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    Subject[PATCH v5 32/36] drm/rockchip: psr: Avoid redundant calls to .set() callback
    Date
    From: Tomasz Figa <tfiga@chromium.org>

    The first time after we call rockchip_drm_do_flush() after
    rockchip_drm_psr_register(), we go from PSR_DISABLE to PSR_FLUSH. The
    difference between PSR_DISABLE and PSR_FLUSH is whether or not we have a
    delayed work pending - PSR is off in either state. However
    psr_set_state() only catches the transition from PSR_FLUSH to
    PSR_DISABLE (which never happens), while going from PSR_DISABLE to
    PSR_FLUSH triggers a call to psr->set() to disable PSR while it's
    already disabled. This triggers the eDP PHY power-on sequence without
    being shut down first and this seems to occasionally leave the encoder
    unable to later enable PSR. Let's just simplify the state machine and
    simply consider PSR_DISABLE and PSR_FLUSH the same state. This lets us
    represent the hardware state by a simple boolean called "enabled" and,
    while at it, rename the misleading "active" boolean to "inhibit", which
    represents the purpose much better.

    Also, userspace can (and does) trigger the rockchip_drm_do_flush() path
    from drmModeDirtyFB() at any time, whether or the encoder is active. If
    no mode is set, we call into analogix_dp_psr_set() which returns -EINVAL
    because encoder->crtc is NULL. Avoid this by starting out with
    psr->allowed set to false.

    Signed-off-by: Kristian H. Kristensen <hoegsberg@chromium.org>
    Signed-off-by: Tomasz Figa <tfiga@chromium.org>
    Signed-off-by: Thierry Escande <thierry.escande@collabora.com>
    Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
    Tested-by: Marek Szyprowski <m.szyprowski@samsung.com>
    ---

    drivers/gpu/drm/rockchip/rockchip_drm_psr.c | 79 +++++++++--------------------
    1 file changed, 23 insertions(+), 56 deletions(-)

    diff --git a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
    index c8655e625ba2..448c5fde241c 100644
    --- a/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
    +++ b/drivers/gpu/drm/rockchip/rockchip_drm_psr.c
    @@ -22,19 +22,13 @@

    #define PSR_FLUSH_TIMEOUT_MS 100

    -enum psr_state {
    - PSR_FLUSH,
    - PSR_ENABLE,
    - PSR_DISABLE,
    -};
    -
    struct psr_drv {
    struct list_head list;
    struct drm_encoder *encoder;

    struct mutex lock;
    bool active;
    - enum psr_state state;
    + bool enabled;

    struct delayed_work flush_work;
    struct work_struct disable_work;
    @@ -78,52 +72,22 @@ static struct psr_drv *find_psr_by_encoder(struct drm_encoder *encoder)
    return psr;
    }

    -static void psr_set_state_locked(struct psr_drv *psr, enum psr_state state)
    +static int psr_set_state_locked(struct psr_drv *psr, bool enable)
    {
    - /*
    - * Allowed finite state machine:
    - *
    - * PSR_ENABLE < = = = = = > PSR_FLUSH
    - * | ^ |
    - * | | |
    - * v | |
    - * PSR_DISABLE < - - - - - - - - -
    - */
    - if (state == psr->state || !psr->active)
    - return;
    -
    - /* Already disabled in flush, change the state, but not the hardware */
    - if (state == PSR_DISABLE && psr->state == PSR_FLUSH) {
    - psr->state = state;
    - return;
    - }
    + int ret;

    - /* Actually commit the state change to hardware */
    - switch (state) {
    - case PSR_ENABLE:
    - if (psr->set(psr->encoder, true))
    - return;
    - break;
    -
    - case PSR_DISABLE:
    - case PSR_FLUSH:
    - if (psr->set(psr->encoder, false))
    - return;
    - break;
    -
    - default:
    - pr_err("%s: Unknown state %d\n", __func__, state);
    - return;
    - }
    + if (!psr->active)
    + return -EINVAL;

    - psr->state = state;
    -}
    + if (enable == psr->enabled)
    + return 0;

    -static void psr_set_state(struct psr_drv *psr, enum psr_state state)
    -{
    - mutex_lock(&psr->lock);
    - psr_set_state_locked(psr, state);
    - mutex_unlock(&psr->lock);
    + ret = psr->set(psr->encoder, enable);
    + if (ret)
    + return ret;
    +
    + psr->enabled = enable;
    + return 0;
    }

    static void psr_flush_handler(struct work_struct *work)
    @@ -131,10 +95,8 @@ static void psr_flush_handler(struct work_struct *work)
    struct psr_drv *psr = container_of(to_delayed_work(work),
    struct psr_drv, flush_work);

    - /* If the state has changed since we initiated the flush, do nothing */
    mutex_lock(&psr->lock);
    - if (psr->state == PSR_FLUSH)
    - psr_set_state_locked(psr, PSR_ENABLE);
    + psr_set_state_locked(psr, true);
    mutex_unlock(&psr->lock);
    }

    @@ -176,6 +138,7 @@ int rockchip_drm_psr_deactivate(struct drm_encoder *encoder)

    mutex_lock(&psr->lock);
    psr->active = false;
    + psr->enabled = false;
    mutex_unlock(&psr->lock);
    cancel_delayed_work_sync(&psr->flush_work);
    cancel_work_sync(&psr->disable_work);
    @@ -187,8 +150,12 @@ EXPORT_SYMBOL(rockchip_drm_psr_deactivate);
    static void rockchip_drm_do_flush(struct psr_drv *psr)
    {
    cancel_delayed_work_sync(&psr->flush_work);
    - psr_set_state(psr, PSR_FLUSH);
    - mod_delayed_work(system_wq, &psr->flush_work, PSR_FLUSH_TIMEOUT_MS);
    +
    + mutex_lock(&psr->lock);
    + if (!psr_set_state_locked(psr, false))
    + mod_delayed_work(system_wq, &psr->flush_work,
    + PSR_FLUSH_TIMEOUT_MS);
    + mutex_unlock(&psr->lock);
    }

    /**
    @@ -355,8 +322,8 @@ int rockchip_drm_psr_register(struct drm_encoder *encoder,
    INIT_WORK(&psr->disable_work, psr_disable_handler);
    mutex_init(&psr->lock);

    - psr->active = true;
    - psr->state = PSR_DISABLE;
    + psr->active = false;
    + psr->enabled = false;
    psr->encoder = encoder;
    psr->set = psr_set;

    --
    2.16.1
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