--- /dev/null
+From 9d0e3cac3517942a6e00eeecfe583a98715edb16 Mon Sep 17 00:00:00 2001
+From: Brian Norris <briannorris@chromium.org>
+Date: Mon, 9 Jan 2023 17:18:16 -0800
+Subject: drm/atomic: Allow vblank-enabled + self-refresh "disable"
+
+From: Brian Norris <briannorris@chromium.org>
+
+commit 9d0e3cac3517942a6e00eeecfe583a98715edb16 upstream.
+
+The self-refresh helper framework overloads "disable" to sometimes mean
+"go into self-refresh mode," and this mode activates automatically
+(e.g., after some period of unchanging display output). In such cases,
+the display pipe is still considered "on", and user-space is not aware
+that we went into self-refresh mode. Thus, users may expect that
+vblank-related features (such as DRM_IOCTL_WAIT_VBLANK) still work
+properly.
+
+However, we trigger the WARN_ONCE() here if a CRTC driver tries to leave
+vblank enabled.
+
+Add a different expectation: that CRTCs *should* leave vblank enabled
+when going into self-refresh.
+
+This patch is preparation for another patch -- "drm/rockchip: vop: Leave
+vblank enabled in self-refresh" -- which resolves conflicts between the
+above self-refresh behavior and the API tests in IGT's kms_vblank test
+module.
+
+== Some alternatives discussed: ==
+
+It's likely that on many display controllers, vblank interrupts will
+turn off when the CRTC is disabled, and so in some cases, self-refresh
+may not support vblank. To support such cases, we might consider
+additions to the generic helpers such that we fire vblank events based
+on a timer.
+
+However, there is currently only one driver using the common
+self-refresh helpers (i.e., rockchip), and at least as of commit
+bed030a49f3e ("drm/rockchip: Don't fully disable vop on self refresh"),
+the CRTC hardware is powered enough to continue to generate vblank
+interrupts.
+
+So we chose the simpler option of leaving vblank interrupts enabled. We
+can reevaluate this decision and perhaps augment the helpers if/when we
+gain a second driver that has different requirements.
+
+v3:
+ * include discussion summary
+
+v2:
+ * add 'ret != 0' warning case for self-refresh
+ * describe failing test case and relation to drm/rockchip patch better
+
+Cc: <stable@vger.kernel.org> # dependency for "drm/rockchip: vop: Leave
+ # vblank enabled in self-refresh"
+Signed-off-by: Brian Norris <briannorris@chromium.org>
+Signed-off-by: Sean Paul <seanpaul@chromium.org>
+Link: https://patchwork.freedesktop.org/patch/msgid/20230109171809.v3.1.I3904f697863649eb1be540ecca147a66e42bfad7@changeid
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/gpu/drm/drm_atomic_helper.c | 11 ++++++++++-
+ 1 file changed, 10 insertions(+), 1 deletion(-)
+
+--- a/drivers/gpu/drm/drm_atomic_helper.c
++++ b/drivers/gpu/drm/drm_atomic_helper.c
+@@ -1086,7 +1086,16 @@ disable_outputs(struct drm_device *dev,
+ continue;
+
+ ret = drm_crtc_vblank_get(crtc);
+- WARN_ONCE(ret != -EINVAL, "driver forgot to call drm_crtc_vblank_off()\n");
++ /*
++ * Self-refresh is not a true "disable"; ensure vblank remains
++ * enabled.
++ */
++ if (new_crtc_state->self_refresh_active)
++ WARN_ONCE(ret != 0,
++ "driver disabled vblank in self-refresh\n");
++ else
++ WARN_ONCE(ret != -EINVAL,
++ "driver forgot to call drm_crtc_vblank_off()\n");
+ if (ret == 0)
+ drm_crtc_vblank_put(crtc);
+ }
--- /dev/null
+From 2bdba9d4a3baa758c2ca7f5b37b35c7b3391dc42 Mon Sep 17 00:00:00 2001
+From: Brian Norris <briannorris@chromium.org>
+Date: Mon, 9 Jan 2023 17:18:17 -0800
+Subject: drm/rockchip: vop: Leave vblank enabled in self-refresh
+
+From: Brian Norris <briannorris@chromium.org>
+
+commit 2bdba9d4a3baa758c2ca7f5b37b35c7b3391dc42 upstream.
+
+If we disable vblank when entering self-refresh, vblank APIs (like
+DRM_IOCTL_WAIT_VBLANK) no longer work. But user space is not aware when
+we enter self-refresh, so this appears to be an API violation -- that
+DRM_IOCTL_WAIT_VBLANK fails with EINVAL whenever the display is idle and
+enters self-refresh.
+
+The downstream driver used by many of these systems never used to
+disable vblank for PSR, and in fact, even upstream, we didn't do that
+until radically redesigning the state machine in commit 6c836d965bad
+("drm/rockchip: Use the helpers for PSR").
+
+Thus, it seems like a reasonable API fix to simply restore that
+behavior, and leave vblank enabled.
+
+Note that this appears to potentially unbalance the
+drm_crtc_vblank_{off,on}() calls in some cases, but:
+(a) drm_crtc_vblank_on() documents this as OK and
+(b) if I do the naive balancing, I find state machine issues such that
+ we're not in sync properly; so it's easier to take advantage of (a).
+
+This issue was exposed by IGT's kms_vblank tests, and reported by
+KernelCI. The bug has been around a while (longer than KernelCI
+noticed), but was only exposed once self-refresh was bugfixed more
+recently, and so KernelCI could properly test it. Some other notes in:
+
+ https://lore.kernel.org/dri-devel/Y6OCg9BPnJvimQLT@google.com/
+ Re: renesas/master bisection: igt-kms-rockchip.kms_vblank.pipe-A-wait-forked on rk3399-gru-kevin
+
+== Backporting notes: ==
+
+Marking as 'Fixes' commit 6c836d965bad ("drm/rockchip: Use the helpers
+for PSR"), but it probably depends on commit bed030a49f3e
+("drm/rockchip: Don't fully disable vop on self refresh") as well.
+
+We also need the previous patch ("drm/atomic: Allow vblank-enabled +
+self-refresh "disable""), of course.
+
+v3:
+ * no update
+
+v2:
+ * skip unnecessary lock/unlock
+
+Fixes: 6c836d965bad ("drm/rockchip: Use the helpers for PSR")
+Cc: <stable@vger.kernel.org>
+Reported-by: "kernelci.org bot" <bot@kernelci.org>
+Link: https://lore.kernel.org/dri-devel/Y5itf0+yNIQa6fU4@sirena.org.uk/
+Signed-off-by: Brian Norris <briannorris@chromium.org>
+Signed-off-by: Sean Paul <seanpaul@chromium.org>
+Link: https://patchwork.freedesktop.org/patch/msgid/20230109171809.v3.2.Ic07cba4ab9a7bd3618a9e4258b8f92ea7d10ae5a@changeid
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/gpu/drm/rockchip/rockchip_drm_vop.c | 8 ++++----
+ 1 file changed, 4 insertions(+), 4 deletions(-)
+
+--- a/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
++++ b/drivers/gpu/drm/rockchip/rockchip_drm_vop.c
+@@ -654,13 +654,13 @@ static void vop_crtc_atomic_disable(stru
+ if (crtc->state->self_refresh_active)
+ rockchip_drm_set_win_enabled(crtc, false);
+
++ if (crtc->state->self_refresh_active)
++ goto out;
++
+ mutex_lock(&vop->vop_lock);
+
+ drm_crtc_vblank_off(crtc);
+
+- if (crtc->state->self_refresh_active)
+- goto out;
+-
+ /*
+ * Vop standby will take effect at end of current frame,
+ * if dsp hold valid irq happen, it means standby complete.
+@@ -692,9 +692,9 @@ static void vop_crtc_atomic_disable(stru
+ vop_core_clks_disable(vop);
+ pm_runtime_put(vop->dev);
+
+-out:
+ mutex_unlock(&vop->vop_lock);
+
++out:
+ if (crtc->state->event && !crtc->state->active) {
+ spin_lock_irq(&crtc->dev->event_lock);
+ drm_crtc_send_vblank_event(crtc, crtc->state->event);
projects / thirdparty / kernel / stable-queue.git / commitdiff
