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Subject: Re: [PATCH v6 26/30] drm/rockchip: psr: Avoid redundant calls to
 .set() callback
To:     Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        architt@codeaurora.org, inki.dae@samsung.com,
        thierry.reding@gmail.com, hjc@rock-chips.com,
        seanpaul@chromium.org, airlied@linux.ie, tfiga@chromium.org,
        heiko@sntech.de
Cc:     dri-devel@lists.freedesktop.org, dianders@chromium.org,
        ykk@rock-chips.com, kernel@collabora.com, m.szyprowski@samsung.com,
        linux-samsung-soc@vger.kernel.org, jy0922.shim@samsung.com,
        rydberg@bitmath.org, krzk@kernel.org,
        linux-rockchip@lists.infradead.org, kgene@kernel.org,
        linux-input@vger.kernel.org, orjan.eide@arm.com,
        wxt@rock-chips.com, jeffy.chen@rock-chips.com,
        linux-arm-kernel@lists.infradead.org, mark.yao@rock-chips.com,
        wzz@rock-chips.com, hl@rock-chips.com, jingoohan1@gmail.com,
        sw0312.kim@samsung.com, linux-kernel@vger.kernel.org,
        kyungmin.park@samsung.com, Laurent.pinchart@ideasonboard.com,
        kuankuan.y@gmail.com, hshi@chromium.org
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <c6a89199-a5e0-abad-3e53-3ef12da076b9@samsung.com>
Date:   Mon, 16 Apr 2018 11:06:49 +0200
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On 05.04.2018 11:49, Enric Balletbo i Serra wrote:
> 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.

This phrase has no corresponding part in the patch.

>
> 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.

ditto

>
> Signed-off-by: Kristian H. Kristensen <hoegsberg@chromium.org>
> Signed-off-by: Tomasz Figa <tfiga@chromium.org>

Original author should be first, 1st line of the patch "From:...."
suggests it should be Tomasz.

Regards
Andrzej

> 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;
>