From: thongsyho thong.ho.px@rvc.renesas.com

commit 641307df71fe77d7b38a477067495ede05d47295 upstream.

When stopping the CRTC the driver must disable all planes and wait for the change to take effect at the next vblank. Merely calling drm_crtc_wait_one_vblank() is not enough, as the function doesn't include any mechanism to handle the race with vblank interrupts.

Replace the drm_crtc_wait_one_vblank() call with a manual mechanism that handles the vblank interrupt race.

Cc: stable@vger.kernel.org Signed-off-by: Laurent Pinchart laurent.pinchart+renesas@ideasonboard.com Reviewed-by: Kieran Bingham kieran.bingham+renesas@ideasonboard.com Signed-off-by: thongsyho thong.ho.px@rvc.renesas.com --- drivers/gpu/drm/rcar-du/rcar_du_crtc.c | 53 ++++++++++++++++++++++++++++++---- drivers/gpu/drm/rcar-du/rcar_du_crtc.h | 8 +++++ 2 files changed, 55 insertions(+), 6 deletions(-)

diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c index 848f7f2..3322b15 100644 --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.c +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.c @@ -392,6 +392,31 @@ static void rcar_du_crtc_start(struct rcar_du_crtc *rcrtc) rcrtc->started = true; }

+static void rcar_du_crtc_disable_planes(struct rcar_du_crtc *rcrtc) +{ + struct rcar_du_device *rcdu = rcrtc->group->dev; + struct drm_crtc *crtc = &rcrtc->crtc; + u32 status; + /* Make sure vblank interrupts are enabled. */ + drm_crtc_vblank_get(crtc); + /* + * Disable planes and calculate how many vertical blanking interrupts we + * have to wait for. If a vertical blanking interrupt has been triggered + * but not processed yet, we don't know whether it occurred before or + * after the planes got disabled. We thus have to wait for two vblank + * interrupts in that case. + */ + spin_lock_irq(&rcrtc->vblank_lock); + rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR, 0); + status = rcar_du_crtc_read(rcrtc, DSSR); + rcrtc->vblank_count = status & DSSR_VBK ? 2 : 1; + spin_unlock_irq(&rcrtc->vblank_lock); + if (!wait_event_timeout(rcrtc->vblank_wait, rcrtc->vblank_count == 0, + msecs_to_jiffies(100))) + dev_warn(rcdu->dev, "vertical blanking timeout\n"); + drm_crtc_vblank_put(crtc); +} + static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc) { struct drm_crtc *crtc = &rcrtc->crtc; @@ -400,17 +425,16 @@ static void rcar_du_crtc_stop(struct rcar_du_crtc *rcrtc) return;

/* Disable all planes and wait for the change to take effect. This is - * required as the DSnPR registers are updated on vblank, and no vblank - * will occur once the CRTC is stopped. Disabling planes when starting - * the CRTC thus wouldn't be enough as it would start scanning out - * immediately from old frame buffers until the next vblank. + * required as the plane enable registers are updated on vblank, and no + * vblank will occur once the CRTC is stopped. Disabling planes when + * starting the CRTC thus wouldn't be enough as it would start scanning + * out immediately from old frame buffers until the next vblank. * * This increases the CRTC stop delay, especially when multiple CRTCs * are stopped in one operation as we now wait for one vblank per CRTC. * Whether this can be improved needs to be researched. */ - rcar_du_group_write(rcrtc->group, rcrtc->index % 2 ? DS2PR : DS1PR, 0); - drm_crtc_wait_one_vblank(crtc); + rcar_du_crtc_disable_planes(rcrtc);

/* Disable vertical blanking interrupt reporting. We first need to wait * for page flip completion before stopping the CRTC as userspace @@ -548,10 +572,25 @@ static irqreturn_t rcar_du_crtc_irq(int irq, void *arg) irqreturn_t ret = IRQ_NONE; u32 status;

+ spin_lock(&rcrtc->vblank_lock); + status = rcar_du_crtc_read(rcrtc, DSSR); rcar_du_crtc_write(rcrtc, DSRCR, status & DSRCR_MASK);

if (status & DSSR_VBK) { + /* + * Wake up the vblank wait if the counter reaches 0. This must + * be protected by the vblank_lock to avoid races in + * rcar_du_crtc_disable_planes(). + */ + if (rcrtc->vblank_count) { + if (--rcrtc->vblank_count == 0) + wake_up(&rcrtc->vblank_wait); + } + } + spin_unlock(&rcrtc->vblank_lock); + + if (status & DSSR_VBK) { drm_crtc_handle_vblank(&rcrtc->crtc); rcar_du_crtc_finish_page_flip(rcrtc); ret = IRQ_HANDLED; @@ -606,6 +645,8 @@ int rcar_du_crtc_create(struct rcar_du_group *rgrp, unsigned int index) }

init_waitqueue_head(&rcrtc->flip_wait); + init_waitqueue_head(&rcrtc->vblank_wait); + spin_lock_init(&rcrtc->vblank_lock);

rcrtc->group = rgrp; rcrtc->mmio_offset = mmio_offsets[index]; diff --git a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h index 6f08b7e..48bef05 100644 --- a/drivers/gpu/drm/rcar-du/rcar_du_crtc.h +++ b/drivers/gpu/drm/rcar-du/rcar_du_crtc.h @@ -15,6 +15,7 @@ #define __RCAR_DU_CRTC_H__

#include <linux/mutex.h> +#include <linux/spinlock.h> #include <linux/wait.h>

#include <drm/drmP.h> @@ -33,6 +34,9 @@ * @started: whether the CRTC has been started and is running * @event: event to post when the pending page flip completes * @flip_wait: wait queue used to signal page flip completion + * @vblank_lock: protects vblank_wait and vblank_count + * @vblank_wait: wait queue used to signal vertical blanking + * @vblank_count: number of vertical blanking interrupts to wait for * @outputs: bitmask of the outputs (enum rcar_du_output) driven by this CRTC * @group: CRTC group this CRTC belongs to */ @@ -48,6 +52,10 @@ struct rcar_du_crtc { struct drm_pending_vblank_event *event; wait_queue_head_t flip_wait;

+ spinlock_t vblank_lock; + wait_queue_head_t vblank_wait; + unsigned int vblank_count; + unsigned int outputs;

struct rcar_du_group *group;