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SubjectRe: [PATCH 1/2] drm/mediatek: Only block updates to CRTCs that have a pending update
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Hi, Bibby:

On Fri, 2019-08-30 at 15:38 +0800, Bibby Hsieh wrote:
> Currently we use a single mutex to allow only a single atomic
> update at a time. In truth, though, we really only want to
> ensure that only a single atomic update is allowed per CRTC.
>
> In other words, for each atomic update, we only block if there
> is a pending update for the CRTCs involved, and don't block if
> there are only pending updates for other CRTCs.

I don't know why this patch is so complicated. The original problem is
that one mutex for whole drm would block different crtc. So I think each
crtc has its own mutex would solve this problem and we need not the
event waiting. Do I miss something?

Regards,
CK

>
> Fixes: 119f5173628a ("drm/mediatek: Add DRM Driver for Mediatek SoC MT8173.")
>
> Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
> Signed-off-by: Bibby Hsieh <bibby.hsieh@mediatek.com>
> ---
> drivers/gpu/drm/mediatek/mtk_drm_crtc.c | 14 +-
> drivers/gpu/drm/mediatek/mtk_drm_drv.c | 182 +++++++++++++++++++++---
> drivers/gpu/drm/mediatek/mtk_drm_drv.h | 12 +-
> 3 files changed, 184 insertions(+), 24 deletions(-)
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> index b55970a2869d..7697b40baac0 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_crtc.c
> @@ -5,6 +5,7 @@
>
> #include <asm/barrier.h>
> #include <drm/drmP.h>
> +#include <drm/drm_atomic.h>
> #include <drm/drm_atomic_helper.h>
> #include <drm/drm_plane_helper.h>
> #include <drm/drm_probe_helper.h>
> @@ -45,6 +46,8 @@ struct mtk_drm_crtc {
> struct mtk_disp_mutex *mutex;
> unsigned int ddp_comp_nr;
> struct mtk_ddp_comp **ddp_comp;
> +
> + struct drm_crtc_state *old_crtc_state;
> };
>
> struct mtk_crtc_state {
> @@ -343,6 +346,7 @@ static void mtk_crtc_ddp_hw_fini(struct mtk_drm_crtc *mtk_crtc)
> static void mtk_crtc_ddp_config(struct drm_crtc *crtc)
> {
> struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> + struct drm_atomic_state *atomic_state = mtk_crtc->old_crtc_state->state;
> struct mtk_crtc_state *state = to_mtk_crtc_state(mtk_crtc->base.state);
> struct mtk_ddp_comp *comp = mtk_crtc->ddp_comp[0];
> unsigned int i;
> @@ -382,6 +386,7 @@ static void mtk_crtc_ddp_config(struct drm_crtc *crtc)
> }
> }
> mtk_crtc->pending_planes = false;
> + mtk_atomic_state_put_queue(atomic_state);
> }
> }
>
> @@ -451,6 +456,7 @@ static void mtk_drm_crtc_atomic_begin(struct drm_crtc *crtc,
> static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
> struct drm_crtc_state *old_crtc_state)
> {
> + struct drm_atomic_state *old_atomic_state = old_crtc_state->state;
> struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> struct mtk_drm_private *priv = crtc->dev->dev_private;
> unsigned int pending_planes = 0;
> @@ -469,8 +475,13 @@ static void mtk_drm_crtc_atomic_flush(struct drm_crtc *crtc,
> pending_planes |= BIT(i);
> }
> }
> - if (pending_planes)
> +
> + if (pending_planes) {
> mtk_crtc->pending_planes = true;
> + drm_atomic_state_get(old_atomic_state);
> + mtk_crtc->old_crtc_state = old_crtc_state;
> + }
> +
> if (crtc->state->color_mgmt_changed)
> for (i = 0; i < mtk_crtc->ddp_comp_nr; i++)
> mtk_ddp_gamma_set(mtk_crtc->ddp_comp[i], crtc->state);
> @@ -526,6 +537,7 @@ static int mtk_drm_crtc_init(struct drm_device *drm,
>
> void mtk_crtc_ddp_irq(struct drm_crtc *crtc, struct mtk_ddp_comp *comp)
> {
> +
> struct mtk_drm_crtc *mtk_crtc = to_mtk_crtc(crtc);
> struct mtk_drm_private *priv = crtc->dev->dev_private;
>
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> index c0928b69dc43..b0308a3a7483 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
> @@ -31,11 +31,120 @@
> #define DRIVER_MAJOR 1
> #define DRIVER_MINOR 0
>
> -static void mtk_atomic_schedule(struct mtk_drm_private *private,
> +struct mtk_atomic_state {
> + struct drm_atomic_state base;
> + struct list_head list;
> + struct work_struct work;
> +};
> +
> +static inline struct mtk_atomic_state *to_mtk_state(struct drm_atomic_state *s)
> +{
> + return container_of(s, struct mtk_atomic_state, base);
> +}
> +
> +void mtk_atomic_state_put_queue(struct drm_atomic_state *state)
> +{
> + struct drm_device *drm = state->dev;
> + struct mtk_drm_private *mtk_drm = drm->dev_private;
> + struct mtk_atomic_state *mtk_state = to_mtk_state(state);
> + unsigned long flags;
> +
> + spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
> + list_add_tail(&mtk_state->list, &mtk_drm->unreference.list);
> + spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
> +
> + schedule_work(&mtk_drm->unreference.work);
> +}
> +
> +static uint32_t mtk_atomic_crtc_mask(struct drm_device *drm,
> + struct drm_atomic_state *state)
> +{
> + uint32_t crtc_mask;
> + int i;
> +
> + for (i = 0, crtc_mask = 0; i < drm->mode_config.num_crtc; i++) {
> + struct drm_crtc *crtc = state->crtcs[i].ptr;
> +
> + if (crtc)
> + crtc_mask |= (1 << drm_crtc_index(crtc));
> + }
> +
> + return crtc_mask;
> +}
> +
> +/*
> + * Block until specified crtcs are no longer pending update, and atomically
> + * mark them as pending update.
> + */
> +static int mtk_atomic_get_crtcs(struct drm_device *drm,
> + struct drm_atomic_state *state)
> +{
> + struct mtk_drm_private *private = drm->dev_private;
> + uint32_t crtc_mask;
> + int ret;
> +
> + crtc_mask = mtk_atomic_crtc_mask(drm, state);
> +
> + /*
> + * Wait for all pending updates to complete for the set of crtcs being
> + * changed in this atomic commit
> + */
> + spin_lock(&private->commit.crtcs_event.lock);
> + ret = wait_event_interruptible_locked(private->commit.crtcs_event,
> + !(private->commit.crtcs & crtc_mask));
> + if (ret == 0)
> + private->commit.crtcs |= crtc_mask;
> + spin_unlock(&private->commit.crtcs_event.lock);
> +
> + return ret;
> +}
> +
> +/*
> + * Mark specified crtcs as no longer pending update.
> + */
> +static void mtk_atomic_put_crtcs(struct drm_device *drm,
> + struct drm_atomic_state *state)
> +{
> + struct mtk_drm_private *private = drm->dev_private;
> + uint32_t crtc_mask;
> +
> + crtc_mask = mtk_atomic_crtc_mask(drm, state);
> +
> + spin_lock(&private->commit.crtcs_event.lock);
> + private->commit.crtcs &= ~crtc_mask;
> + wake_up_all_locked(&private->commit.crtcs_event);
> + spin_unlock(&private->commit.crtcs_event.lock);
> +}
> +
> +static void mtk_unreference_work(struct work_struct *work)
> +{
> + struct mtk_drm_private *mtk_drm = container_of(work,
> + struct mtk_drm_private, unreference.work);
> + unsigned long flags;
> + struct mtk_atomic_state *state, *tmp;
> +
> + /*
> + * framebuffers cannot be unreferenced in atomic context.
> + * Therefore, only hold the spinlock when iterating unreference_list,
> + * and drop it when doing the unreference.
> + */
> + spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
> + list_for_each_entry_safe(state, tmp, &mtk_drm->unreference.list, list) {
> + list_del(&state->list);
> + spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
> + drm_atomic_state_put(&state->base);
> + spin_lock_irqsave(&mtk_drm->unreference.lock, flags);
> + }
> + spin_unlock_irqrestore(&mtk_drm->unreference.lock, flags);
> +}
> +
> +
> +static void mtk_atomic_schedule(struct drm_device *drm,
> struct drm_atomic_state *state)
> {
> - private->commit.state = state;
> - schedule_work(&private->commit.work);
> + struct mtk_atomic_state *mtk_state = to_mtk_state(state);
> +
> + schedule_work(&mtk_state->work);
> }
>
> static void mtk_atomic_wait_for_fences(struct drm_atomic_state *state)
> @@ -48,13 +157,10 @@ static void mtk_atomic_wait_for_fences(struct drm_atomic_state *state)
> mtk_fb_wait(new_plane_state->fb);
> }
>
> -static void mtk_atomic_complete(struct mtk_drm_private *private,
> +static void mtk_atomic_complete(struct drm_device *drm,
> struct drm_atomic_state *state)
> {
> - struct drm_device *drm = private->drm;
> -
> mtk_atomic_wait_for_fences(state);
> -
> /*
> * Mediatek drm supports runtime PM, so plane registers cannot be
> * written when their crtc is disabled.
> @@ -77,53 +183,86 @@ static void mtk_atomic_complete(struct mtk_drm_private *private,
> drm_atomic_helper_wait_for_vblanks(drm, state);
>
> drm_atomic_helper_cleanup_planes(drm, state);
> + mtk_atomic_put_crtcs(drm, state);
> +
> drm_atomic_state_put(state);
> }
>
> static void mtk_atomic_work(struct work_struct *work)
> {
> - struct mtk_drm_private *private = container_of(work,
> - struct mtk_drm_private, commit.work);
> + struct mtk_atomic_state *mtk_state = container_of(work,
> + struct mtk_atomic_state, work);
> + struct drm_atomic_state *state = &mtk_state->base;
> + struct drm_device *drm = state->dev;
>
> - mtk_atomic_complete(private, private->commit.state);
> + mtk_atomic_complete(drm, state);
> }
>
> static int mtk_atomic_commit(struct drm_device *drm,
> struct drm_atomic_state *state,
> bool async)
> {
> - struct mtk_drm_private *private = drm->dev_private;
> int ret;
>
> ret = drm_atomic_helper_prepare_planes(drm, state);
> if (ret)
> return ret;
>
> - mutex_lock(&private->commit.lock);
> - flush_work(&private->commit.work);
> + ret = mtk_atomic_get_crtcs(drm, state);
> + if (ret) {
> + drm_atomic_helper_cleanup_planes(drm, state);
> + return ret;
> + }
>
> ret = drm_atomic_helper_swap_state(state, true);
> if (ret) {
> - mutex_unlock(&private->commit.lock);
> drm_atomic_helper_cleanup_planes(drm, state);
> return ret;
> }
>
> drm_atomic_state_get(state);
> if (async)
> - mtk_atomic_schedule(private, state);
> + mtk_atomic_schedule(drm, state);
> else
> - mtk_atomic_complete(private, state);
> -
> - mutex_unlock(&private->commit.lock);
> + mtk_atomic_complete(drm, state);
>
> return 0;
> }
>
> +static struct drm_atomic_state *mtk_drm_atomic_state_alloc(
> + struct drm_device *dev)
> +{
> + struct mtk_atomic_state *mtk_state;
> +
> + mtk_state = kzalloc(sizeof(*mtk_state), GFP_KERNEL);
> + if (!mtk_state)
> + return NULL;
> +
> + if (drm_atomic_state_init(dev, &mtk_state->base) < 0) {
> + kfree(mtk_state);
> + return NULL;
> + }
> +
> + INIT_LIST_HEAD(&mtk_state->list);
> + INIT_WORK(&mtk_state->work, mtk_atomic_work);
> +
> + return &mtk_state->base;
> +}
> +
> +static void mtk_drm_atomic_state_free(struct drm_atomic_state *state)
> +{
> + struct mtk_atomic_state *mtk_state = to_mtk_state(state);
> +
> + drm_atomic_state_default_release(state);
> + kfree(mtk_state);
> +}
> +
> static const struct drm_mode_config_funcs mtk_drm_mode_config_funcs = {
> .fb_create = mtk_drm_mode_fb_create,
> .atomic_check = drm_atomic_helper_check,
> .atomic_commit = mtk_atomic_commit,
> + .atomic_state_alloc = mtk_drm_atomic_state_alloc,
> + .atomic_state_free = mtk_drm_atomic_state_free
> };
>
> static const enum mtk_ddp_comp_id mt2701_mtk_ddp_main[] = {
> @@ -319,6 +458,11 @@ static int mtk_drm_kms_init(struct drm_device *drm)
> drm_kms_helper_poll_init(drm);
> drm_mode_config_reset(drm);
>
> + INIT_WORK(&private->unreference.work, mtk_unreference_work);
> + INIT_LIST_HEAD(&private->unreference.list);
> + spin_lock_init(&private->unreference.lock);
> + init_waitqueue_head(&private->commit.crtcs_event);
> +
> return 0;
>
> err_component_unbind:
> @@ -504,8 +648,6 @@ static int mtk_drm_probe(struct platform_device *pdev)
> if (!private)
> return -ENOMEM;
>
> - mutex_init(&private->commit.lock);
> - INIT_WORK(&private->commit.work, mtk_atomic_work);
> private->data = of_device_get_match_data(dev);
>
> mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> index 823ba4081c18..0934f83b860d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
> @@ -48,12 +48,16 @@ struct mtk_drm_private {
> const struct mtk_mmsys_driver_data *data;
>
> struct {
> - struct drm_atomic_state *state;
> - struct work_struct work;
> - struct mutex lock;
> + uint32_t crtcs;
> + wait_queue_head_t crtcs_event;
> } commit;
>
> struct drm_atomic_state *suspend_state;
> + struct {
> + struct work_struct work;
> + struct list_head list;
> + spinlock_t lock;
> + } unreference;
> };
>
> extern struct platform_driver mtk_ddp_driver;
> @@ -64,4 +68,6 @@ extern struct platform_driver mtk_dpi_driver;
> extern struct platform_driver mtk_dsi_driver;
> extern struct platform_driver mtk_mipi_tx_driver;
>
> +void mtk_atomic_state_put_queue(struct drm_atomic_state *state);
> +
> #endif /* MTK_DRM_DRV_H */


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