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Subject[PATCH REBASED v10 3/6] drm/i915/skl: Update plane watermarks atomically during plane updates
Date
Thanks to Ville for suggesting this as a potential solution to pipe
underruns on Skylake.

On Skylake all of the registers for configuring planes, including the
registers for configuring their watermarks, are double buffered. New
values written to them won't take effect until said registers are
"armed", which is done by writing to the PLANE_SURF (or in the case of
cursor planes, the CURBASE register) register.

With this in mind, up until now we've been updating watermarks on skl
like this:

non-modeset {
- calculate (during atomic check phase)
- finish_atomic_commit:
- intel_pre_plane_update:
- intel_update_watermarks()
- {vblank happens; new watermarks + old plane values => underrun }
- drm_atomic_helper_commit_planes_on_crtc:
- start vblank evasion
- write new plane registers
- end vblank evasion
}

or

modeset {
- calculate (during atomic check phase)
- finish_atomic_commit:
- crtc_enable:
- intel_update_watermarks()
- {vblank happens; new watermarks + old plane values => underrun }
- drm_atomic_helper_commit_planes_on_crtc:
- start vblank evasion
- write new plane registers
- end vblank evasion
}

Now we update watermarks atomically like this:

non-modeset {
- calculate (during atomic check phase)
- finish_atomic_commit:
- intel_pre_plane_update:
- intel_update_watermarks() (wm values aren't written yet)
- drm_atomic_helper_commit_planes_on_crtc:
- start vblank evasion
- write new plane registers
- write new wm values
- end vblank evasion
}

modeset {
- calculate (during atomic check phase)
- finish_atomic_commit:
- crtc_enable:
- intel_update_watermarks() (actual wm values aren't written
yet)
- drm_atomic_helper_commit_planes_on_crtc:
- start vblank evasion
- write new plane registers
- write new wm values
- end vblank evasion
}

So this patch moves all of the watermark writes into the right place;
inside of the vblank evasion where we update all of the registers for
each plane. While this patch doesn't fix everything, it does allow us to
update the watermark values in the way the hardware expects us to.

Changes since original patch series:
- Remove mutex_lock/mutex_unlock since they don't do anything and we're
not touching global state
- Move skl_write_cursor_wm/skl_write_plane_wm functions into
intel_pm.c, make externally visible
- Add skl_write_plane_wm calls to skl_update_plane
- Fix conditional for for loop in skl_write_plane_wm (level < max_level
should be level <= max_level)
- Make diagram in commit more accurate to what's actually happening
- Add Fixes:

Changes since v1:
- Use IS_GEN9() instead of IS_SKYLAKE() since these fixes apply to more
then just Skylake
- Update description to make it clear this patch doesn't fix everything
- Check if pipes were actually changed before writing watermarks

Changes since v2:
- Write PIPE_WM_LINETIME during vblank evasion

Changes since v3:
- Rebase against new SAGV patch changes

Changes since v4:
- Add a parameter to choose what skl_wm_values struct to use when
writing new plane watermarks

Changes since v5:
- Remove cursor ddb entry write in skl_write_cursor_wm(), defer until
patch 6
- Write WM_LINETIME in intel_begin_crtc_commit()

Changes since v6:
- Remove redundant dirty_pipes check in skl_write_plane_wm (we check
this in all places where we call this function, and it was supposed
to have been removed earlier anyway)
- In i9xx_update_cursor(), use dev_priv->info.gen >= 9 instead of
IS_GEN9(dev_priv). We do this everywhere else and I'd imagine this
needs to be done for gen10 as well

Fixes: 2d41c0b59afc ("drm/i915/skl: SKL Watermark Computation")
Signed-off-by: Lyude <cpaul@redhat.com>
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Cc: stable@vger.kernel.org
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Daniel Vetter <daniel.vetter@intel.com>
Cc: Radhakrishna Sripada <radhakrishna.sripada@intel.com>
Cc: Hans de Goede <hdegoede@redhat.com>
---
drivers/gpu/drm/i915/intel_display.c | 16 +++++++++++-
drivers/gpu/drm/i915/intel_drv.h | 5 ++++
drivers/gpu/drm/i915/intel_pm.c | 50 ++++++++++++++++++++++++------------
drivers/gpu/drm/i915/intel_sprite.c | 6 +++++
4 files changed, 60 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 302cb1f..429810b 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -2980,6 +2980,7 @@ static void skylake_update_primary_plane(struct drm_plane *plane,
struct intel_crtc *intel_crtc = to_intel_crtc(crtc_state->base.crtc);
struct drm_framebuffer *fb = plane_state->base.fb;
struct drm_i915_gem_object *obj = intel_fb_obj(fb);
+ struct skl_wm_values *wm = &dev_priv->wm.skl_results;
int pipe = intel_crtc->pipe;
u32 plane_ctl, stride_div, stride;
u32 tile_height, plane_offset, plane_size;
@@ -3031,6 +3032,9 @@ static void skylake_update_primary_plane(struct drm_plane *plane,
intel_crtc->adjusted_x = x_offset;
intel_crtc->adjusted_y = y_offset;

+ if (wm->dirty_pipes & drm_crtc_mask(&intel_crtc->base))
+ skl_write_plane_wm(intel_crtc, wm, 0);
+
I915_WRITE(PLANE_CTL(pipe, 0), plane_ctl);
I915_WRITE(PLANE_OFFSET(pipe, 0), plane_offset);
I915_WRITE(PLANE_SIZE(pipe, 0), plane_size);
@@ -10310,9 +10314,13 @@ static void i9xx_update_cursor(struct drm_crtc *crtc, u32 base,
struct drm_device *dev = crtc->dev;
struct drm_i915_private *dev_priv = to_i915(dev);
struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
+ struct skl_wm_values *wm = &dev_priv->wm.skl_results;
int pipe = intel_crtc->pipe;
uint32_t cntl = 0;

+ if (dev_priv->info.gen >= 9 && wm->dirty_pipes & drm_crtc_mask(crtc))
+ skl_write_cursor_wm(intel_crtc, wm);
+
if (plane_state && plane_state->base.visible) {
cntl = MCURSOR_GAMMA_ENABLE;
switch (plane_state->base.crtc_w) {
@@ -14222,10 +14230,12 @@ static void intel_begin_crtc_commit(struct drm_crtc *crtc,
struct drm_crtc_state *old_crtc_state)
{
struct drm_device *dev = crtc->dev;
+ struct drm_i915_private *dev_priv = to_i915(dev);
struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
struct intel_crtc_state *old_intel_state =
to_intel_crtc_state(old_crtc_state);
bool modeset = needs_modeset(crtc->state);
+ enum pipe pipe = intel_crtc->pipe;

/* Perform vblank evasion around commit operation */
intel_pipe_update_start(intel_crtc);
@@ -14240,8 +14250,12 @@ static void intel_begin_crtc_commit(struct drm_crtc *crtc,

if (to_intel_crtc_state(crtc->state)->update_pipe)
intel_update_pipe_config(intel_crtc, old_intel_state);
- else if (INTEL_INFO(dev)->gen >= 9)
+ else if (INTEL_INFO(dev)->gen >= 9) {
skl_detach_scalers(intel_crtc);
+
+ I915_WRITE(PIPE_WM_LINETIME(pipe),
+ dev_priv->wm.skl_hw.wm_linetime[pipe]);
+ }
}

static void intel_finish_crtc_commit(struct drm_crtc *crtc,
diff --git a/drivers/gpu/drm/i915/intel_drv.h b/drivers/gpu/drm/i915/intel_drv.h
index e35799d..38d58a1 100644
--- a/drivers/gpu/drm/i915/intel_drv.h
+++ b/drivers/gpu/drm/i915/intel_drv.h
@@ -1700,6 +1700,11 @@ void skl_ddb_get_hw_state(struct drm_i915_private *dev_priv,
struct skl_ddb_allocation *ddb /* out */);
int skl_enable_sagv(struct drm_i915_private *dev_priv);
int skl_disable_sagv(struct drm_i915_private *dev_priv);
+void skl_write_cursor_wm(struct intel_crtc *intel_crtc,
+ const struct skl_wm_values *wm);
+void skl_write_plane_wm(struct intel_crtc *intel_crtc,
+ const struct skl_wm_values *wm,
+ int plane);
uint32_t ilk_pipe_pixel_rate(const struct intel_crtc_state *pipe_config);
bool ilk_disable_lp_wm(struct drm_device *dev);
int sanitize_rc6_option(struct drm_i915_private *dev_priv, int enable_rc6);
diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
index ee6590d..df0fab6 100644
--- a/drivers/gpu/drm/i915/intel_pm.c
+++ b/drivers/gpu/drm/i915/intel_pm.c
@@ -3800,6 +3800,39 @@ static void skl_ddb_entry_write(struct drm_i915_private *dev_priv,
I915_WRITE(reg, 0);
}

+void skl_write_plane_wm(struct intel_crtc *intel_crtc,
+ const struct skl_wm_values *wm,
+ int plane)
+{
+ struct drm_crtc *crtc = &intel_crtc->base;
+ struct drm_device *dev = crtc->dev;
+ struct drm_i915_private *dev_priv = to_i915(dev);
+ int level, max_level = ilk_wm_max_level(dev);
+ enum pipe pipe = intel_crtc->pipe;
+
+ for (level = 0; level <= max_level; level++) {
+ I915_WRITE(PLANE_WM(pipe, plane, level),
+ wm->plane[pipe][plane][level]);
+ }
+ I915_WRITE(PLANE_WM_TRANS(pipe, plane), wm->plane_trans[pipe][plane]);
+}
+
+void skl_write_cursor_wm(struct intel_crtc *intel_crtc,
+ const struct skl_wm_values *wm)
+{
+ struct drm_crtc *crtc = &intel_crtc->base;
+ struct drm_device *dev = crtc->dev;
+ struct drm_i915_private *dev_priv = to_i915(dev);
+ int level, max_level = ilk_wm_max_level(dev);
+ enum pipe pipe = intel_crtc->pipe;
+
+ for (level = 0; level <= max_level; level++) {
+ I915_WRITE(CUR_WM(pipe, level),
+ wm->plane[pipe][PLANE_CURSOR][level]);
+ }
+ I915_WRITE(CUR_WM_TRANS(pipe), wm->plane_trans[pipe][PLANE_CURSOR]);
+}
+
static void skl_write_wm_values(struct drm_i915_private *dev_priv,
const struct skl_wm_values *new)
{
@@ -3807,7 +3840,7 @@ static void skl_write_wm_values(struct drm_i915_private *dev_priv,
struct intel_crtc *crtc;

for_each_intel_crtc(dev, crtc) {
- int i, level, max_level = ilk_wm_max_level(dev);
+ int i;
enum pipe pipe = crtc->pipe;

if ((new->dirty_pipes & drm_crtc_mask(&crtc->base)) == 0)
@@ -3815,21 +3848,6 @@ static void skl_write_wm_values(struct drm_i915_private *dev_priv,
if (!crtc->active)
continue;

- I915_WRITE(PIPE_WM_LINETIME(pipe), new->wm_linetime[pipe]);
-
- for (level = 0; level <= max_level; level++) {
- for (i = 0; i < intel_num_planes(crtc); i++)
- I915_WRITE(PLANE_WM(pipe, i, level),
- new->plane[pipe][i][level]);
- I915_WRITE(CUR_WM(pipe, level),
- new->plane[pipe][PLANE_CURSOR][level]);
- }
- for (i = 0; i < intel_num_planes(crtc); i++)
- I915_WRITE(PLANE_WM_TRANS(pipe, i),
- new->plane_trans[pipe][i]);
- I915_WRITE(CUR_WM_TRANS(pipe),
- new->plane_trans[pipe][PLANE_CURSOR]);
-
for (i = 0; i < intel_num_planes(crtc); i++) {
skl_ddb_entry_write(dev_priv,
PLANE_BUF_CFG(pipe, i),
diff --git a/drivers/gpu/drm/i915/intel_sprite.c b/drivers/gpu/drm/i915/intel_sprite.c
index cbdca7e4..1c7e705 100644
--- a/drivers/gpu/drm/i915/intel_sprite.c
+++ b/drivers/gpu/drm/i915/intel_sprite.c
@@ -204,6 +204,9 @@ skl_update_plane(struct drm_plane *drm_plane,
struct intel_plane *intel_plane = to_intel_plane(drm_plane);
struct drm_framebuffer *fb = plane_state->base.fb;
struct drm_i915_gem_object *obj = intel_fb_obj(fb);
+ struct skl_wm_values *wm = &dev_priv->wm.skl_results;
+ struct drm_crtc *crtc = crtc_state->base.crtc;
+ struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
const int pipe = intel_plane->pipe;
const int plane = intel_plane->plane + 1;
u32 plane_ctl, stride_div, stride;
@@ -239,6 +242,9 @@ skl_update_plane(struct drm_plane *drm_plane,
crtc_w--;
crtc_h--;

+ if (wm->dirty_pipes & drm_crtc_mask(crtc))
+ skl_write_plane_wm(intel_crtc, wm, plane);
+
if (key->flags) {
I915_WRITE(PLANE_KEYVAL(pipe, plane), key->min_value);
I915_WRITE(PLANE_KEYMAX(pipe, plane), key->max_value);
--
2.7.4
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