> > > > >
> > > > > width = drm_rect_width(&intel_pstate->base.src) >>
> > > > > 16;
> > > > > @@ -3648,7 +3645,7 @@ static int skl_compute_plane_wm(const
> > > > > struct
> > > > > drm_i915_private *dev_priv,
> > > > > y_min_scanlines = 4;
> > > > > }
> > > > >
> > > > > - if (apply_memory_bw_wa)
> > > > > + if (mem_wa == WATERMARK_WA_Y_TILED)
> > > > > y_min_scanlines *= 2;
> > > > >
> > > > > plane_bytes_per_line = width * cpp;
> > > > > @@ -4077,6 +4074,15 @@ skl_compute_ddb(struct
> > > > > drm_atomic_state
> > > > > *state)
> > > > > }
> > > > >
> > > > > /*
> > > > > + * If Watermark workaround is changed we need to
> > > > > recalculate
> > > > > + * watermark values for all active pipes
> > > > > + */
> > > > > + if (intel_state->wm_results.mem_wa != dev_priv-
> > > > > >
> > > > > > wm.skl_hw.mem_wa) {
> > > > > + realloc_pipes = ~0;
> > > > > + intel_state->wm_results.dirty_pipes = ~0;
> > > > > + }
> > > > > +
> > > > > + /*
> > > > > * We're not recomputing for the pipes not
> > > > > included in
> > > > > the
> > > > > commit, so
> > > > > * make sure we start with the current state.
> > > > > */
> > > > > @@ -4102,6 +4108,129 @@ skl_compute_ddb(struct
> > > > > drm_atomic_state
> > > > > *state)
> > > > > }
> > > > >
> > > > > static void
> > > > > +skl_compute_memory_bandwidth_wm_wa(struct drm_atomic_state
> > > > > *state)
> > > > > +{
> > > > > + struct drm_device *dev = state->dev;
> > > > > + struct drm_i915_private *dev_priv = to_i915(dev);
> > > > > + struct intel_crtc *intel_crtc;
> > > > > + struct intel_plane_state *intel_pstate;
> > > > > + struct intel_atomic_state *intel_state =
> > > > > to_intel_atomic_state(state);
> > > > > + struct memdev_info *memdev_info = &dev_priv-
> > > > > >
> > > > > > memdev_info;
> > > > > + int num_active_pipes;
> > > > > + uint32_t max_pipe_bw_kbps, total_pipe_bw_kbps;
> > > > > + int display_bw_percentage;
> > > > > + bool y_tile_enabled = false;
> > > > > +
> > > > > + if (!intel_needs_memory_bw_wa(intel_state)) {
> > > > > + intel_state->wm_results.mem_wa =
> > > > > WATERMARK_WA_NONE;
> > > > > + return;
> > > > > + }
> > > > > +
> > > > > + if (!memdev_info->valid)
> > > > > + goto exit;
> > > > > +
> > > > > + max_pipe_bw_kbps = 0;
> > > > > + num_active_pipes = 0;
> > > > > + for_each_intel_crtc(dev, intel_crtc) {
> > > > > + struct intel_crtc_state *cstate;
> > > > > + struct intel_plane *plane;
> > > > > + int num_active_planes;
> > > > > + uint32_t max_plane_bw_kbps, pipe_bw_kbps;
> > > > > +
> > > > > + /*
> > > > > + * If CRTC is part of current atomic commit,
> > > > > get
> > > > > crtc state from
> > > > > + * existing CRTC state. else take the cached
> > > > > CRTC
> > > > > state
> > > > > + */
> > > > > + cstate = NULL;
> > > > > + if (state)
> > > > > + cstate =
> > > > > intel_atomic_get_existing_crtc_state(state,
> > > > > + intel_crtc);
> > > > > + if (!cstate)
> > > > > + cstate =
> > > > > to_intel_crtc_state(intel_crtc-
> > > > > >
> > > > > > base.state);
> > > > This is really really not allowed. If you want to access
> > > > crtc->state, you need to get the state.
> > > >
> > > > Since a w/a forces a full recalculation, best you can do is put
> > > > the
> > > > per
> > > > pipe status in crtc_state->wm.skl as well. If it changes you
> > > > could
> > > > add
> > > > all other pipes.
> > > I really don't want to add all pipes in "state" until that is
> > > necessary
> > > otherwise it'll make our commit huge, that's why getting the
> > > cached
> > > state.
> > > Same goes for plane. Later if w/a changes then I'm adding all
> > > the
> > > CRTC's in relloc_pipes mask.
> > >
> > > if (intel_state->wm_results.mem_wa != dev_priv-
> > > >
> > > > wm.skl_hw.mem_wa)
> > > If I hold the crtc->mutex or plane->mutex lock, It may cause
> > > deadlock
> > > with other commits.
> > > I can keep a cached copy of plane memory bandwidth requirement in
> > > "dev_priv->wm.skl_hw", but again if there are two parallel
> > > commits
> > > it
> > > may cause race.
> > >
> > > Can you please suggest what is the correct way of getting
> > > plane/crtc
> > > state during check phase without have to actually commit them
> > > (add
> > > in
> > > global-state),
> > > If any such thing is available in atomic framework?
> > How often will the workaround status change in practice?
> In Linux use-case status changes very rarely, If we connect multiple
> high resolution display & our DRAM's bandwidth is less we may have
> to
> enable the WA.
> & it'll remain there until any display in unplugged OR any modeset
> with
> lower resolution.
> On the other hand, In OS with multi-plane enabled, WA may change if
> any
> plane is enabled/disabled (based on total bandwidth requirement for
> display)
> >
> > You could do same as active_crtcs, protect changing the workaround
> > current crtc's workaround mode in dev_priv->wm.skl.wa_state[pipe]
> > with
> > connection_mutex. If this means changing that the global workaround
> > setting is changed, then also acquire all other crtc states.
> This is not per-CRTC WA, this is complete display-system level WA. &
> depends upon total memory requirement of display.
> As you suggested I can keep the status(bandwidth requirement) for
> each
> pipe in dev_priv->wm.skl.wa_state/bandwidth[pipe], and access it
> with
> some mutex.
> Is connection mutex is right mutex to hold, what about wm_mutex?
It's nasty to do so, but it would work. connection_mutex is a ww_mutex.
But I don't think this situation will happen often, so if the w/a for
current crtc changes, won't it be better to just grab all states
anyway? I don't think the optimization is worth the complexity it
introduces you run the numbers in normal use.
~Maarten
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